# Migrating to a Newer Yocto Project Release

This chapter provides information you can use to migrate work to a newer Yocto Project release. You can find the same information in the release notes for a given release.

## General Migration Considerations

Some considerations are not tied to a specific Yocto Project release. This section presents information you should consider when migrating to any new Yocto Project release.

- Dealing with Customized Recipes: Issues could arise if you take older recipes that contain customizations and simply copy them forward expecting them to work after you migrate to new Yocto Project metadata. For example, suppose you have a recipe in your layer that is a customized version of a core recipe copied from the earlier release, rather than through the use of an append file. When you migrate to a newer version of Yocto Project, the metadata (e.g. perhaps an include file used by the recipe) could have changed in a way that would break the build. Say, for example, a function is removed from an include file and the customized recipe tries to call that function.

  You could "forward-port" all your customizations in your recipe so that everything works for the new release. However, this is not the optimal solution as you would have to repeat this process with each new release if changes occur that give rise to problems.

  The better solution (where practical) is to use append files (`*.bbappend`) to capture any customizations you want to make to a recipe. Doing so, isolates your changes from the main recipe making them much more manageable. However, sometimes it is not practical to use an append file. A good example of this is when introducing a newer or older version of a recipe in another layer.

- Updating Append Files: Since append files generally only contain your customizations, they often do not need to be adjusted for new releases. However, if the `.bbappend` file is specific to a particular version of the recipe (i.e. its name does not use the % wildcard) and the version of the recipe to which it is appending has changed, then you will at a minimum need to rename the append file to match the name of the recipe file. A mismatch between an append file and its corresponding recipe file (`.bb`) will trigger an error during parsing.

  Depending on the type of customization the append file applies, other incompatibilities might occur when you upgrade. For example, if your append file applies a patch and the recipe to which it is appending is updated to a newer version, the patch might no longer apply. If this is the case and assuming the patch is still needed, you must modify the patch file so that it does apply.

## Moving to the Yocto Project 1.3 Release

This section provides migration information for moving to the Yocto Project 1.3 Release from the prior release.

### Local Configuration

Differences include changes for `SSTATE_MIRRORS` and `bblayers.conf`.

#### SSTATE_MIRRORS

The shared state cache (sstate-cache), as pointed to by `SSTATE_DIR`, by default now has two-character subdirectories to prevent issues arising from too many files in the same directory. Also, native sstate-cache packages, which are built to run on the host system, will go into a subdirectory named using the distro ID string. If you copy the newly structured sstate-cache to a mirror location (either local or remote) and then point to it in `SSTATE_MIRRORS`, you need to append "PATH" to the end of the mirror URL so that the path used by BitBake before the mirror substitution is appended to the path used to access the mirror. Here is an example:

         SSTATE_MIRRORS = "file://.* http://someserver.tld/share/sstate/PATH"

#### bblayers.conf

The `meta-yocto` layer consists of two parts that correspond to the Poky reference distribution and the reference hardware Board Support Packages (BSPs), respectively: `meta-yocto` and `meta-yocto-bsp`. When running BitBake for the first time after upgrading, your `conf/bblayers.conf` file will be updated to handle this change and you will be asked to re-run or restart for the changes to take effect.

### Recipes

Differences include changes for the following:

- Python function whitespace

- `proto=` in `SRC_URI`

- `nativesdk`

- Task recipes

- `IMAGE_FEATURES`

- Removed recipes

#### Python Function Whitespace

All Python functions must now use four spaces for indentation. Previously, an inconsistent mix of spaces and tabs existed, which made extending these functions using `_append` or `_prepend` complicated given that Python treats whitespace as syntactically significant. If you are defining or extending any Python functions (e.g. `populate_packages`, `do_unpack`, `do_patch` and so forth) in custom recipes or classes, you need to ensure you are using consistent four-space indentation.

#### proto= in SRC_URI

Any use of `proto=` in `SRC_URI` needs to be changed to `protocol=`. In particular, this applies to the following URIs:

- `svn://`

- `bzr://`

- `hg://`

- `osc://`

Other URIs were already using `protocol=`. This change improves consistency.

#### nativesdk

The suffix `nativesdk` is now implemented as a prefix, which simplifies a lot of the packaging code for `nativesdk` recipes. All custom `nativesdk` recipes, which are relocatable packages that are native to `SDK_ARCH`, and any references need to be updated to use `nativesdk-*` instead of `*-nativesdk`.

#### Task Recipes

"Task" recipes are now known as "Package groups" and have been renamed from `task-*.bb` to `packagegroup-*.bb`. Existing references to the previous `task-*` names should work in most cases as there is an automatic upgrade path for most packages. However, you should update references in your own recipes and configurations as they could be removed in future releases. You should also rename any custom `task-*` recipes to `packagegroup-*`, and change them to inherit `packagegroup` instead of `task`, as well as taking the opportunity to remove anything now handled by `packagegroup.bbclass`, such as providing `-dev` and `-dbg` packages, setting `LIC_FILES_CHKSUM`, and so forth. See the "`packagegroup.bbclass`" section for further details.

#### IMAGE_FEATURES

Image recipes that previously included "apps-console-core" in `IMAGE_FEATURES` should now include "splash" instead to enable the boot-up splash screen. Retaining "apps-console-core" will still include the splash screen but generates a warning. The "apps-x11-core" and "apps-x11-games" `IMAGE_FEATURES` features have been removed.

#### Removed Recipes

The following recipes have been removed. For most of them, it is unlikely that you would have any references to them in your own Metadata. However, you should check your metadata against this list to be sure:

- `libx11-trim`: Replaced by `libx11`, which has a negligible size difference with modern Xorg.

- `xserver-xorg-lite`: Use `xserver-xorg`, which has a negligible size difference when DRI and GLX modules are not installed.

- `xserver-kdrive`: Effectively unmaintained for many years.

- `mesa-xlib`: No longer serves any purpose.

- `galago`: Replaced by telepathy.

- `gail`: Functionality was integrated into GTK+ 2.13.

- `eggdbus`: No longer needed.

- `gcc-*-intermediate`: The build has been restructured to avoid the need for this step.

- `libgsmd`: Unmaintained for many years. Functionality now provided by `ofono` instead.

- contacts, dates, tasks, eds-tools: Largely unmaintained PIM application suite. It has been moved to `meta-gnome` in `meta-openembedded`.

In addition to the previously listed changes, the `meta-demoapps` directory has also been removed because the recipes in it were not being maintained and many had become obsolete or broken. Additionally, these recipes were not parsed in the default configuration. Many of these recipes are already provided in an updated and maintained form within the OpenEmbedded community layers such as `meta-oe` and `meta-gnome`. For the remainder, you can now find them in the `meta-extras` repository, which is in the Yocto Project Source Repositories.

### Linux Kernel Naming

The naming scheme for kernel output binaries has been changed to now include `PE` as part of the filename:

         KERNEL_IMAGE_BASE_NAME ?= "${KERNEL_IMAGETYPE}-${PE}-${PV}-${PR}-${MACHINE}-${DATETIME}"

Because the `PE` variable is not set by default, these binary files could result with names that include two dash characters. Here is an example:

         bzImage--3.10.9+git0+cd502a8814_7144bcc4b8-r0-qemux86-64-20130830085431.bin

## Moving to the Yocto Project 1.4 Release

This section provides migration information for moving to the Yocto Project 1.4 Release from the prior release.

### BitBake

Differences include the following:

- Comment Continuation: If a comment ends with a line continuation (\) character, then the next line must also be a comment. Any instance where this is not the case, now triggers a warning. You must either remove the continuation character, or be sure the next line is a comment.

- Package Name Overrides: The runtime package specific variables `RDEPENDS`, `RRECOMMENDS`, `RSUGGESTS`, `RPROVIDES`, `RCONFLICTS`, `RREPLACES`, `FILES`, `ALLOW_EMPTY`, and the pre, post, install, and uninstall script functions `pkg_preinst`, `pkg_postinst`, `pkg_prerm`, and `pkg_postrm` should always have a package name override. For example, use `RDEPENDS_${PN}` for the main package instead of `RDEPENDS`. BitBake uses more strict checks when it parses recipes.

### Build Behavior

Differences include the following:

- Shared State Code: The shared state code has been optimized to avoid running unnecessary tasks. For example, the following no longer populates the target sysroot since that is not necessary:

           $ bitbake -c rootfs some-image

  Instead, the system just needs to extract the output package contents, re-create the packages, and construct the root filesystem. This change is unlikely to cause any problems unless you have missing declared dependencies.

- Scanning Directory Names: When scanning for files in `SRC_URI`, the build system now uses `FILESOVERRIDES` instead of `OVERRIDES` for the directory names. In general, the values previously in `OVERRIDES` are now in `FILESOVERRIDES` as well. However, if you relied upon an additional value you previously added to `OVERRIDES`, you might now need to add it to `FILESOVERRIDES` unless you are already adding it through the `MACHINEOVERRIDES` or `DISTROOVERRIDES` variables, as appropriate. For more related changes, see the "Variables" section.

### Proxies and Fetching Source

A new `oe-git-proxy` script has been added to replace previous methods of handling proxies and fetching source from Git. See the `meta-yocto/conf/site.conf.sample` file for information on how to use this script.

### Custom Interfaces File (netbase change)

If you have created your own custom `etc/network/interfaces` file by creating an append file for the `netbase` recipe, you now need to create an append file for the `init-ifupdown` recipe instead, which you can find in the Source Directory at `meta/recipes-core/init-ifupdown`. For information on how to use append files, see the "Using .bbappend Files" section in the Yocto Project Development Tasks Manual.

### Remote Debugging

Support for remote debugging with the Eclipse IDE is now separated into an image feature (`eclipse-debug`) that corresponds to the `packagegroup-core-eclipse-debug` package group. Previously, the debugging feature was included through the `tools-debug` image feature, which corresponds to the `packagegroup-core-tools-debug` package group.

### Variables

The following variables have changed:

- `SANITY_TESTED_DISTROS`: This variable now uses a distribution ID, which is composed of the host distributor ID followed by the release. Previously, `SANITY_TESTED_DISTROS` was composed of the description field. For example, "Ubuntu 12.10" becomes "Ubuntu-12.10". You do not need to worry about this change if you are not specifically setting this variable, or if you are specifically setting it to "".

- `SRC_URI`: The `${``PN``}`, `${``PF``}`, `${``P``}`, and `FILE_DIRNAME` directories have been dropped from the default value of the `FILESPATH` variable, which is used as the search path for finding files referred to in `SRC_URI`. If you have a recipe that relied upon these directories, which would be unusual, then you will need to add the appropriate paths within the recipe or, alternatively, rearrange the files. The most common locations are still covered by `${BP}`, `${BPN}`, and "files", which all remain in the default value of `FILESPATH`.

### Target Package Management with RPM

If runtime package management is enabled and the RPM backend is selected, Smart is now installed for package download, dependency resolution, and upgrades instead of Zypper. For more information on how to use Smart, run the following command on the target:

         smart --help

### Recipes Moved

The following recipes were moved from their previous locations because they are no longer used by anything in the OpenEmbedded-Core:

- `clutter-box2d`: Now resides in the `meta-oe` layer.

- `evolution-data-server`: Now resides in the `meta-gnome` layer.

- `gthumb`: Now resides in the `meta-gnome` layer.

- `gtkhtml2`: Now resides in the `meta-oe` layer.

- `gupnp`: Now resides in the `meta-multimedia` layer.

- `gypsy`: Now resides in the `meta-oe` layer.

- `libcanberra`: Now resides in the `meta-gnome` layer.

- `libgdata`: Now resides in the `meta-gnome` layer.

- `libmusicbrainz`: Now resides in the `meta-multimedia` layer.

- `metacity`: Now resides in the `meta-gnome` layer.

- `polkit`: Now resides in the `meta-oe` layer.

- `zeroconf`: Now resides in the `meta-networking` layer.

### Removals and Renames

The following list shows what has been removed or renamed:

- `evieext`: Removed because it has been removed from `xserver` since 2008.

- Gtk+ DirectFB: Removed support because upstream Gtk+ no longer supports it as of version 2.18.

- `libxfontcache / xfontcacheproto`: Removed because they were removed from the Xorg server in 2008.

- `libxp / libxprintapputil / libxprintutil / printproto`: Removed because the XPrint server was removed from Xorg in 2008.

- `libxtrap / xtrapproto`: Removed because their functionality was broken upstream.

- linux-yocto 3.0 kernel: Removed with linux-yocto 3.8 kernel being added. The linux-yocto 3.2 and linux-yocto 3.4 kernels remain as part of the release.

- `lsbsetup`: Removed with functionality now provided by `lsbtest`.

- `matchbox-stroke`: Removed because it was never more than a proof-of-concept.

- `matchbox-wm-2 / matchbox-theme-sato-2`: Removed because they are not maintained. However, `matchbox-wm` and `matchbox-theme-sato` are still provided.

- `mesa-dri`: Renamed to `mesa`.

- `mesa-xlib`: Removed because it was no longer useful.

- `mutter`: Removed because nothing ever uses it and the recipe is very old.

- `orinoco-conf`: Removed because it has become obsolete.

- `update-modules`: Removed because it is no longer used. The kernel module `postinstall` and `postrm` scripts can now do the same task without the use of this script.

- `web`: Removed because it is not maintained. Superseded by `web-webkit`.

- `xf86bigfontproto`: Removed because upstream it has been disabled by default since 2007. Nothing uses `xf86bigfontproto`.

- `xf86rushproto`: Removed because its dependency in `xserver` was spurious and it was removed in 2005.

- `zypper / libzypp / sat-solver`: Removed and been functionally replaced with Smart (`python-smartpm`) when RPM packaging is used and package management is enabled on the target.

## Moving to the Yocto Project 1.5 Release

This section provides migration information for moving to the Yocto Project 1.5 Release from the prior release.

### Host Dependency Changes

The OpenEmbedded build system now has some additional requirements on the host system:

- Python 2.7.3+

- Tar 1.24+

- Git 1.7.8+

- Patched version of Make if you are using 3.82. Most distributions that provide Make 3.82 use the patched version.

If the Linux distribution you are using on your build host does not provide packages for these, you can install and use the Buildtools tarball, which provides an SDK-like environment containing them.

For more information on this requirement, see the "Required Git, tar, Python and gcc Versions" section.

### `atom-pc` Board Support Package (BSP)

The `atom-pc` hardware reference BSP has been replaced by a `genericx86` BSP. This BSP is not necessarily guaranteed to work on all x86 hardware, but it will run on a wider range of systems than the `atom-pc` did.

Additionally, a `genericx86-64` BSP has been added for 64-bit Atom systems.

### BitBake

The following changes have been made that relate to BitBake:

- BitBake now supports a `_remove` operator. The addition of this operator means you will have to rename any items in recipe space (functions, variables) whose names currently contain `_remove_` or end with `_remove` to avoid unexpected behavior.

- BitBake's global method pool has been removed. This method is not particularly useful and led to clashes between recipes containing functions that had the same name.

- The "none" server backend has been removed. The "process" server backend has been serving well as the default for a long time now.

- The `bitbake-runtask` script has been removed.

- `${``P``}` and `${``PF``}` are no longer added to `PROVIDES` by default in `bitbake.conf`. These version-specific `PROVIDES` items were seldom used. Attempting to use them could result in two versions being built simultaneously rather than just one version due to the way BitBake resolves dependencies.

### QA Warnings

The following changes have been made to the package QA checks:

- If you have customized `ERROR_QA` or `WARN_QA` values in your configuration, check that they contain all of the issues that you wish to be reported. Previous Yocto Project versions contained a bug that meant that any item not mentioned in `ERROR_QA` or `WARN_QA` would be treated as a warning. Consequently, several important items were not already in the default value of `WARN_QA`. All of the possible QA checks are now documented in the "`insane.bbclass`" section.

- An additional QA check has been added to check if `/usr/share/info/dir` is being installed. Your recipe should delete this file within `do_install` if "make install" is installing it.

- If you are using the buildhistory class, the check for the package version going backwards is now controlled using a standard QA check. Thus, if you have customized your `ERROR_QA` or `WARN_QA` values and still wish to have this check performed, you should add "version-going-backwards" to your value for one or the other variables depending on how you wish it to be handled. See the documented QA checks in the "`insane.bbclass`" section.

### Directory Layout Changes

The following directory changes exist:

- Output SDK installer files are now named to include the image name and tuning architecture through the `SDK_NAME` variable.

- Images and related files are now installed into a directory that is specific to the machine, instead of a parent directory containing output files for multiple machines. The `DEPLOY_DIR_IMAGE` variable continues to point to the directory containing images for the current `MACHINE` and should be used anywhere there is a need to refer to this directory. The `runqemu` script now uses this variable to find images and kernel binaries and will use BitBake to determine the directory. Alternatively, you can set the `DEPLOY_DIR_IMAGE` variable in the external environment.

- When buildhistory is enabled, its output is now written under the Build Directory rather than `TMPDIR`. Doing so makes it easier to delete `TMPDIR` and preserve the build history. Additionally, data for produced SDKs is now split by `IMAGE_NAME`.

- The `pkgdata` directory produced as part of the packaging process has been collapsed into a single machine-specific directory. This directory is located under `sysroots` and uses a machine-specific name (i.e. `tmp/sysroots/machine/pkgdata`).

### Shortened Git `SRCREV` Values

BitBake will now shorten revisions from Git repositories from the normal 40 characters down to 10 characters within `SRCPV` for improved usability in path and file names. This change should be safe within contexts where these revisions are used because the chances of spatially close collisions is very low. Distant collisions are not a major issue in the way the values are used.

### `IMAGE_FEATURES`

The following changes have been made that relate to `IMAGE_FEATURES`:

- The value of `IMAGE_FEATURES` is now validated to ensure invalid feature items are not added. Some users mistakenly add package names to this variable instead of using `IMAGE_INSTALL` in order to have the package added to the image, which does not work. This change is intended to catch those kinds of situations. Valid `IMAGE_FEATURES` are drawn from `PACKAGE_GROUP` definitions, `COMPLEMENTARY_GLOB` and a new "validitems" varflag on `IMAGE_FEATURES`. The "validitems" varflag change allows additional features to be added if they are not provided using the previous two mechanisms.

- The previously deprecated "apps-console-core" `IMAGE_FEATURES` item is no longer supported. Add "splash" to `IMAGE_FEATURES` if you wish to have the splash screen enabled, since this is all that apps-console-core was doing.

### `/run`

The `/run` directory from the Filesystem Hierarchy Standard 3.0 has been introduced. You can find some of the implications for this change here. The change also means that recipes that install files to `/var/run` must be changed. You can find a guide on how to make these changes here.

### Removal of Package Manager Database Within Image Recipes

The image `core-image-minimal` no longer adds `remove_packaging_data_files` to `ROOTFS_POSTPROCESS_COMMAND`. This addition is now handled automatically when "package-management" is not in `IMAGE_FEATURES`. If you have custom image recipes that make this addition, you should remove the lines, as they are not needed and might interfere with correct operation of postinstall scripts.

### Images Now Rebuild Only on Changes Instead of Every Time

The `do_rootfs` and other related image construction tasks are no longer marked as "nostamp". Consequently, they will only be re-executed when their inputs have changed. Previous versions of the OpenEmbedded build system always rebuilt the image when requested rather when necessary.

### Task Recipes

The previously deprecated `task.bbclass` has now been dropped. For recipes that previously inherited from this class, you should rename them from `task-*` to `packagegroup-*` and inherit packagegroup instead.

For more information, see the "`packagegroup.bbclass`" section.

### BusyBox

By default, we now split BusyBox into two binaries: one that is suid root for those components that need it, and another for the rest of the components. Splitting BusyBox allows for optimization that eliminates the `tinylogin` recipe as recommended by upstream. You can disable this split by setting `BUSYBOX_SPLIT_SUID` to "0".

### Automated Image Testing

A new automated image testing framework has been added through the `testimage.bbclass` class. This framework replaces the older `imagetest-qemu` framework.

You can learn more about performing automated image tests in the "Performing Automated Runtime Testing" section in the Yocto Project Development Tasks Manual.

### Build History

Following are changes to Build History:

- Installed package sizes: `installed-package-sizes.txt` for an image now records the size of the files installed by each package instead of the size of each compressed package archive file.

- The dependency graphs (`depends*.dot`) now use the actual package names instead of replacing dashes, dots and plus signs with underscores.

- The `buildhistory-diff` and `buildhistory-collect-srcrevs` utilities have improved command-line handling. Use the `--help` option for each utility for more information on the new syntax.

For more information on Build History, see the "Maintaining Build Output Quality" section in the Yocto Project Development Tasks Manual.

### `udev`

Following are changes to `udev`:

- `udev` no longer brings in `udev-extraconf` automatically through `RRECOMMENDS`, since this was originally intended to be optional. If you need the extra rules, then add `udev-extraconf` to your image.

- `udev` no longer brings in `pciutils-ids` or `usbutils-ids` through `RRECOMMENDS`. These are not needed by `udev` itself and removing them saves around 350KB.

### Removed and Renamed Recipes

- The `linux-yocto` 3.2 kernel has been removed.

- `libtool-nativesdk` has been renamed to `nativesdk-libtool`.

- `tinylogin` has been removed. It has been replaced by a suid portion of Busybox. See the "BusyBox" section for more information.

- `external-python-tarball` has been renamed to `buildtools-tarball`.

- `web-webkit` has been removed. It has been functionally replaced by `midori`.

- `imake` has been removed. It is no longer needed by any other recipe.

- `transfig-native` has been removed. It is no longer needed by any other recipe.

- `anjuta-remote-run` has been removed. Anjuta IDE integration has not been officially supported for several releases.

### Other Changes

Following is a list of short entries describing other changes:

- `run-postinsts`: Make this generic.

- `base-files`: Remove the unnecessary `media/`xxx directories.

- `alsa-state`: Provide an empty `asound.conf` by default.

- `classes/image`: Ensure `BAD_RECOMMENDATIONS` supports pre-renamed package names.

- `classes/rootfs_rpm`: Implement `BAD_RECOMMENDATIONS` for RPM.

- `systemd`: Remove `systemd_unitdir` if `systemd` is not in `DISTRO_FEATURES`.

- `systemd`: Remove `init.d` dir if `systemd` unit file is present and `sysvinit` is not a distro feature.

- `libpam`: Deny all services for the `OTHER` entries.

- `image.bbclass`: Move `runtime_mapping_rename` to avoid conflict with `multilib`. See `YOCTO #4993` in Bugzilla for more information.

- `linux-dtb`: Use kernel build system to generate the `dtb` files.

- `kern-tools`: Switch from guilt to new `kgit-s2q` tool.

## Moving to the Yocto Project 1.6 Release

This section provides migration information for moving to the Yocto Project 1.6 Release from the prior release.

### `archiver` Class

The `archiver` class has been rewritten and its configuration has been simplified. For more details on the source archiver, see the "Maintaining Open Source License Compliance During Your Product's Lifecycle" section in the Yocto Project Development Tasks Manual.

### Packaging Changes

The following packaging changes have been made:

- The `binutils` recipe no longer produces a `binutils-symlinks` package. `update-alternatives` is now used to handle the preferred `binutils` variant on the target instead.

- The tc (traffic control) utilities have been split out of the main `iproute2` package and put into the `iproute2-tc` package.

- The `gtk-engines` schemas have been moved to a dedicated `gtk-engines-schemas` package.

- The `armv7a` with thumb package architecture suffix has changed. The suffix for these packages with the thumb optimization enabled is "t2" as it should be. Use of this suffix was not the case in the 1.5 release. Architecture names will change within package feeds as a result.

### BitBake

The following changes have been made to BitBake.

#### Matching Branch Requirement for Git Fetching

When fetching source from a Git repository using `SRC_URI`, BitBake will now validate the `SRCREV` value against the branch. You can specify the branch using the following form:

         SRC_URI = "git://server.name/repository;branch=branchname"

If you do not specify a branch, BitBake looks in the default "master" branch.

Alternatively, if you need to bypass this check (e.g. if you are fetching a revision corresponding to a tag that is not on any branch), you can add ";nobranch=1" to the end of the URL within `SRC_URI`.

#### Python Definition substitutions

BitBake had some previously deprecated Python definitions within its `bb` module removed. You should use their sub-module counterparts instead:

- `bb.MalformedUrl`: Use `bb.fetch.MalformedUrl`.

- `bb.encodeurl`: Use `bb.fetch.encodeurl`.

- `bb.decodeurl`: Use `bb.fetch.decodeurl`

- `bb.mkdirhier`: Use `bb.utils.mkdirhier`.

- `bb.movefile`: Use `bb.utils.movefile`.

- `bb.copyfile`: Use `bb.utils.copyfile`.

- `bb.which`: Use `bb.utils.which`.

- `bb.vercmp_string`: Use `bb.utils.vercmp_string`.

- `bb.vercmp`: Use `bb.utils.vercmp`.

#### SVK Fetcher

The SVK fetcher has been removed from BitBake.

#### Console Output Error Redirection

The BitBake console UI will now output errors to `stderr` instead of `stdout`. Consequently, if you are piping or redirecting the output of `bitbake` to somewhere else, and you wish to retain the errors, you will need to add `2>&1` (or something similar) to the end of your `bitbake` command line.

#### `task-`taskname Overrides

`task-`taskname overrides have been adjusted so that tasks whose names contain underscores have the underscores replaced by hyphens for the override so that they now function properly. For example, the task override for `do_populate_sdk` is `task-populate-sdk`.

### Changes to Variables

The following variables have changed. For information on the OpenEmbedded build system variables, see the "Variables Glossary" Chapter.

#### `TMPDIR`

`TMPDIR` can no longer be on an NFS mount. NFS does not offer full POSIX locking and inode consistency and can cause unexpected issues if used to store `TMPDIR`.

The check for this occurs on startup. If `TMPDIR` is detected on an NFS mount, an error occurs.

#### `PRINC`

The `PRINC` variable has been deprecated and triggers a warning if detected during a build. For `PR` increments on changes, use the PR service instead. You can find out more about this service in the "Working With a PR Service" section in the Yocto Project Development Tasks Manual.

#### `IMAGE_TYPES`

The "sum.jffs2" option for `IMAGE_TYPES` has been replaced by the "jffs2.sum" option, which fits the processing order.

#### `COPY_LIC_MANIFEST`

The `COPY_LIC_MANIFEST` variable must now be set to "1" rather than any value in order to enable it.

#### `COPY_LIC_DIRS`

The `COPY_LIC_DIRS` variable must now be set to "1" rather than any value in order to enable it.

#### `PACKAGE_GROUP`

The `PACKAGE_GROUP` variable has been renamed to `FEATURE_PACKAGES` to more accurately reflect its purpose. You can still use `PACKAGE_GROUP` but the OpenEmbedded build system produces a warning message when it encounters the variable.

#### Preprocess and Post Process Command Variable Behavior

The following variables now expect a semicolon separated list of functions to call and not arbitrary shell commands:

         ROOTFS_PREPROCESS_COMMAND
         ROOTFS_POSTPROCESS_COMMAND
         SDK_POSTPROCESS_COMMAND
         POPULATE_SDK_POST_TARGET_COMMAND
         POPULATE_SDK_POST_HOST_COMMAND
         IMAGE_POSTPROCESS_COMMAND
         IMAGE_PREPROCESS_COMMAND
         ROOTFS_POSTUNINSTALL_COMMAND
         ROOTFS_POSTINSTALL_COMMAND

For migration purposes, you can simply wrap shell commands in a shell function and then call the function. Here is an example:

         my_postprocess_function() {
            echo "hello" > ${IMAGE_ROOTFS}/hello.txt
         }
         ROOTFS_POSTPROCESS_COMMAND += "my_postprocess_function; "

### Package Test (ptest)

Package Tests (ptest) are built but not installed by default. For information on using Package Tests, see the "Testing Packages with ptest" section in the Yocto Project Development Tasks Manual. For information on the `ptest` class, see the "`ptest.bbclass`" section.

### Build Changes

Separate build and source directories have been enabled by default for selected recipes where it is known to work (a whitelist) and for all recipes that inherit the `cmake` class. In future releases the `autotools` class will enable a separate build directory by default as well. Recipes building Autotools-based software that fails to build with a separate build directory should be changed to inherit from the `autotools-brokensep` class instead of the `autotools` or `autotools_stage`classes.

### `qemu-native`

`qemu-native` now builds without SDL-based graphical output support by default. The following additional lines are needed in your `local.conf` to enable it:

         PACKAGECONFIG_pn-qemu-native = "sdl"
         ASSUME_PROVIDED += "libsdl-native"

The default `local.conf` contains these statements. Consequently, if you are building a headless system and using a default `local.conf` file, you will need comment these two lines out.

### `core-image-basic`

`core-image-basic` has been renamed to `core-image-full-cmdline`.

In addition to `core-image-basic` being renamed, `packagegroup-core-basic` has been renamed to `packagegroup-core-full-cmdline` to match.

### Licensing

The top-level `LICENSE` file has been changed to better describe the license of the various components of OE-Core. However, the licensing itself remains unchanged.

Normally, this change would not cause any side-effects. However, some recipes point to this file within `LIC_FILES_CHKSUM` (as `${COREBASE}/LICENSE`) and thus the accompanying checksum must be changed from 3f40d7994397109285ec7b81fdeb3b58 to 4d92cd373abda3937c2bc47fbc49d690. A better alternative is to have `LIC_FILES_CHKSUM` point to a file describing the license that is distributed with the source that the recipe is building, if possible, rather than pointing to `${COREBASE}/LICENSE`.

### `CFLAGS` Options

The "-fpermissive" option has been removed from the default `CFLAGS` value. You need to take action on individual recipes that fail when building with this option. You need to either patch the recipes to fix the issues reported by the compiler, or you need to add "-fpermissive" to `CFLAGS` in the recipes.

### Custom Image Output Types

Custom image output types, as selected using `IMAGE_FSTYPES`, must declare their dependencies on other image types (if any) using a new `IMAGE_TYPEDEP` variable.

### Tasks

The `do_package_write` task has been removed. The task is no longer needed.

### `update-alternative` Provider

The default `update-alternatives` provider has been changed from `opkg` to `opkg-utils`. This change resolves some troublesome circular dependencies. The runtime package has also been renamed from `update-alternatives-cworth` to `update-alternatives-opkg`.

### `virtclass` Overrides

The `virtclass` overrides are now deprecated. Use the equivalent class overrides instead (e.g. `virtclass-native` becomes `class-native`.)

### Removed and Renamed Recipes

The following recipes have been removed:

- `packagegroup-toolset-native` - This recipe is largely unused.

- `linux-yocto-3.8` - Support for the Linux yocto 3.8 kernel has been dropped. Support for the 3.10 and 3.14 kernels have been added with the `linux-yocto-3.10` and `linux-yocto-3.14` recipes.

- `ocf-linux` - This recipe has been functionally replaced using `cryptodev-linux`.

- `genext2fs` - `genext2fs` is no longer used by the build system and is unmaintained upstream.

- `js` - This provided an ancient version of Mozilla's javascript engine that is no longer needed.

- `zaurusd` - The recipe has been moved to the `meta-handheld` layer.

- `eglibc 2.17` - Replaced by the `eglibc 2.19` recipe.

- `gcc 4.7.2` - Replaced by the now stable `gcc 4.8.2`.

- `external-sourcery-toolchain` - this recipe is now maintained in the `meta-sourcery` layer.

- `linux-libc-headers-yocto 3.4+git` - Now using version 3.10 of the `linux-libc-headers` by default.

- `meta-toolchain-gmae` - This recipe is obsolete.

- `packagegroup-core-sdk-gmae` - This recipe is obsolete.

- `packagegroup-core-standalone-gmae-sdk-target` - This recipe is obsolete.

### Removed Classes

The following classes have become obsolete and have been removed:

- `module_strip`

- `pkg_metainfo`

- `pkg_distribute`

- `image-empty`

### Reference Board Support Packages (BSPs)

The following reference BSPs changes occurred:

- The BeagleBoard (`beagleboard`) ARM reference hardware has been replaced by the BeagleBone (`beaglebone`) hardware.

- The RouterStation Pro (`routerstationpro`) MIPS reference hardware has been replaced by the EdgeRouter Lite (`edgerouter`) hardware.

The previous reference BSPs for the `beagleboard` and `routerstationpro` machines are still available in a new `meta-yocto-bsp-old` layer in the Source Repositories at http://git.yoctoproject.org/cgit/cgit.cgi/meta-yocto-bsp-old/.

## Moving to the Yocto Project 1.7 Release

This section provides migration information for moving to the Yocto Project 1.7 Release from the prior release.

### Changes to Setting QEMU `PACKAGECONFIG` Options in `local.conf`

The QEMU recipe now uses a number of `PACKAGECONFIG` options to enable various optional features. The method used to set defaults for these options means that existing `local.conf` files will need to be be modified to append to `PACKAGECONFIG` for `qemu-native` and `nativesdk-qemu` instead of setting it. In other words, to enable graphical output for QEMU, you should now have these lines in `local.conf`:

         PACKAGECONFIG_append_pn-qemu-native = " sdl"
         PACKAGECONFIG_append_pn-nativesdk-qemu = " sdl"

### Minimum Git version

The minimum Git version required on the build host is now 1.7.8 because the `--list` option is now required by BitBake's Git fetcher. As always, if your host distribution does not provide a version of Git that meets this requirement, you can use the `buildtools-tarball` that does. See the "Required Git, tar, Python and gcc Versions" section for more information.

### Autotools Class Changes

The following `autotools` class changes occurred:

- A separate build directory is now used by default: The `autotools` class has been changed to use a directory for building (`B`), which is separate from the source directory (`S`). This is commonly referred to as `B != S`, or an out-of-tree build.

  If the software being built is already capable of building in a directory separate from the source, you do not need to do anything. However, if the software is not capable of being built in this manner, you will need to either patch the software so that it can build separately, or you will need to change the recipe to inherit the `autotools-brokensep` class instead of the `autotools` or `autotools_stage` classes.

- The `--foreign` option is no longer passed to `automake` when running `autoconf`: This option tells `automake` that a particular software package does not follow the GNU standards and therefore should not be expected to distribute certain files such as `ChangeLog`, `AUTHORS`, and so forth. Because the majority of upstream software packages already tell `automake` to enable foreign mode themselves, the option is mostly superfluous. However, some recipes will need patches for this change. You can easily make the change by patching `configure.ac` so that it passes "foreign" to `AM_INIT_AUTOMAKE()`. See this commit for an example showing how to make the patch.

### Binary Configuration Scripts Disabled

Some of the core recipes that package binary configuration scripts now disable the scripts due to the scripts previously requiring error-prone path substitution. Software that links against these libraries using these scripts should use the much more robust `pkg-config` instead. The list of recipes changed in this version (and their configuration scripts) is as follows:

         directfb (directfb-config)
         freetype (freetype-config)
         gpgme (gpgme-config)
         libassuan (libassuan-config)
         libcroco (croco-6.0-config)
         libgcrypt (libgcrypt-config)
         libgpg-error (gpg-error-config)
         libksba (ksba-config)
         libpcap (pcap-config)
         libpcre (pcre-config)
         libpng (libpng-config, libpng16-config)
         libsdl (sdl-config)
         libusb-compat (libusb-config)
         libxml2 (xml2-config)
         libxslt (xslt-config)
         ncurses (ncurses-config)
         neon (neon-config)
         npth (npth-config)
         pth (pth-config)
         taglib (taglib-config)

Additionally, support for `pkg-config` has been added to some recipes in the previous list in the rare cases where the upstream software package does not already provide it.

### `eglibc 2.19` Replaced with `glibc 2.20`

Because `eglibc` and `glibc` were already fairly close, this replacement should not require any significant changes to other software that links to `eglibc`. However, there were a number of minor changes in `glibc 2.20` upstream that could require patching some software (e.g. the removal of the `_BSD_SOURCE` feature test macro).

`glibc 2.20` requires version 2.6.32 or greater of the Linux kernel. Thus, older kernels will no longer be usable in conjunction with it.

For full details on the changes in `glibc 2.20`, see the upstream release notes here.

### Kernel Module Autoloading

The `module_autoload_*` variable is now deprecated and a new `KERNEL_MODULE_AUTOLOAD` variable should be used instead. Also, `module_conf_*` must now be used in conjunction with a new `KERNEL_MODULE_PROBECONF` variable. The new variables no longer require you to specify the module name as part of the variable name. This change not only simplifies usage but also allows the values of these variables to be appropriately incorporated into task signatures and thus trigger the appropriate tasks to re-execute when changed. You should replace any references to `module_autoload_*` with `KERNEL_MODULE_AUTOLOAD`, and add any modules for which `module_conf_*` is specified to `KERNEL_MODULE_PROBECONF`.

### QA Check Changes

The following changes have occurred to the QA check process:

- Additional QA checks `file-rdeps` and `build-deps` have been added in order to verify that file dependencies are satisfied (e.g. package contains a script requiring `/bin/bash`) and build-time dependencies are declared, respectively. For more information, please see the "QA Error and Warning Messages" chapter.

- Package QA checks are now performed during a new `do_package_qa` task rather than being part of the `do_package` task. This allows more parallel execution. This change is unlikely to be an issue except for highly customized recipes that disable packaging tasks themselves by marking them as `noexec`. For those packages, you will need to disable the `do_package_qa` task as well.

- Files being overwritten during the `do_populate_sysroot` task now trigger an error instead of a warning. Recipes should not be overwriting files written to the sysroot by other recipes. If you have these types of recipes, you need to alter them so that they do not overwrite these files.

  You might now receive this error after changes in configuration or metadata resulting in orphaned files being left in the sysroot. If you do receive this error, the way to resolve the issue is to delete your `TMPDIR` or to move it out of the way and then re-start the build. Anything that has been fully built up to that point and does not need rebuilding will be restored from the shared state cache and the rest of the build will be able to proceed as normal.

### Removed Recipes

The following recipes have been removed:

- `x-load`: This recipe has been superseded by U-boot SPL for all Cortex-based TI SoCs. For legacy boards, the `meta-ti` layer, which contains a maintained recipe, should be used instead.

- `ubootchart`: This recipe is obsolete. A `bootchart2` recipe has been added to functionally replace it.

- `linux-yocto 3.4`: Support for the linux-yocto 3.4 kernel has been dropped. Support for the 3.10 and 3.14 kernels remains, while support for version 3.17 has been added.

- `eglibc` has been removed in favor of `glibc`. See the "`eglibc 2.19` Replaced with `glibc 2.20`" section for more information.

### Miscellaneous Changes

The following miscellaneous change occurred:

- The build history feature now writes `build-id.txt` instead of `build-id`. Additionally, `build-id.txt` now contains the full build header as printed by BitBake upon starting the build. You should manually remove old "build-id" files from your existing build history repositories to avoid confusion. For information on the build history feature, see the "Maintaining Build Output Quality" section in the Yocto Project Development Tasks Manual.

## Moving to the Yocto Project 1.8 Release

This section provides migration information for moving to the Yocto Project 1.8 Release from the prior release.

### Removed Recipes

The following recipes have been removed:

- `owl-video`: Functionality replaced by `gst-player`.

- `gaku`: Functionality replaced by `gst-player`.

- `gnome-desktop`: This recipe is now available in `meta-gnome` and is no longer needed.

- `gsettings-desktop-schemas`: This recipe is now available in `meta-gnome` and is no longer needed.

- `python-argparse`: The `argparse` module is already provided in the default Python distribution in a package named `python-argparse`. Consequently, the separate `python-argparse` recipe is no longer needed.

- `telepathy-python, libtelepathy, telepathy-glib, telepathy-idle, telepathy-mission-control`: All these recipes have moved to `meta-oe` and are consequently no longer needed by any recipes in OpenEmbedded-Core.

- `linux-yocto_3.10` and `linux-yocto_3.17`: Support for the linux-yocto 3.10 and 3.17 kernels has been dropped. Support for the 3.14 kernel remains, while support for 3.19 kernel has been added.

- `poky-feed-config-opkg`: This recipe has become obsolete and is no longer needed. Use `distro-feed-config` from `meta-oe` instead.

- `libav 0.8.x`: `libav 9.x` is now used.

- `sed-native`: No longer needed. A working version of `sed` is expected to be provided by the host distribution.

### BlueZ 4.x / 5.x Selection

Proper built-in support for selecting BlueZ 5.x in preference to the default of 4.x now exists. To use BlueZ 5.x, simply add "bluez5" to your `DISTRO_FEATURES` value. If you had previously added append files (`*.bbappend`) to make this selection, you can now remove them.

Additionally, a `bluetooth` class has been added to make selection of the appropriate bluetooth support within a recipe a little easier. If you wish to make use of this class in a recipe, add something such as the following:

         inherit bluetooth
         PACKAGECONFIG ??= "${@bb.utils.contains('DISTRO_FEATURES', 'bluetooth', '${BLUEZ}', '', d)}"
         PACKAGECONFIG[bluez4] = "--enable-bluetooth,--disable-bluetooth,bluez4"
         PACKAGECONFIG[bluez5] = "--enable-bluez5,--disable-bluez5,bluez5"

### Kernel Build Changes

The kernel build process was changed to place the source in a common shared work area and to place build artifacts separately in the source code tree. In theory, migration paths have been provided for most common usages in kernel recipes but this might not work in all cases. In particular, users need to ensure that `${S}` (source files) and `${B}` (build artifacts) are used correctly in functions such as `do_configure` and `do_install`. For kernel recipes that do not inherit from `kernel-yocto` or include `linux-yocto.inc`, you might wish to refer to the `linux.inc` file in the `meta-oe` layer for the kinds of changes you need to make. For reference, here is the commit where the `linux.inc` file in `meta-oe` was updated.

Recipes that rely on the kernel source code and do not inherit the module classes might need to add explicit dependencies on the `do_shared_workdir` kernel task, for example:

         do_configure[depends] += "virtual/kernel:do_shared_workdir"

### SSL 3.0 is Now Disabled in OpenSSL

SSL 3.0 is now disabled when building OpenSSL. Disabling SSL 3.0 avoids any lingering instances of the POODLE vulnerability. If you feel you must re-enable SSL 3.0, then you can add an append file (`*.bbappend`) for the `openssl` recipe to remove "-no-ssl3" from `EXTRA_OECONF`.

### Default Sysroot Poisoning

`gcc's` default sysroot and include directories are now "poisoned". In other words, the sysroot and include directories are being redirected to a non-existent location in order to catch when host directories are being used due to the correct options not being passed. This poisoning applies both to the cross-compiler used within the build and to the cross-compiler produced in the SDK.

If this change causes something in the build to fail, it almost certainly means the various compiler flags and commands are not being passed correctly to the underlying piece of software. In such cases, you need to take corrective steps.

### Rebuild Improvements

Changes have been made to the `base`, `autotools`, and `cmake` classes to clean out generated files when the `do_configure` task needs to be re-executed.

One of the improvements is to attempt to run "make clean" during the `do_configure` task if a `Makefile` exists. Some software packages do not provide a working clean target within their make files. If you have such recipes, you need to set `CLEANBROKEN` to "1" within the recipe, for example:

         CLEANBROKEN = "1"

### QA Check and Validation Changes

The following QA Check and Validation Changes have occurred:

- Usage of `PRINC` previously triggered a warning. It now triggers an error. You should remove any remaining usage of `PRINC` in any recipe or append file.

- An additional QA check has been added to detect usage of `${D}` in `FILES` values where `D` values should not be used at all. The same check ensures that `$D` is used in `pkg_preinst/pkg_postinst/pkg_prerm/pkg_postrm` functions instead of `${D}`.

- `S` now needs to be set to a valid value within a recipe. If `S` is not set in the recipe, the directory is not automatically created. If `S` does not point to a directory that exists at the time the `do_unpack` task finishes, a warning will be shown.

- `LICENSE` is now validated for correct formatting of multiple licenses. If the format is invalid (e.g. multiple licenses are specified with no operators to specify how the multiple licenses interact), then a warning will be shown.

### Miscellaneous Changes

The following miscellaneous changes have occurred:

- The `send-error-report` script now expects a "-s" option to be specified before the server address. This assumes a server address is being specified.

- The `oe-pkgdata-util` script now expects a "-p" option to be specified before the `pkgdata` directory, which is now optional. If the `pkgdata` directory is not specified, the script will run BitBake to query `PKGDATA_DIR` from the build environment.

## Moving to the Yocto Project 2.0 Release

This section provides migration information for moving to the Yocto Project 2.0 Release from the prior release.

### GCC 5

The default compiler is now GCC 5.2. This change has required fixes for compilation errors in a number of other recipes.

One important example is a fix for when the Linux kernel freezes at boot time on ARM when built with GCC 5. If you are using your own kernel recipe or source tree and building for ARM, you will likely need to apply this patch. The standard `linux-yocto` kernel source tree already has a workaround for the same issue.

For further details, see and the porting guide at .

Alternatively, you can switch back to GCC 4.9 or 4.8 by setting `GCCVERSION` in your configuration, as follows:

         GCCVERSION = "4.9%"

### Gstreamer 0.10 Removed

Gstreamer 0.10 has been removed in favor of Gstreamer 1.x. As part of the change, recipes for Gstreamer 0.10 and related software are now located in `meta-multimedia`. This change results in Qt4 having Phonon and Gstreamer support in QtWebkit disabled by default.

### Removed Recipes

The following recipes have been moved or removed:

- `bluez4`: The recipe is obsolete and has been moved due to `bluez5` becoming fully integrated. The `bluez4` recipe now resides in `meta-oe`.

- `gamin`: The recipe is obsolete and has been removed.

- `gnome-icon-theme`: The recipe's functionally has been replaced by `adwaita-icon-theme`.

- Gstreamer 0.10 Recipes: Recipes for Gstreamer 0.10 have been removed in favor of the recipes for Gstreamer 1.x.

- `insserv`: The recipe is obsolete and has been removed.

- `libunique`: The recipe is no longer used and has been moved to `meta-oe`.

- `midori`: The recipe's functionally has been replaced by `epiphany`.

- `python-gst`: The recipe is obsolete and has been removed since it only contains bindings for Gstreamer 0.10.

- `qt-mobility`: The recipe is obsolete and has been removed since it requires `Gstreamer 0.10`, which has been replaced.

- `subversion`: All 1.6.x versions of this recipe have been removed.

- `webkit-gtk`: The older 1.8.3 version of this recipe has been removed in favor of `webkitgtk`.

### BitBake datastore improvements

The method by which BitBake's datastore handles overrides has changed. Overrides are now applied dynamically and `bb.data.update_data()` is now a no-op. Thus, `bb.data.update_data()` is no longer required in order to apply the correct overrides. In practice, this change is unlikely to require any changes to Metadata. However, these minor changes in behavior exist:

- All potential overrides are now visible in the variable history as seen when you run the following:

           $ bitbake -e

- `d.delVar('`VARNAME`')` and `d.setVar('`VARNAME`', None)` result in the variable and all of its overrides being cleared out. Before the change, only the non-overridden values were cleared.

### Shell Message Function Changes

The shell versions of the BitBake message functions (i.e. `bbdebug`, `bbnote`, `bbwarn`, `bbplain`, `bberror`, and `bbfatal`) are now connected through to their BitBake equivalents `bb.debug()`, `bb.note()`, `bb.warn()`, `bb.plain()`, `bb.error()`, and `bb.fatal()`, respectively. Thus, those message functions that you would expect to be printed by the BitBake UI are now actually printed. In practice, this change means two things:

- If you now see messages on the console that you did not previously see as a result of this change, you might need to clean up the calls to `bbwarn`, `bberror`, and so forth. Or, you might want to simply remove the calls.

- The `bbfatal` message function now suppresses the full error log in the UI, which means any calls to `bbfatal` where you still wish to see the full error log should be replaced by `die` or `bbfatal_log`.

### Extra Development/Debug Package Cleanup

The following recipes have had extra `dev/dbg` packages removed:

- `acl`

- `apmd`

- `aspell`

- `attr`

- `augeas`

- `bzip2`

- `cogl`

- `curl`

- `elfutils`

- `gcc-target`

- `libgcc`

- `libtool`

- `libxmu`

- `opkg`

- `pciutils`

- `rpm`

- `sysfsutils`

- `tiff`

- `xz`

All of the above recipes now conform to the standard packaging scheme where a single `-dev`, `-dbg`, and `-staticdev` package exists per recipe.

### Recipe Maintenance Tracking Data Moved to OE-Core

Maintenance tracking data for recipes that was previously part of `meta-yocto` has been moved to OE-Core. The change includes `package_regex.inc` and `distro_alias.inc`, which are typically enabled when using the `distrodata` class. Additionally, the contents of `upstream_tracking.inc` has now been split out to the relevant recipes.

### Automatic Stale Sysroot File Cleanup

Stale files from recipes that no longer exist in the current configuration are now automatically removed from sysroot as well as removed from any other place managed by shared state. This automatic cleanup means that the build system now properly handles situations such as renaming the build system side of recipes, removal of layers from `bblayers.conf`, and `DISTRO_FEATURES` changes.

Additionally, work directories for old versions of recipes are now pruned. If you wish to disable pruning old work directories, you can set the following variable in your configuration:

         SSTATE_PRUNE_OBSOLETEWORKDIR = "0"

### `linux-yocto` Kernel Metadata Repository Now Split from Source

The `linux-yocto` tree has up to now been a combined set of kernel changes and configuration (meta) data carried in a single tree. While this format is effective at keeping kernel configuration and source modifications synchronized, it is not always obvious to developers how to manipulate the Metadata as compared to the source.

Metadata processing has now been removed from the `kernel-yocto` class and the external Metadata repository `yocto-kernel-cache`, which has always been used to seed the `linux-yocto` "meta" branch. This separate `linux-yocto` cache repository is now the primary location for this data. Due to this change, `linux-yocto` is no longer able to process combined trees. Thus, if you need to have your own combined kernel repository, you must do the split there as well and update your recipes accordingly. See the `meta/recipes-kernel/linux/linux-yocto_4.1.bb` recipe for an example.

### Additional QA checks

The following QA checks have been added:

- Added a "host-user-contaminated" check for ownership issues for packaged files outside of `/home`. The check looks for files that are incorrectly owned by the user that ran BitBake instead of owned by a valid user in the target system.

- Added an "invalid-chars" check for invalid (non-UTF8) characters in recipe metadata variable values (i.e. `DESCRIPTION`, `SUMMARY`, `LICENSE`, and `SECTION`). Some package managers do not support these characters.

- Added an "invalid-packageconfig" check for any options specified in `PACKAGECONFIG` that do not match any `PACKAGECONFIG` option defined for the recipe.

### Miscellaneous Changes

These additional changes exist:

- `gtk-update-icon-cache` has been renamed to `gtk-icon-utils`.

- The `tools-profile` `IMAGE_FEATURES` item as well as its corresponding packagegroup and `packagegroup-core-tools-profile` no longer bring in `oprofile`. Bringing in `oprofile` was originally added to aid compilation on resource-constrained targets. However, this aid has not been widely used and is not likely to be used going forward due to the more powerful target platforms and the existence of better cross-compilation tools.

- The `IMAGE_FSTYPES` variable's default value now specifies `ext4` instead of `ext3`.

- All support for the `PRINC` variable has been removed.

- The `packagegroup-core-full-cmdline` packagegroup no longer brings in `lighttpd` due to the fact that bringing in `lighttpd` is not really in line with the packagegroup's purpose, which is to add full versions of command-line tools that by default are provided by `busybox`.

## Moving to the Yocto Project 2.1 Release

This section provides migration information for moving to the Yocto Project 2.1 Release from the prior release.

### Variable Expansion in Python Functions

Variable expressions, such as `${`VARNAME`}` no longer expand automatically within Python functions. Suppressing expansion was done to allow Python functions to construct shell scripts or other code for situations in which you do not want such expressions expanded. For any existing code that relies on these expansions, you need to change the expansions to expand the value of individual variables through `d.getVar()`. To alternatively expand more complex expressions, use `d.expand()`.

### Overrides Must Now be Lower-Case

The convention for overrides has always been for them to be lower-case characters. This practice is now a requirement as BitBake's datastore now assumes lower-case characters in order to give a slight performance boost during parsing. In practical terms, this requirement means that anything that ends up in `OVERRIDES` must now appear in lower-case characters (e.g. values for `MACHINE`, `TARGET_ARCH`, `DISTRO`, and also recipe names if `_pn-`recipename overrides are to be effective).

### Expand Parameter to `getVar()` and `getVarFlag()` is Now Mandatory

The expand parameter to `getVar()` and `getVarFlag()` previously defaulted to False if not specified. Now, however, no default exists so one must be specified. You must change any `getVar()` calls that do not specify the final expand parameter to calls that do specify the parameter. You can run the following `sed` command at the base of a layer to make this change:

         sed -e 's:\(\.getVar([^,()]*\)):\1, False):g' -i `grep -ril getVar *`
         sed -e 's:\(\.getVarFlag([^,()]*, [^,()]*\)):\1, False):g' -i `grep -ril getVarFlag *`

The reason for this change is that it prepares the way for changing the default to True in a future Yocto Project release. This future change is a much more sensible default than False. However, the change needs to be made gradually as a sudden change of the default would potentially cause side-effects that would be difficult to detect.

### Makefile Environment Changes

`EXTRA_OEMAKE` now defaults to "" instead of "-e MAKEFLAGS=". Setting `EXTRA_OEMAKE` to "-e MAKEFLAGS=" by default was a historical accident that has required many classes (e.g. `autotools`, `module`) and recipes to override this default in order to work with sensible build systems. When upgrading to the release, you must edit any recipe that relies upon this old default by either setting `EXTRA_OEMAKE` back to "-e MAKEFLAGS=" or by explicitly setting any required variable value overrides using `EXTRA_OEMAKE`, which is typically only needed when a Makefile sets a default value for a variable that is inappropriate for cross-compilation using the "=" operator rather than the "?=" operator.

### `libexecdir` Reverted to `${prefix}/libexec`

The use of `${libdir}/${BPN}` as `libexecdir` is different as compared to all other mainstream distributions, which either uses `${prefix}/libexec` or `${libdir}`. The use is also contrary to the GNU Coding Standards (i.e. ) that suggest `${prefix}/libexec` and also notes that any package-specific nesting should be done by the package itself. Finally, having `libexecdir` change between recipes makes it very difficult for different recipes to invoke binaries that have been installed into `libexecdir`. The Filesystem Hierarchy Standard (i.e. ) now recognizes the use of `${prefix}/libexec/`, giving distributions the choice between `${prefix}/lib` or `${prefix}/libexec` without breaking FHS.

### `ac_cv_sizeof_off_t` is No Longer Cached in Site Files

For recipes inheriting the `autotools` class, `ac_cv_sizeof_off_t` is no longer cached in the site files for `autoconf`. The reason for this change is because the `ac_cv_sizeof_off_t` value is not necessarily static per architecture as was previously assumed. Rather, the value changes based on whether large file support is enabled. For most software that uses `autoconf`, this change should not be a problem. However, if you have a recipe that bypasses the standard `do_configure` task from the `autotools` class and the software the recipe is building uses a very old version of `autoconf`, the recipe might be incapable of determining the correct size of `off_t` during `do_configure`.

The best course of action is to patch the software as necessary to allow the default implementation from the `autotools` class to work such that `autoreconf` succeeds and produces a working configure script, and to remove the overridden `do_configure` task such that the default implementation does get used.

### Image Generation is Now Split Out from Filesystem Generation

Previously, for image recipes the `do_rootfs` task assembled the filesystem and then from that filesystem generated images. With this Yocto Project release, image generation is split into separate `do_image_*` tasks for clarity both in operation and in the code.

For most cases, this change does not present any problems. However, if you have made customizations that directly modify the `do_rootfs` task or that mention `do_rootfs`, you might need to update those changes. In particular, if you had added any tasks after `do_rootfs`, you should make edits so that those tasks are after the `do_image_complete` task rather than after `do_rootfs` so that the your added tasks run at the correct time.

A minor part of this restructuring is that the post-processing definitions and functions have been moved from the `image` class to the `rootfs-postcommands` class. Functionally, however, they remain unchanged.

### Removed Recipes

The following recipes have been removed in the 2.1 release:

- `gcc` version 4.8: Versions 4.9 and 5.3 remain.

- `qt4`: All support for Qt 4.x has been moved out to a separate `meta-qt4` layer because Qt 4 is no longer supported upstream.

- `x11vnc`: Moved to the `meta-oe` layer.

- `linux-yocto-3.14`: No longer supported.

- `linux-yocto-3.19`: No longer supported.

- `libjpeg`: Replaced by the `libjpeg-turbo` recipe.

- `pth`: Became obsolete.

- `liboil`: Recipe is no longer needed and has been moved to the `meta-multimedia` layer.

- `gtk-theme-torturer`: Recipe is no longer needed and has been moved to the `meta-gnome` layer.

- `gnome-mime-data`: Recipe is no longer needed and has been moved to the `meta-gnome` layer.

- `udev`: Replaced by the `eudev` recipe for compatibility when using `sysvinit` with newer kernels.

- `python-pygtk`: Recipe became obsolete.

- `adt-installer`: Recipe became obsolete. See the "ADT Removed" section for more information.

### Class Changes

The following classes have changed:

- `autotools_stage`: Removed because the `autotools` class now provides its functionality. Recipes that inherited from `autotools_stage` should now inherit from `autotools` instead.

- `boot-directdisk`: Merged into the `image-vm` class. The `boot-directdisk` class was rarely directly used. Consequently, this change should not cause any issues.

- `bootimg`: Merged into the `image-live` class. The `bootimg` class was rarely directly used. Consequently, this change should not cause any issues.

- `packageinfo`: Removed due to its limited use by the Hob UI, which has itself been removed.

### Build System User Interface Changes

The following changes have been made to the build system user interface:

- Hob GTK+-based UI: Removed because it is unmaintained and based on the outdated GTK+ 2 library. The Toaster web-based UI is much more capable and is actively maintained. See the "Using the Toaster Web Interface" section in the Toaster User Manual for more information on this interface.

- "puccho" BitBake UI: Removed because is unmaintained and no longer useful.

### ADT Removed

The Application Development Toolkit (ADT) has been removed because its functionality almost completely overlapped with the standard SDK and the extensible SDK. For information on these SDKs and how to build and use them, see the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

The Yocto Project Eclipse IDE Plug-in is still supported and is not affected by this change.

### Poky Reference Distribution Changes

The following changes have been made for the Poky distribution:

- The `meta-yocto` layer has been renamed to `meta-poky` to better match its purpose, which is to provide the Poky reference distribution. The `meta-yocto-bsp` layer retains its original name since it provides reference machines for the Yocto Project and it is otherwise unrelated to Poky. References to `meta-yocto` in your `conf/bblayers.conf` should automatically be updated, so you should not need to change anything unless you are relying on this naming elsewhere.

- The `uninative` class is now enabled by default in Poky. This class attempts to isolate the build system from the host distribution's C library and makes re-use of native shared state artifacts across different host distributions practical. With this class enabled, a tarball containing a pre-built C library is downloaded at the start of the build.

  The `uninative` class is enabled through the `meta/conf/distro/include/yocto-uninative.inc` file, which for those not using the Poky distribution, can include to easily enable the same functionality.

  Alternatively, if you wish to build your own `uninative` tarball, you can do so by building the `uninative-tarball` recipe, making it available to your build machines (e.g. over HTTP/HTTPS) and setting a similar configuration as the one set by `yocto-uninative.inc`.

- Static library generation, for most cases, is now disabled by default in the Poky distribution. Disabling this generation saves some build time as well as the size used for build output artifacts.

  Disabling this library generation is accomplished through a `meta/conf/distro/include/no-static-libs.inc`, which for those not using the Poky distribution can easily include to enable the same functionality.

  Any recipe that needs to opt-out of having the "--disable-static" option specified on the configure command line either because it is not a supported option for the configure script or because static libraries are needed should set the following variable:

           DISABLE_STATIC = ""

- The separate `poky-tiny` distribution now uses the musl C library instead of a heavily pared down `glibc`. Using musl results in a smaller distribution and facilitates much greater maintainability because musl is designed to have a small footprint.

  If you have used `poky-tiny` and have customized the `glibc` configuration you will need to redo those customizations with musl when upgrading to the new release.

### Packaging Changes

The following changes have been made to packaging:

- The `runuser` and `mountpoint` binaries, which were previously in the main `util-linux` package, have been split out into the `util-linux-runuser` and `util-linux-mountpoint` packages, respectively.

- The `python-elementtree` package has been merged into the `python-xml` package.

### Tuning File Changes

The following changes have been made to the tuning files:

- The "no-thumb-interwork" tuning feature has been dropped from the ARM tune include files. Because interworking is required for ARM EABI, attempting to disable it through a tuning feature no longer makes sense.

  Support for ARM OABI was deprecated in gcc 4.7.

- The `tune-cortexm*.inc` and `tune-cortexr4.inc` files have been removed because they are poorly tested. Until the OpenEmbedded build system officially gains support for CPUs without an MMU, these tuning files would probably be better maintained in a separate layer if needed.

### Supporting GObject Introspection

This release supports generation of GLib Introspective Repository (GIR) files through GObject introspection, which is the standard mechanism for accessing GObject-based software from runtime environments. You can enable, disable, and test the generation of this data. See the "Enabling GObject Introspection Support" section in the Yocto Project Development Tasks Manual for more information.

### Miscellaneous Changes

These additional changes exist:

- The minimum Git version has been increased to 1.8.3.1. If your host distribution does not provide a sufficiently recent version, you can install the buildtools, which will provide it. See the "Required Git, tar, Python and gcc Versions" section for more information on the buildtools tarball.

- The buggy and incomplete support for the RPM version 4 package manager has been removed. The well-tested and maintained support for RPM version 5 remains.

- Previously, the following list of packages were removed if package-management was not in `IMAGE_FEATURES`, regardless of any dependencies:

           update-rc.d
           base-passwd
           shadow
           update-alternatives
           run-postinsts

  With the Yocto Project 2.1 release, these packages are only removed if "read-only-rootfs" is in `IMAGE_FEATURES`, since they might still be needed for a read-write image even in the absence of a package manager (e.g. if users need to be added, modified, or removed at runtime).

- The `devtool modify` command now defaults to extracting the source since that is most commonly expected. The "-x" or "--extract" options are now no-ops. If you wish to provide your own existing source tree, you will now need to specify either the "-n" or "--no-extract" options when running `devtool modify`.

- If the formfactor for a machine is either not supplied or does not specify whether a keyboard is attached, then the default is to assume a keyboard is attached rather than assume no keyboard. This change primarily affects the Sato UI.

- The `.debug` directory packaging is now automatic. If your recipe builds software that installs binaries into directories other than the standard ones, you no longer need to take care of setting `FILES_${PN}-dbg` to pick up the resulting `.debug` directories as these directories are automatically found and added.

- Inaccurate disk and CPU percentage data has been dropped from `buildstats` output. This data has been replaced with `getrusage()` data and corrected IO statistics. You will probably need to update any custom code that reads the `buildstats` data.

- The `meta/conf/distro/include/package_regex.inc` is now deprecated. The contents of this file have been moved to individual recipes.

  Tip

  Because this file will likely be removed in a future Yocto Project release, it is suggested that you remove any references to the file that might be in your configuration.

- The `v86d/uvesafb` has been removed from the `genericx86` and `genericx86-64` reference machines, which are provided by the `meta-yocto-bsp` layer. Most modern x86 boards do not rely on this file and it only adds kernel error messages during startup. If you do still need to support `uvesafb`, you can simply add `v86d` to your image.

- Build sysroot paths are now removed from debug symbol files. Removing these paths means that remote GDB using an unstripped build system sysroot will no longer work (although this was never documented to work). The supported method to accomplish something similar is to set `IMAGE_GEN_DEBUGFS` to "1", which will generate a companion debug image containing unstripped binaries and associated debug sources alongside the image.

## Moving to the Yocto Project 2.2 Release

This section provides migration information for moving to the Yocto Project 2.2 Release from the prior release.

### Minimum Kernel Version

The minimum kernel version for the target system and for SDK is now 3.2.0, due to the upgrade to `glibc 2.24`. Specifically, for AArch64-based targets the version is 3.14. For Nios II-based targets, the minimum kernel version is 3.19.

For x86 and x86_64, you can reset `OLDEST_KERNEL` to anything down to 2.6.32 if desired.

### Staging Directories in Sysroot Has Been Simplified

The way directories are staged in sysroot has been simplified and introduces the new `SYSROOT_DIRS`, `SYSROOT_DIRS_NATIVE`, and `SYSROOT_DIRS_BLACKLIST`. See the v2 patch series on the OE-Core Mailing List for additional information.

### Removal of Old Images and Other Files in `tmp/deploy` Now Enabled

Removal of old images and other files in `tmp/deploy/` is now enabled by default due to a new staging method used for those files. As a result of this change, the `RM_OLD_IMAGE` variable is now redundant.

### Python Changes

The following changes for Python occurred:

#### BitBake Now Requires Python 3.4+

BitBake requires Python 3.4 or greater.

#### UTF-8 Locale Required on Build Host

A UTF-8 locale is required on the build host due to Python 3. Since C.UTF-8 is not a standard, the default is en_US.UTF-8.

#### Metadata Must Now Use Python 3 Syntax

The metadata is now required to use Python 3 syntax. For help preparing metadata, see any of the many Python 3 porting guides available. Alternatively, you can reference the conversion commits for Bitbake and you can use OE-Core as a guide for changes. Following are particular areas of interest:

         * subprocess command-line pipes needing locale decoding
         * the syntax for octal values changed
         * the iter*() functions changed name
         * iterators now return views, not lists
         * changed names for Python modules

#### Target Python Recipes Switched to Python 3

Most target Python recipes have now been switched to Python 3. Unfortunately, systems using RPM as a package manager and providing online package-manager support through SMART still require Python 2.

Python 2 and recipes that use it can still be built for the target as with previous versions.

#### `buildtools-tarball` Includes Python 3

`buildtools-tarball` now includes Python 3.

### uClibc Replaced by musl

uClibc has been removed in favor of musl. Musl has matured, is better maintained, and is compatible with a wider range of applications as compared to uClibc.

### `${B}` No Longer Default Working Directory for Tasks

`${``B``}` is no longer the default working directory for tasks. Consequently, any custom tasks you define now need to either have the `[``dirs``]` flag set, or the task needs to change into the appropriate working directory manually (e.g using `cd` for a shell task).

The preferred method is to use the `[dirs]` flag.

### `runqemu` Ported to Python

`runqemu` has been ported to Python and has changed behavior in some cases. Previous usage patterns continue to be supported.

The new `runqemu` is a Python script. Machine knowledge is no longer hardcoded into `runqemu`. You can choose to use the `qemuboot` configuration file to define the BSP's own arguments and to make it bootable with `runqemu`. If you use a configuration file, use the following form:

         image-name-machine.qemuboot.conf

The configuration file enables fine-grained tuning of options passed to QEMU without the `runqemu` script hard-coding any knowledge about different machines. Using a configuration file is particularly convenient when trying to use QEMU with machines other than the `qemu*` machines in OE-Core. The `qemuboot.conf` file is generated by the `qemuboot` class when the root filesystem is being build (i.e. build rootfs). QEMU boot arguments can be set in BSP's configuration file and the `qemuboot` class will save them to `qemuboot.conf`.

If you want to use `runqemu` without a configuration file, use the following command form:

         $ runqemu machine rootfs kernel [options]

Supported machines are as follows:

         qemuarm
         qemuarm64
         qemux86
         qemux86-64
         qemuppc
         qemumips
         qemumips64
         qemumipsel
         qemumips64el

Consider the following example, which uses the `qemux86-64` machine, provides a root filesystem, provides an image, and uses the `nographic` option:

    $ runqemu qemux86-64 tmp/deploy/images/qemux86-64/core-image-minimal-qemux86-64.ext4 tmp/deploy/images/qemux86-64/bzImage nographic

Following is a list of variables that can be set in configuration files such as `bsp.conf` to enable the BSP to be booted by `runqemu`:

"QB" means "QEMU Boot".

         QB_SYSTEM_NAME: QEMU name (e.g. "qemu-system-i386")
         QB_OPT_APPEND: Options to append to QEMU (e.g. "-show-cursor")
         QB_DEFAULT_KERNEL: Default kernel to boot (e.g. "bzImage")
         QB_DEFAULT_FSTYPE: Default FSTYPE to boot (e.g. "ext4")
         QB_MEM: Memory (e.g. "-m 512")
         QB_MACHINE: QEMU machine (e.g. "-machine virt")
         QB_CPU: QEMU cpu (e.g. "-cpu qemu32")
         QB_CPU_KVM: Similar to QB_CPU except used for kvm support (e.g. "-cpu kvm64")
         QB_KERNEL_CMDLINE_APPEND: Options to append to the kernel's -append
                                   option (e.g. "console=ttyS0 console=tty")
         QB_DTB: QEMU dtb name
         QB_AUDIO_DRV: QEMU audio driver (e.g. "alsa", set it when support audio)
         QB_AUDIO_OPT: QEMU audio option (e.g. "-soundhw ac97,es1370"), which is used
                       when QB_AUDIO_DRV is set.
         QB_KERNEL_ROOT: Kernel's root (e.g. /dev/vda)
         QB_TAP_OPT: Network option for 'tap' mode (e.g.
                     "-netdev tap,id=net0,ifname=@TAP@,script=no,downscript=no -device virtio-net-device,netdev=net0").
                      runqemu will replace "@TAP@" with the one that is used, such as tap0, tap1 ...
         QB_SLIRP_OPT: Network option for SLIRP mode (e.g. "-netdev user,id=net0 -device virtio-net-device,netdev=net0")
         QB_ROOTFS_OPT: Used as rootfs (e.g.
                        "-drive id=disk0,file=@ROOTFS@,if=none,format=raw -device virtio-blk-device,drive=disk0").
                        runqemu will replace "@ROOTFS@" with the one which is used, such as
                        core-image-minimal-qemuarm64.ext4.
         QB_SERIAL_OPT: Serial port (e.g. "-serial mon:stdio")
         QB_TCPSERIAL_OPT: tcp serial port option (e.g.
                           " -device virtio-serial-device -chardev socket,id=virtcon,port=@PORT@,host=127.0.0.1 -device      virtconsole,chardev=virtcon"
                           runqemu will replace "@PORT@" with the port number which is used.

To use `runqemu`, set `IMAGE_CLASSES` as follows and run `runqemu`:

For command-line syntax, use `runqemu help`.

         IMAGE_CLASSES += "qemuboot"

### Default Linker Hash Style Changed

The default linker hash style for `gcc-cross` is now "sysv" in order to catch recipes that are building software without using the OpenEmbedded `LDFLAGS`. This change could result in seeing some "No GNU_HASH in the elf binary" QA issues when building such recipes. You need to fix these recipes so that they use the expected `LDFLAGS`. Depending on how the software is built, the build system used by the software (e.g. a Makefile) might need to be patched. However, sometimes making this fix is as simple as adding the following to the recipe:

         TARGET_CC_ARCH += "${LDFLAGS}"

### `KERNEL_IMAGE_BASE_NAME` no Longer Uses `KERNEL_IMAGETYPE`

The `KERNEL_IMAGE_BASE_NAME` variable no longer uses the `KERNEL_IMAGETYPE` variable to create the image's base name. Because the OpenEmbedded build system can now build multiple kernel image types, this part of the kernel image base name as been removed leaving only the following:

         KERNEL_IMAGE_BASE_NAME ?= "${PKGE}-${PKGV}-${PKGR}-${MACHINE}-${DATETIME}"

If you have recipes or classes that use `KERNEL_IMAGE_BASE_NAME` directly, you might need to update the references to ensure they continue to work.

### BitBake Changes

The following changes took place for BitBake:

- The "goggle" UI and standalone image-writer tool have been removed as they both require GTK+ 2.0 and were not being maintained.

- The Perforce fetcher now supports `SRCREV` for specifying the source revision to use, be it `${``AUTOREV``}`, changelist number, p4date, or label, in preference to separate `SRC_URI` parameters to specify these. This change is more in-line with how the other fetchers work for source control systems. Recipes that fetch from Perforce will need to be updated to use `SRCREV` in place of specifying the source revision within `SRC_URI`.

- Some of BitBake's internal code structures for accessing the recipe cache needed to be changed to support the new multi-configuration functionality. These changes will affect external tools that use BitBake's tinfoil module. For information on these changes, see the changes made to the scripts supplied with OpenEmbedded-Core: 1 and 2.

- The task management code has been rewritten to avoid using ID indirection in order to improve performance. This change is unlikely to cause any problems for most users. However, the setscene verification function as pointed to by `BB_SETSCENE_VERIFY_FUNCTION` needed to change signature. Consequently, a new variable named `BB_SETSCENE_VERIFY_FUNCTION2` has been added allowing multiple versions of BitBake to work with suitably written metadata, which includes OpenEmbedded-Core and Poky. Anyone with custom BitBake task scheduler code might also need to update the code to handle the new structure.

### Swabber has Been Removed

Swabber, a tool that was intended to detect host contamination in the build process, has been removed, as it has been unmaintained and unused for some time and was never particularly effective. The OpenEmbedded build system has since incorporated a number of mechanisms including enhanced QA checks that mean that there is less of a need for such a tool.

### Removed Recipes

The following recipes have been removed:

- `augeas`: No longer needed and has been moved to `meta-oe`.

- `directfb`: Unmaintained and has been moved to `meta-oe`.

- `gcc`: Removed 4.9 version. Versions 5.4 and 6.2 are still present.

- `gnome-doc-utils`: No longer needed.

- `gtk-doc-stub`: Replaced by `gtk-doc`.

- `gtk-engines`: No longer needed and has been moved to `meta-gnome`.

- `gtk-sato-engine`: Became obsolete.

- `libglade`: No longer needed and has been moved to `meta-oe`.

- `libmad`: Unmaintained and functionally replaced by `libmpg123`. `libmad` has been moved to `meta-oe`.

- `libowl`: Became obsolete.

- `libxsettings-client`: No longer needed.

- `oh-puzzles`: Functionally replaced by `puzzles`.

- `oprofileui`: Became obsolete. OProfile has been largely supplanted by perf.

- `packagegroup-core-directfb.bb`: Removed.

- `core-image-directfb.bb`: Removed.

- `pointercal`: No longer needed and has been moved to `meta-oe`.

- `python-imaging`: No longer needed and moved to `meta-python`

- `python-pyrex`: No longer needed and moved to `meta-python`.

- `sato-icon-theme`: Became obsolete.

- `swabber-native`: Swabber has been removed. See the entry on Swabber.

- `tslib`: No longer needed and has been moved to `meta-oe`.

- `uclibc`: Removed in favor of musl.

- `xtscal`: No longer needed and moved to `meta-oe`

### Removed Classes

The following classes have been removed:

- `distutils-native-base`: No longer needed.

- `distutils3-native-base`: No longer needed.

- `sdl`: Only set `DEPENDS` and `SECTION`, which are better set within the recipe instead.

- `sip`: Mostly unused.

- `swabber`: See the entry on Swabber.

### Minor Packaging Changes

The following minor packaging changes have occurred:

- `grub`: Split `grub-editenv` into its own package.

- `systemd`: Split container and vm related units into a new package, systemd-container.

- `util-linux`: Moved `prlimit` to a separate `util-linux-prlimit` package.

### Miscellaneous Changes

The following miscellaneous changes have occurred:

- `package_regex.inc`: Removed because the definitions `package_regex.inc` previously contained have been moved to their respective recipes.

- Both `devtool add` and `recipetool create` now use a fixed `SRCREV` by default when fetching from a Git repository. You can override this in either case to use `${``AUTOREV``}` instead by using the `-a` or `‐‐autorev` command-line option

- `distcc`: GTK+ UI is now disabled by default.

- `packagegroup-core-tools-testapps`: Removed Piglit.

- `image.bbclass`: Renamed COMPRESS(ION) to CONVERSION. This change means that `COMPRESSIONTYPES`, `COMPRESS_DEPENDS` and `COMPRESS_CMD` are deprecated in favor of `CONVERSIONTYPES`, `CONVERSION_DEPENDS` and `CONVERSION_CMD`. The `COMPRESS*` variable names will still work in the 2.2 release but metadata that does not need to be backwards-compatible should be changed to use the new names as the `COMPRESS*` ones will be removed in a future release.

- `gtk-doc`: A full version of `gtk-doc` is now made available. However, some old software might not be capable of using the current version of `gtk-doc` to build documentation. You need to change recipes that build such software so that they explicitly disable building documentation with `gtk-doc`.

## Moving to the Yocto Project 2.3 Release

This section provides migration information for moving to the Yocto Project 2.3 Release from the prior release.

### Recipe-specific Sysroots

The OpenEmbedded build system now uses one sysroot per recipe to resolve long-standing issues with configuration script auto-detection of undeclared dependencies. Consequently, you might find that some of your previously written custom recipes are missing declared dependencies, particularly those dependencies that are incidentally built earlier in a typical build process and thus are already likely to be present in the shared sysroot in previous releases.

Consider the following:

- Declare Build-Time Dependencies: Because of this new feature, you must explicitly declare all build-time dependencies for your recipe. If you do not declare these dependencies, they are not populated into the sysroot for the recipe.

- Specify Pre-Installation and Post-Installation Native Tool Dependencies: You must specifically specify any special native tool dependencies of `pkg_preinst` and `pkg_postinst` scripts by using the `PACKAGE_WRITE_DEPS` variable. Specifying these dependencies ensures that these tools are available if these scripts need to be run on the build host during the `do_rootfs` task.

  As an example, see the `dbus` recipe. You will see that this recipe has a `pkg_postinst` that calls `systemctl` if "systemd" is in `DISTRO_FEATURES`. In the example, `systemd-systemctl-native` is added to `PACKAGE_WRITE_DEPS`, which is also conditional on "systemd" being in `DISTRO_FEATURES`.

- Examine Recipes that Use `SSTATEPOSTINSTFUNCS`: You need to examine any recipe that uses `SSTATEPOSTINSTFUNCS` and determine steps to take.

  Functions added to `SSTATEPOSTINSTFUNCS` are still called as they were in previous Yocto Project releases. However, since a separate sysroot is now being populated for every recipe and if existing functions being called through `SSTATEPOSTINSTFUNCS` are doing relocation, then you will need to change these to use a post-installation script that is installed by a function added to `SYSROOT_PREPROCESS_FUNCS`.

  For an example, see the `pixbufcache` class in `meta/classes/` in the Yocto Project Source Repositories.

  The `SSTATEPOSTINSTFUNCS` variable itself is now deprecated in favor of the `do_populate_sysroot[postfuncs]` task. Consequently, if you do still have any function or functions that need to be called after the sysroot component is created for a recipe, then you would be well advised to take steps to use a post installation script as described previously. Taking these steps prepares your code for when `SSTATEPOSTINSTFUNCS` is removed in a future Yocto Project release.

- Specify the Sysroot when Using Certain External Scripts: Because the shared sysroot is now gone, the scripts `oe-find-native-sysroot` and `oe-run-native` have been changed such that you need to specify which recipe's `STAGING_DIR_NATIVE` is used.

You can find more information on how recipe-specific sysroots work in the "`staging.bbclass`" section.

### `PATH` Variable

Within the environment used to run build tasks, the environment variable `PATH` is now sanitized such that the normal native binary paths (`/bin`, `/sbin`, `/usr/bin` and so forth) are removed and a directory containing symbolic links linking only to the binaries from the host mentioned in the `HOSTTOOLS` and `HOSTTOOLS_NONFATAL` variables is added to `PATH`.

Consequently, any native binaries provided by the host that you need to call needs to be in one of these two variables at the configuration level.

Alternatively, you can add a native recipe (i.e. `-native`) that provides the binary to the recipe's `DEPENDS` value.

`PATH` is not sanitized in the same way within `devshell`. If it were, you would have difficulty running host tools for development and debugging within the shell.

### Changes to Scripts

The following changes to scripts took place:

- `oe-find-native-sysroot`: The usage for the `oe-find-native-sysroot` script has changed to the following:

           $ . oe-find-native-sysroot recipe

  You must now supply a recipe for recipe as part of the command. Prior to the Yocto Project &DISTRO; release, it was not necessary to provide the script with the command.

- `oe-run-native`: The usage for the `oe-run-native` script has changed to the following:

           $ oe-run-native native_recipe tool

  You must supply the name of the native recipe and the tool you want to run as part of the command. Prior to the Yocto Project &DISTRO; release, it was not necessary to provide the native recipe with the command.

- `cleanup-workdir`: The `cleanup-workdir` script has been removed because the script was found to be deleting files it should not have, which lead to broken build trees. Rather than trying to delete portions of `TMPDIR` and getting it wrong, it is recommended that you delete `TMPDIR` and have it restored from shared state (sstate) on subsequent builds.

- `wipe-sysroot`: The `wipe-sysroot` script has been removed as it is no longer needed with recipe-specific sysroots.

### Changes to Functions

The previously deprecated `bb.data.getVar()`, `bb.data.setVar()`, and related functions have been removed in favor of `d.getVar()`, `d.setVar()`, and so forth.

You need to fix any references to these old functions.

### BitBake Changes

The following changes took place for BitBake:

- BitBake's Graphical Dependency Explorer UI Replaced: BitBake's graphical dependency explorer UI `depexp` was replaced by `taskexp` ("Task Explorer"), which provides a graphical way of exploring the `task-depends.dot` file. The data presented by Task Explorer is much more accurate than the data that was presented by `depexp`. Being able to visualize the data is an often requested feature as standard `*.dot` file viewers cannot usual cope with the size of the `task-depends.dot` file.

- BitBake "-g" Output Changes: The `package-depends.dot` and `pn-depends.dot` files as previously generated using the `bitbake -g` command have been removed. A `recipe-depends.dot` file is now generated as a collapsed version of `task-depends.dot` instead.

  The reason for this change is because `package-depends.dot` and `pn-depends.dot` largely date back to a time before task-based execution and do not take into account task-level dependencies between recipes, which could be misleading.

- Mirror Variable Splitting Changes: Mirror variables including `MIRRORS`, `PREMIRRORS`, and `SSTATE_MIRRORS` can now separate values entirely with spaces. Consequently, you no longer need "\\n". BitBake looks for pairs of values, which simplifies usage. There should be no change required to existing mirror variable values themselves.

- The Subversion (SVN) Fetcher Uses an "ssh" Parameter and Not an "rsh" Parameter: The SVN fetcher now takes an "ssh" parameter instead of an "rsh" parameter. This new optional parameter is used when the "protocol" parameter is set to "svn+ssh". You can only use the new parameter to specify the `ssh` program used by SVN. The SVN fetcher passes the new parameter through the `SVN_SSH` environment variable during the `do_fetch` task.

  See the "Subversion (SVN) Fetcher (svn://)" section in the BitBake User Manual for additional information.

- `BB_SETSCENE_VERIFY_FUNCTION` and `BB_SETSCENE_VERIFY_FUNCTION2` Removed: Because the mechanism they were part of is no longer necessary with recipe-specific sysroots, the `BB_SETSCENE_VERIFY_FUNCTION` and `BB_SETSCENE_VERIFY_FUNCTION2` variables have been removed.

### Absolute Symbolic Links

Absolute symbolic links (symlinks) within staged files are no longer permitted and now trigger an error. Any explicit creation of symlinks can use the `lnr` script, which is a replacement for `ln -r`.

If the build scripts in the software that the recipe is building are creating a number of absolute symlinks that need to be corrected, you can inherit `relative_symlinks` within the recipe to turn those absolute symlinks into relative symlinks.

### GPLv2 Versions of GPLv3 Recipes Moved

Older GPLv2 versions of GPLv3 recipes have moved to a separate `meta-gplv2` layer.

If you use `INCOMPATIBLE_LICENSE` to exclude GPLv3 or set `PREFERRED_VERSION` to substitute a GPLv2 version of a GPLv3 recipe, then you must add the `meta-gplv2` layer to your configuration.

You can find `meta-gplv2` layer in the OpenEmbedded layer index at .

These relocated GPLv2 recipes do not receive the same level of maintenance as other core recipes. The recipes do not get security fixes and upstream no longer maintains them. In fact, the upstream community is actively hostile towards people that use the old versions of the recipes. Moving these recipes into a separate layer both makes the different needs of the recipes clearer and clearly identifies the number of these recipes.

The long-term solution might be to move to BSD-licensed replacements of the GPLv3 components for those that need to exclude GPLv3-licensed components from the target system. This solution will be investigated for future Yocto Project releases.

### Package Management Changes

The following package management changes took place:

- Smart package manager is replaced by DNF package manager. Smart has become unmaintained upstream, is not ported to Python 3.x. Consequently, Smart needed to be replaced. DNF is the only feasible candidate.

  The change in functionality is that the on-target runtime package management from remote package feeds is now done with a different tool that has a different set of command-line options. If you have scripts that call the tool directly, or use its API, they need to be fixed.

  For more information, see the DNF Documentation.

- Rpm 5.x is replaced with Rpm 4.x. This is done for two major reasons:

  - DNF is API-incompatible with Rpm 5.x and porting it and maintaining the port is non-trivial.

  - Rpm 5.x itself has limited maintenance upstream, and the Yocto Project is one of the very few remaining users.

- Berkeley DB 6.x is removed and Berkeley DB 5.x becomes the default:

  - Version 6.x of Berkeley DB has largely been rejected by the open source community due to its AGPLv3 license. As a result, most mainstream open source projects that require DB are still developed and tested with DB 5.x.

  - In OE-core, the only thing that was requiring DB 6.x was Rpm 5.x. Thus, no reason exists to continue carrying DB 6.x in OE-core.

- `createrepo` is replaced with `createrepo_c`.

  `createrepo_c` is the current incarnation of the tool that generates remote repository metadata. It is written in C as compared to `createrepo`, which is written in Python. `createrepo_c` is faster and is maintained.

- Architecture-independent RPM packages are "noarch" instead of "all".

  This change was made because too many places in DNF/RPM4 stack already make that assumption. Only the filenames and the architecture tag has changed. Nothing else has changed in OE-core system, particularly in the `allarch.bbclass` class.

- Signing of remote package feeds using `PACKAGE_FEED_SIGN` is not currently supported. This issue will be fully addressed in a future Yocto Project release. See defect 11209 for more information on a solution to package feed signing with RPM in the Yocto Project 2.3 release.

- OPKG now uses the libsolv backend for resolving package dependencies by default. This is vastly superior to OPKG's internal ad-hoc solver that was previously used. This change does have a small impact on disk (around 500 KB) and memory footprint.

  For further details on this change, see the commit message.

### Removed Recipes

The following recipes have been removed:

- `linux-yocto 4.8:` Version 4.8 has been removed. Versions 4.1 (LTSI), 4.4 (LTS), 4.9 (LTS/LTSI) and 4.10 are now present.

- `python-smartpm:` Functionally replaced by `dnf`.

- `createrepo:` Replaced by the `createrepo-c` recipe.

- `rpmresolve:` No longer needed with the move to RPM 4 as RPM itself is used instead.

- `gstreamer:` Removed the GStreamer Git version recipes as they have been stale. `1.10.`x recipes are still present.

- `alsa-conf-base:` Merged into `alsa-conf` since `libasound` depended on both. Essentially, no way existed to install only one of these.

- `tremor:` Moved to `meta-multimedia`. Fixed-integer Vorbis decoding is not needed by current hardware. Thus, GStreamer's ivorbis plugin has been disabled by default eliminating the need for the `tremor` recipe in OE-Core.

- `gummiboot:` Replaced by `systemd-boot`.

### Wic Changes

The following changes have been made to Wic:

For more information on Wic, see the "Creating Partitioned Images Using Wic" section in the Yocto Project Development Tasks Manual.

- Default Output Directory Changed: Wic's default output directory is now the current directory by default instead of the unusual `/var/tmp/wic`.

  The "-o" and "--outdir" options remain unchanged and are used to specify your preferred output directory if you do not want to use the default directory.

- fsimage Plug-in Removed: The Wic fsimage plugin has been removed as it duplicates functionality of the rawcopy plugin.

### QA Changes

The following QA checks have changed:

- `unsafe-references-in-binaries`: The `unsafe-references-in-binaries` QA check, which was disabled by default, has now been removed. This check was intended to detect binaries in `/bin` that link to libraries in `/usr/lib` and have the case where the user has `/usr` on a separate filesystem to `/`.

  The removed QA check was buggy. Additionally, `/usr` residing on a separate partition from `/` is now a rare configuration. Consequently, `unsafe-references-in-binaries` was removed.

- `file-rdeps`: The `file-rdeps` QA check is now an error by default instead of a warning. Because it is an error instead of a warning, you need to address missing runtime dependencies.

  For additional information, see the `insane` class and the "Errors and Warnings" section.

### Miscellaneous Changes

The following miscellaneous changes have occurred:

- In this release, a number of recipes have been changed to ignore the `largefile` `DISTRO_FEATURES` item, enabling large file support unconditionally. This feature has always been enabled by default. Disabling the feature has not been widely tested.

  Future releases of the Yocto Project will remove entirely the ability to disable the `largefile` feature, which would make it unconditionally enabled everywhere.

- If the `DISTRO_VERSION` value contains the value of the `DATE` variable, which is the default between Poky releases, the `DATE` value is explicitly excluded from `/etc/issue` and `/etc/issue.net`, which is displayed at the login prompt, in order to avoid conflicts with Multilib enabled. Regardless, the `DATE` value is inaccurate if the `base-files` recipe is restored from shared state (sstate) rather than rebuilt.

  If you need the build date recorded in `/etc/issue*` or anywhere else in your image, a better method is to define a post-processing function to do it and have the function called from `ROOTFS_POSTPROCESS_COMMAND`. Doing so ensures the value is always up-to-date with the created image.

- Dropbear's `init` script now disables DSA host keys by default. This change is in line with the systemd service file, which supports RSA keys only, and with recent versions of OpenSSH, which deprecates DSA host keys.

- The `buildhistory` class now correctly uses tabs as separators between all columns in `installed-package-sizes.txt` in order to aid import into other tools.

- The `USE_LDCONFIG` variable has been replaced with the "ldconfig" `DISTRO_FEATURES` feature. Distributions that previously set:

           USE_LDCONFIG = "0"

  should now instead use the following:

           DISTRO_FEATURES_BACKFILL_CONSIDERED_append = " ldconfig"

- The default value of `COPYLEFT_LICENSE_INCLUDE` now includes all versions of AGPL licenses in addition to GPL and LGPL.

  The default list is not intended to be guaranteed as a complete safe list. You should seek legal advice based on what you are distributing if you are unsure.

- Kernel module packages are now suffixed with the kernel version in order to allow module packages from multiple kernel versions to co-exist on a target system. If you wish to return to the previous naming scheme that does not include the version suffix, use the following:

           KERNEL_MODULE_PACKAGE_SUFFIX to ""

- Removal of `libtool` `*.la` files is now enabled by default. The `*.la` files are not actually needed on Linux and relocating them is an unnecessary burden.

  If you need to preserve these `.la` files (e.g. in a custom distribution), you must change `INHERIT_DISTRO` such that "remove-libtool" is not included in the value.

- Extensible SDKs built for GCC 5+ now refuse to install on a distribution where the host GCC version is 4.8 or 4.9. This change resulted from the fact that the installation is known to fail due to the way the `uninative` shared state (sstate) package is built. See the `uninative` class for additional information.

- All native and nativesdk recipes now use a separate `DISTRO_FEATURES` value instead of sharing the value used by recipes for the target, in order to avoid unnecessary rebuilds.

  The `DISTRO_FEATURES` for `native` recipes is `DISTRO_FEATURES_NATIVE` added to an intersection of `DISTRO_FEATURES` and `DISTRO_FEATURES_FILTER_NATIVE`.

  For nativesdk recipes, the corresponding variables are `DISTRO_FEATURES_NATIVESDK` and `DISTRO_FEATURES_FILTER_NATIVESDK`.

- The `FILESDIR` variable, which was previously deprecated and rarely used, has now been removed. You should change any recipes that set `FILESDIR` to set `FILESPATH` instead.

- The `MULTIMACH_HOST_SYS` variable has been removed as it is no longer needed with recipe-specific sysroots.

## Moving to the Yocto Project 2.4 Release

This section provides migration information for moving to the Yocto Project 2.4 Release from the prior release.

### Memory Resident Mode

A persistent mode is now available in BitBake's default operation, replacing its previous "memory resident mode" (i.e. `oe-init-build-env-memres`). Now you only need to set `BB_SERVER_TIMEOUT` to a timeout (in seconds) and BitBake's server stays resident for that amount of time between invocations. The `oe-init-build-env-memres` script has been removed since a separate environment setup script is no longer needed.

### Packaging Changes

This section provides information about packaging changes that have occurred:

- `python3` Changes:

  - The main "python3" package now brings in all of the standard Python 3 distribution rather than a subset. This behavior matches what is expected based on traditional Linux distributions. If you wish to install a subset of Python 3, specify `python-core` plus one or more of the individual packages that are still produced.

  - `python3`: The `bz2.py`, `lzma.py`, and `_compression.py` scripts have been moved from the `python3-misc` package to the `python3-compression` package.

- `binutils`: The `libbfd` library is now packaged in a separate "libbfd" package. This packaging saves space when certain tools (e.g. `perf`) are installed. In such cases, the tools only need `libbfd` rather than all the packages in `binutils`.

- `util-linux` Changes:

  - The `su` program is now packaged in a separate "util-linux-su" package, which is only built when "pam" is listed in the `DISTRO_FEATURES` variable. `util-linux` should not be installed unless it is needed because `su` is normally provided through the shadow file format. The main `util-linux` package has runtime dependencies (i.e. `RDEPENDS`) on the `util-linux-su` package when "pam" is in `DISTRO_FEATURES`.

  - The `switch_root` program is now packaged in a separate "util-linux-switch-root" package for small initramfs images that do not need the whole `util-linux` package or the busybox binary, which are both much larger than `switch_root`. The main `util-linux` package has a recommended runtime dependency (i.e. `RRECOMMENDS`) on the `util-linux-switch-root` package.

  - The `ionice` program is now packaged in a separate "util-linux-ionice" package. The main `util-linux` package has a recommended runtime dependency (i.e. `RRECOMMENDS`) on the `util-linux-ionice` package.

- `initscripts`: The `sushell` program is now packaged in a separate "initscripts-sushell" package. This packaging change allows systems to pull `sushell` in when `selinux` is enabled. The change also eliminates needing to pull in the entire `initscripts` package. The main `initscripts` package has a runtime dependency (i.e. `RDEPENDS`) on the `sushell` package when "selinux" is in `DISTRO_FEATURES`.

- `glib-2.0`: The `glib-2.0` package now has a recommended runtime dependency (i.e. `RRECOMMENDS`) on the `shared-mime-info` package, since large portions of GIO are not useful without the MIME database. You can remove the dependency by using the `BAD_RECOMMENDATIONS` variable if `shared-mime-info` is too large and is not required.

- Go Standard Runtime: The Go standard runtime has been split out from the main `go` recipe into a separate `go-runtime` recipe.

### Removed Recipes

The following recipes have been removed:

- `acpitests`: This recipe is not maintained.

- `autogen-native`: No longer required by Grub, oe-core, or meta-oe.

- `bdwgc`: Nothing in OpenEmbedded-Core requires this recipe. It has moved to meta-oe.

- `byacc`: This recipe was only needed by rpm 5.x and has moved to meta-oe.

- `gcc (5.4)`: The 5.4 series dropped the recipe in favor of 6.3 / 7.2.

- `gnome-common`: Deprecated upstream and no longer needed.

- `go-bootstrap-native`: Go 1.9 does its own bootstrapping so this recipe has been removed.

- `guile`: This recipe was only needed by `autogen-native` and `remake`. The recipe is no longer needed by either of these programs.

- `libclass-isa-perl`: This recipe was previously needed for LSB 4, no longer needed.

- `libdumpvalue-perl`: This recipe was previously needed for LSB 4, no longer needed.

- `libenv-perl`: This recipe was previously needed for LSB 4, no longer needed.

- `libfile-checktree-perl`: This recipe was previously needed for LSB 4, no longer needed.

- `libi18n-collate-perl`: This recipe was previously needed for LSB 4, no longer needed.

- `libiconv`: This recipe was only needed for `uclibc`, which was removed in the previous release. `glibc` and `musl` have their own implementations. `meta-mingw` still needs `libiconv`, so it has been moved to `meta-mingw`.

- `libpng12`: This recipe was previously needed for LSB. The current `libpng` is 1.6.x.

- `libpod-plainer-perl`: This recipe was previously needed for LSB 4, no longer needed.

- `linux-yocto (4.1)`: This recipe was removed in favor of 4.4, 4.9, 4.10 and 4.12.

- `mailx`: This recipe was previously only needed for LSB compatibility, and upstream is defunct.

- `mesa (git version only)`: The git version recipe was stale with respect to the release version.

- `ofono (git version only)`: The git version recipe was stale with respect to the release version.

- `portmap`: This recipe is obsolete and is superseded by `rpcbind`.

- `python3-pygpgme`: This recipe is old and unmaintained. It was previously required by `dnf`, which has switched to official `gpgme` Python bindings.

- `python-async`: This recipe has been removed in favor of the Python 3 version.

- `python-gitdb`: This recipe has been removed in favor of the Python 3 version.

- `python-git`: This recipe was removed in favor of the Python 3 version.

- `python-mako`: This recipe was removed in favor of the Python 3 version.

- `python-pexpect`: This recipe was removed in favor of the Python 3 version.

- `python-ptyprocess`: This recipe was removed in favor of Python the 3 version.

- `python-pycurl`: Nothing is using this recipe in OpenEmbedded-Core (i.e. `meta-oe`).

- `python-six`: This recipe was removed in favor of the Python 3 version.

- `python-smmap`: This recipe was removed in favor of the Python 3 version.

- `remake`: Using `remake` as the provider of `virtual/make` is broken. Consequently, this recipe is not needed in OpenEmbedded-Core.

### Kernel Device Tree Move

Kernel Device Tree support is now easier to enable in a kernel recipe. The Device Tree code has moved to a `kernel-devicetree` class. Functionality is automatically enabled for any recipe that inherits the `kernel` class and sets the `KERNEL_DEVICETREE` variable. The previous mechanism for doing this, `meta/recipes-kernel/linux/linux-dtb.inc`, is still available to avoid breakage, but triggers a deprecation warning. Future releases of the Yocto Project will remove `meta/recipes-kernel/linux/linux-dtb.inc`. It is advisable to remove any `require` statements that request `meta/recipes-kernel/linux/linux-dtb.inc` from any custom kernel recipes you might have. This will avoid breakage in post 2.4 releases.

### Package QA Changes

The following package QA changes took place:

- The "unsafe-references-in-scripts" QA check has been removed.

- If you refer to `${COREBASE}/LICENSE` within `LIC_FILES_CHKSUM` you receive a warning because this file is a description of the license for OE-Core. Use `${COMMON_LICENSE_DIR}/MIT` if your recipe is MIT-licensed and you cannot use the preferred method of referring to a file within the source tree.

### `README` File Changes

The following are changes to `README` files:

- The main Poky `README` file has been moved to the `meta-poky` layer and has been renamed `README.poky`. A symlink has been created so that references to the old location work.

- The `README.hardware` file has been moved to `meta-yocto-bsp`. A symlink has been created so that references to the old location work.

- A `README.qemu` file has been created with coverage of the `qemu*` machines.

### Miscellaneous Changes

The following are additional changes:

- The `ROOTFS_PKGMANAGE_BOOTSTRAP` variable and any references to it have been removed. You should remove this variable from any custom recipes.

- The `meta-yocto` directory has been removed.

  In the Yocto Project 2.1 release `meta-yocto` was renamed to `meta-poky` and the `meta-yocto` subdirectory remained to avoid breaking existing configurations.

- The `maintainers.inc` file, which tracks maintainers by listing a primary person responsible for each recipe in OE-Core, has been moved from `meta-poky` to OE-Core (i.e. from `meta-poky/conf/distro/include` to `meta/conf/distro/include`).

- The `buildhistory` class now makes a single commit per build rather than one commit per subdirectory in the repository. This behavior assumes the commits are enabled with `BUILDHISTORY_COMMIT` = "1", which is typical. Previously, the `buildhistory` class made one commit per subdirectory in the repository in order to make it easier to see the changes for a particular subdirectory. To view a particular change, specify that subdirectory as the last parameter on the `git show` or `git diff` commands.

- The `x86-base.inc` file, which is included by all x86-based machine configurations, now sets `IMAGE_FSTYPES` using `?=` to "live" rather than appending with `+=`. This change makes the default easier to override.

- BitBake fires multiple "BuildStarted" events when multiconfig is enabled (one per configuration). For more information, see the "Events" section in the BitBake User Manual.

- By default, the `security_flags.inc` file sets a `GCCPIE` variable with an option to enable Position Independent Executables (PIE) within `gcc`. Enabling PIE in the GNU C Compiler (GCC), makes Return Oriented Programming (ROP) attacks much more difficult to execute.

- OE-Core now provides a `bitbake-layers` plugin that implements a "create-layer" subcommand. The implementation of this subcommand has resulted in the `yocto-layer` script being deprecated and will likely be removed in the next Yocto Project release.

- The `vmdk`, `vdi`, and `qcow2` image file types are now used in conjunction with the "wic" image type through `CONVERSION_CMD`. Consequently, the equivalent image types are now `wic.vmdk`, `wic.vdi`, and `wic.qcow2`, respectively.

- `do_image_<type>[depends]` has replaced `IMAGE_DEPENDS_<type>`. If you have your own classes that implement custom image types, then you need to update them.

- OpenSSL 1.1 has been introduced. However, the default is still 1.0.x through the `PREFERRED_VERSION` variable. This preference is set is due to the remaining compatibility issues with other software. The `PROVIDES` variable in the openssl 1.0 recipe now includes "openssl10" as a marker that can be used in `DEPENDS` within recipes that build software that still depend on OpenSSL 1.0.

- To ensure consistent behavior, BitBake's "-r" and "-R" options (i.e. prefile and postfile), which are used to read or post-read additional configuration files from the command line, now only affect the current BitBake command. Before these BitBake changes, these options would "stick" for future executions.

## Moving to the Yocto Project 2.5 Release

This section provides migration information for moving to the Yocto Project 2.5 Release from the prior release.

### Packaging Changes

This section provides information about packaging changes that have occurred:

- `bind-libs`: The libraries packaged by the bind recipe are in a separate `bind-libs` package.

- `libfm-gtk`: The `libfm` GTK+ bindings are split into a separate `libfm-gtk` package.

- `flex-libfl`: The flex recipe splits out libfl into a separate `flex-libfl` package to avoid too many dependencies being pulled in where only the library is needed.

- `grub-efi`: The `grub-efi` configuration is split into a separate `grub-bootconf` recipe. However, the dependency relationship from `grub-efi` is through a virtual/grub-bootconf provider making it possible to have your own recipe provide the dependency. Alternatively, you can use a BitBake append file to bring the configuration back into the `grub-efi` recipe.

- armv7a Legacy Package Feed Support: Legacy support is removed for transitioning from `armv7a` to `armv7a-vfp-neon` in package feeds, which was previously enabled by setting `PKGARCHCOMPAT_ARMV7A`. This transition occurred in 2011 and active package feeds should by now be updated to the new naming.

### Removed Recipes

The following recipes have been removed:

- `gcc`: The version 6.4 recipes are replaced by 7.x.

- `gst-player`: Renamed to `gst-examples` as per upstream.

- `hostap-utils`: This software package is obsolete.

- `latencytop`: This recipe is no longer maintained upstream. The last release was in 2009.

- `libpfm4`: The only file that requires this recipe is `oprofile`, which has been removed.

- `linux-yocto`: The version 4.4, 4.9, and 4.10 recipes have been removed. Versions 4.12, 4.14, and 4.15 remain.

- `man`: This recipe has been replaced by modern `man-db`

- `mkelfimage`: This tool has been removed in the upstream coreboot project, and is no longer needed with the removal of the ELF image type.

- `nativesdk-postinst-intercept`: This recipe is not maintained.

- `neon`: This software package is no longer maintained upstream and is no longer needed by anything in OpenEmbedded-Core.

- `oprofile`: The functionality of this recipe is replaced by `perf` and keeping compatibility on an ongoing basis with `musl` is difficult.

- `pax`: This software package is obsolete.

- `stat`: This software package is not maintained upstream. `coreutils` provides a modern stat binary.

- `zisofs-tools-native`: This recipe is no longer needed because the compressed ISO image feature has been removed.

### Scripts and Tools Changes

The following are changes to scripts and tools:

- `yocto-bsp`, `yocto-kernel`, and `yocto-layer`: The `yocto-bsp`, `yocto-kernel`, and `yocto-layer` scripts previously shipped with poky but not in OpenEmbedded-Core have been removed. These scripts are not maintained and are outdated. In many cases, they are also limited in scope. The `bitbake-layers create-layer` command is a direct replacement for `yocto-layer`. See the documentation to create a BSP or kernel recipe in the "BSP Kernel Recipe Example" section.

- `devtool finish`: `devtool finish` now exits with an error if there are uncommitted changes or a rebase/am in progress in the recipe's source repository. If this error occurs, there might be uncommitted changes that will not be included in updates to the patches applied by the recipe. A -f/--force option is provided for situations that the uncommitted changes are inconsequential and you want to proceed regardless.

- `scripts/oe-setup-rpmrepo` script: The functionality of `scripts/oe-setup-rpmrepo` is replaced by `bitbake package-index`.

- `scripts/test-dependencies.sh` script: The script is largely made obsolete by the recipe-specific sysroots functionality introduced in the previous release.

### BitBake Changes

The following are BitBake changes:

- The `--runall` option has changed. There are two different behaviors people might want:

  - Behavior A: For a given target (or set of targets) look through the task graph and run task X only if it is present and will be built.

  - Behavior B: For a given target (or set of targets) look through the task graph and run task X if any recipe in the taskgraph has such a target, even if it is not in the original task graph.

  The `--runall` option now performs "Behavior B". Previously `--runall` behaved like "Behavior A". A `--runonly` option has been added to retain the ability to perform "Behavior A".

- Several explicit "run this task for all recipes in the dependency tree" tasks have been removed (e.g. `fetchall`, `checkuriall`, and the `*all` tasks provided by the `distrodata` and `archiver` classes). There is a BitBake option to complete this for any arbitrary task. For example:

           bitbake <target> -c fetchall

  should now be replaced with:

           bitbake <target> --runall=fetch

### Python and Python 3 Changes

The following are auto-packaging changes to Python and Python 3:

The script-managed `python-*-manifest.inc` files that were previously used to generate Python and Python 3 packages have been replaced with a JSON-based file that is easier to read and maintain. A new task is available for maintainers of the Python recipes to update the JSON file when upgrading to new Python versions. You can now edit the file directly instead of having to edit a script and run it to update the file.

One particular change to note is that the Python recipes no longer have build-time provides for their packages. This assumes `python-foo` is one of the packages provided by the Python recipe. You can no longer run `bitbake python-foo` or have a `DEPENDS` on `python-foo`, but doing either of the following causes the package to work as expected:

         IMAGE_INSTALL_append = " python-foo"

or

         RDEPENDS_${PN} = "python-foo"

The earlier build-time provides behavior was a quirk of the way the Python manifest file was created. For more information on this change please see this commit.

### Miscellaneous Changes

The following are additional changes:

- The `kernel` class supports building packages for multiple kernels. If your kernel recipe or `.bbappend` file mentions packaging at all, you should replace references to the kernel in package names with `${KERNEL_PACKAGE_NAME}`. For example, if you disable automatic installation of the kernel image using `RDEPENDS_kernel-base = ""` you can avoid warnings using `RDEPENDS_${KERNEL_PACKAGE_NAME}-base = ""` instead.

- The `buildhistory` class commits changes to the repository by default so you no longer need to set `BUILDHISTORY_COMMIT = "1"`. If you want to disable commits you need to set `BUILDHISTORY_COMMIT = "0"` in your configuration.

- The `beaglebone` reference machine has been renamed to `beaglebone-yocto`. The `beaglebone-yocto` BSP is a reference implementation using only mainline components available in OpenEmbedded-Core and `meta-yocto-bsp`, whereas Texas Instruments maintains a full-featured BSP in the `meta-ti` layer. This rename avoids the previous name clash that existed between the two BSPs.

- The `update-alternatives` class no longer works with SysV `init` scripts because this usage has been problematic. Also, the `sysklogd` recipe no longer uses `update-alternatives` because it is incompatible with other implementations.

- By default, the `cmake` class uses `ninja` instead of `make` for building. This improves build performance. If a recipe is broken with `ninja`, then the recipe can set `OECMAKE_GENERATOR = "Unix Makefiles"` to change back to `make`.

- The previously deprecated `base_*` functions have been removed in favor of their replacements in `meta/lib/oe` and `bitbake/lib/bb`. These are typically used from recipes and classes. Any references to the old functions must be updated. The following table shows the removed functions and their replacements:

           Removed                                 Replacement
           ============================            ============================
           base_path_join()                        oe.path.join()
           base_path_relative()                    oe.path.relative()
           base_path_out()                         oe.path.format_display()
           base_read_file()                        oe.utils.read_file()
           base_ifelse()                           oe.utils.ifelse()
           base_conditional()                      oe.utils.conditional()
           base_less_or_equal()                    oe.utils.less_or_equal()
           base_version_less_or_equal()            oe.utils.version_less_or_equal()
           base_contains()                         bb.utils.contains()
           base_both_contain()                     oe.utils.both_contain()
           base_prune_suffix()                     oe.utils.prune_suffix()
           oe_filter()                             oe.utils.str_filter()
           oe_filter_out()                         oe.utils.str_filter_out() (or use the _remove operator).

- Using `exit 1` to explicitly defer a postinstall script until first boot is now deprecated since it is not an obvious mechanism and can mask actual errors. If you want to explicitly defer a postinstall to first boot on the target rather than at `rootfs` creation time, use `pkg_postinst_ontarget()` or call `postinst_intercept delay_to_first_boot` from `pkg_postinst()`. Any failure of a `pkg_postinst()` script (including `exit 1`) will trigger a warning during `do_rootfs`.

  For more information, see the "Post-Installation Scripts" section in the Yocto Project Development Tasks Manual.

- The `elf` image type has been removed. This image type was removed because the `mkelfimage` tool that was required to create it is no longer provided by coreboot upstream and required updating every time `binutils` updated.

- Support for .iso image compression (previously enabled through `COMPRESSISO = "1"`) has been removed. The userspace tools (`zisofs-tools`) are unmaintained and `squashfs` provides better performance and compression. In order to build a live image with squashfs+lz4 compression enabled you should now set `LIVE_ROOTFS_TYPE = "squashfs-lz4"` and ensure that `live` is in `IMAGE_FSTYPES`.

- Recipes with an unconditional dependency on `libpam` are only buildable with `pam` in `DISTRO_FEATURES`. If the dependency is truly optional then it is recommended that the dependency be conditional upon `pam` being in `DISTRO_FEATURES`.

- For EFI-based machines, the bootloader (`grub-efi` by default) is installed into the image at /boot. Wic can be used to split the bootloader into separate boot and rootfs partitions if necessary.

- Patches whose context does not match exactly (i.e. where patch reports "fuzz" when applying) will generate a warning. For an example of this see this commit.

- Layers are expected to set `LAYERSERIES_COMPAT_layername` to match the version(s) of OpenEmbedded-Core they are compatible with. This is specified as codenames using spaces to separate multiple values (e.g. "rocko sumo"). If a layer does not set `LAYERSERIES_COMPAT_layername`, a warning will is shown. If a layer sets a value that does not include the current version ("sumo" for the 2.5 release), then an error will be produced.

- The `TZ` environment variable is set to "UTC" within the build environment in order to fix reproducibility problems in some recipes.

## Moving to the Yocto Project 2.6 Release

This section provides migration information for moving to the Yocto Project 2.6 Release from the prior release.

### GCC 8.2 is Now Used by Default

The GNU Compiler Collection version 8.2 is now used by default for compilation. For more information on what has changed in the GCC 8.x release, see .

If you still need to compile with version 7.x, GCC 7.3 is also provided. You can select this version by setting the and can be selected by setting the `GCCVERSION` variable to "7.%" in your configuration.

### Removed Recipes

The following recipes have been removed:

         beecrypt: No longer needed since moving to RPM 4.
         bigreqsproto: Replaced by xorgproto.
         calibrateproto: Removed in favor of xinput.
         compositeproto: Replaced by xorgproto.
         damageproto: Replaced by xorgproto.
         dmxproto: Replaced by xorgproto.
         dri2proto: Replaced by xorgproto.
         dri3proto: Replaced by xorgproto.
         eee-acpi-scripts: Became obsolete.
         fixesproto: Replaced by xorgproto.
         fontsproto: Replaced by xorgproto.
         fstests: Became obsolete.
         gccmakedep: No longer used.
         glproto: Replaced by xorgproto.
         gnome-desktop3: No longer needed.  This recipe has moved to meta-oe.
         icon-naming-utils: No longer used since the Sato theme was removed in 2016.
         inputproto: Replaced by xorgproto.
         kbproto: Replaced by xorgproto.
         libusb-compat: Became obsolete.
         libuser: Became obsolete.
         libnfsidmap: No longer an external requirement since nfs-utils 2.2.1.  libnfsidmap is now integrated.
         libxcalibrate: No longer needed with xinput
         mktemp: Became obsolete. The mktemp command is provided by both busybox and coreutils.
         ossp-uuid: Is not being maintained and has mostly been replaced by uuid.h in util-linux.
         pax-utils: No longer needed.  Previous QA tests that did use this recipe are now done at build time.
         pcmciautils: Became obsolete.
         pixz: No longer needed. xz now supports multi-threaded compression.
         presentproto: Replaced by xorgproto.
         randrproto: Replaced by xorgproto.
         recordproto: Replaced by xorgproto.
         renderproto: Replaced by xorgproto.
         resourceproto: Replaced by xorgproto.
         scrnsaverproto: Replaced by xorgproto.
         trace-cmd: Became obsolete.  perf replaced this recipe's functionally.
         videoproto: Replaced by xorgproto.
         wireless-tools: Became obsolete.  Superseded by iw.
         xcmiscproto: Replaced by xorgproto.
         xextproto: Replaced by xorgproto.
         xf86dgaproto: Replaced by xorgproto.
         xf86driproto: Replaced by xorgproto.
         xf86miscproto: Replaced by xorgproto.
         xf86-video-omapfb: Became obsolete.  Use kernel modesetting driver instead.
         xf86-video-omap: Became obsolete.  Use kernel modesetting driver instead.
         xf86vidmodeproto: Replaced by xorgproto.
         xineramaproto: Replaced by xorgproto.
         xproto: Replaced by xorgproto.
         yasm: No longer needed since previous usages are now satisfied by nasm.

### Packaging Changes

The following packaging changes have been made:

- `cmake`: `cmake.m4` and `toolchain` files have been moved to the main package.

- `iptables`: The `iptables` modules have been split into separate packages.

- `alsa-lib`: `libasound` is now in the main `alsa-lib` package instead of `libasound`.

- `glibc`: `libnss-db` is now in its own package along with a `/var/db/makedbs.sh` script to update databases.

- `python` and `python3`: The main package has been removed from the recipe. You must install specific packages or `python-modules` / `python3-modules` for everything.

- `systemtap`: Moved `systemtap-exporter` into its own package.

### XOrg Protocol dependencies

The "*proto" upstream repositories have been combined into one "xorgproto" repository. Thus, the corresponding recipes have also been combined into a single `xorgproto` recipe. Any recipes that depend upon the older `*proto` recipes need to be changed to depend on the newer `xorgproto` recipe instead.

For names of recipes removed because of this repository change, see the Removed Recipes section.

### `distutils` and `distutils3` Now Prevent Fetching Dependencies During the `do_configure` Task

Previously, it was possible for Python recipes that inherited the `distutils` and `distutils3` classes to fetch code during the `do_configure` task to satisfy dependencies mentioned in `setup.py` if those dependencies were not provided in the sysroot (i.e. recipes providing the dependencies were missing from `DEPENDS`).

This change affects classes beyond just the two mentioned (i.e. `distutils` and `distutils3`). Any recipe that inherits `distutils*` classes are affected. For example, the `setuptools` and `setuptools3` recipes are affected since they inherit the `distutils*` classes.

Fetching these types of dependencies that are not provided in the sysroot negatively affects the ability to reproduce builds. This type of fetching is now explicitly disabled. Consequently, any missing dependencies in Python recipes that use these classes now result in an error during the `do_configure` task.

### `linux-yocto` Configuration Audit Issues Now Correctly Reported

Due to a bug, the kernel configuration audit functionality was not writing out any resulting warnings during the build. This issue is now corrected. You might notice these warnings now if you have a custom kernel configuration with a `linux-yocto` style kernel recipe.

### Image/Kernel Artifact Naming Changes

The following changes have been made:

- Name variables (e.g. `IMAGE_NAME`) use a new `IMAGE_VERSION_SUFFIX` variable instead of `DATETIME`. Using `IMAGE_VERSION_SUFFIX` allows easier and more direct changes.

  The `IMAGE_VERSION_SUFFIX` variable is set in the `bitbake.conf` configuration file as follows:

           IMAGE_VERSION_SUFFIX = "-${DATETIME}"

- Several variables have changed names for consistency:

          Old Variable Name               New Variable Name
          ========================================================
          KERNEL_IMAGE_BASE_NAME          KERNEL_IMAGE_NAME
          KERNEL_IMAGE_SYMLINK_NAME       KERNEL_IMAGE_LINK_NAME
          MODULE_TARBALL_BASE_NAME        MODULE_TARBALL_NAME
          MODULE_TARBALL_SYMLINK_NAME     MODULE_TARBALL_LINK_NAME
          INITRAMFS_BASE_NAME             INITRAMFS_NAME

- The `MODULE_IMAGE_BASE_NAME` variable has been removed. The module tarball name is now controlled directly with the `MODULE_TARBALL_NAME` variable.

- The `KERNEL_DTB_NAME` and `KERNEL_DTB_LINK_NAME` variables have been introduced to control kernel Device Tree Binary (DTB) artifact names instead of mangling `KERNEL_IMAGE_*` variables.

- The `KERNEL_FIT_NAME` and `KERNEL_FIT_LINK_NAME` variables have been introduced to specify the name of flattened image tree (FIT) kernel images similar to other deployed artifacts.

- The `MODULE_TARBALL_NAME` and `MODULE_TARBALL_LINK_NAME` variable values no longer include the "module-" prefix or ".tgz" suffix. These parts are now hardcoded so that the values are consistent with other artifact naming variables.

- Added the `INITRAMFS_LINK_NAME` variable so that the symlink can be controlled similarly to other artifact types.

- `INITRAMFS_NAME` now uses "${PKGE}-${PKGV}-${PKGR}-${MACHINE}${IMAGE_VERSION_SUFFIX}" instead of "${PV}-${PR}-${MACHINE}-${DATETIME}", which makes it consistent with other variables.

### `SERIAL_CONSOLE` Deprecated

The `SERIAL_CONSOLE` variable has been functionally replaced by the `SERIAL_CONSOLES` variable for some time. With the Yocto Project 2.6 release, `SERIAL_CONSOLE` has been officially deprecated.

`SERIAL_CONSOLE` will continue to work as before for the 2.6 release. However, for the sake of future compatibility, it is recommended that you replace all instances of `SERIAL_CONSOLE` with `SERIAL_CONSOLES`.

The only difference in usage is that `SERIAL_CONSOLES` expects entries to be separated using semicolons as compared to `SERIAL_CONSOLE`, which expects spaces.

### Configure Script Reports Unknown Options as Errors

If the configure script reports an unknown option, this now triggers a QA error instead of a warning. Any recipes that previously got away with specifying such unknown options now need to be fixed.

### Override Changes

The following changes have occurred:

- The `virtclass-native` and `virtclass-nativesdk` Overrides Have Been Removed: The `virtclass-native` and `virtclass-nativesdk` overrides have been deprecated since 2012 in favor of `class-native` and `class-nativesdk`, respectively. Both `virtclass-native` and `virtclass-nativesdk` are now dropped.

  The `virtclass-multilib-` overrides for multilib are still valid.

- The `forcevariable` Override Now Has a Higher Priority Than `libc` Overrides: The `forcevariable` override is documented to be the highest priority override. However, due to a long-standing quirk of how `OVERRIDES` is set, the `libc` overrides (e.g. `libc-glibc`, `libc-musl`, and so forth) erroneously had a higher priority. This issue is now corrected.

  It is likely this change will not cause any problems. However, it is possible with some unusual configurations that you might see a change in behavior if you were relying on the previous behavior. Be sure to check how you use `forcevariable` and `libc-*` overrides in your custom layers and configuration files to ensure they make sense.

- The `build-${BUILD_OS}` Override Has Been Removed: The `build-${BUILD_OS}`, which is typically `build-linux`, override has been removed because building on a host operating system other than a recent version of Linux is neither supported nor recommended. Dropping the override avoids giving the impression that other host operating systems might be supported.

- The "_remove" operator now preserves whitespace. Consequently, when specifying list items to remove, be aware that leading and trailing whitespace resulting from the removal is retained.

  See the "Removal (Override Style Syntax)" section in the BitBake User Manual for a detailed example.

### `systemd` Configuration is Now Split Into `systemd-conf`

The configuration for the `systemd` recipe has been moved into a `system-conf` recipe. Moving this configuration to a separate recipe avoids the `systemd` recipe from becoming machine-specific for cases where machine-specific configurations need to be applied (e.g. for `qemu*` machines).

Currently, the new recipe packages the following files:

         ${sysconfdir}/machine-id
         ${sysconfdir}/systemd/coredump.conf
         ${sysconfdir}/systemd/journald.conf
         ${sysconfdir}/systemd/logind.conf
         ${sysconfdir}/systemd/system.conf
         ${sysconfdir}/systemd/user.conf

If you previously used bbappend files to append the `systemd` recipe to change any of the listed files, you must do so for the `systemd-conf` recipe instead.

### Automatic Testing Changes

This section provides information about automatic testing changes:

- `TEST_IMAGE` Variable Removed: Prior to this release, you set the `TEST_IMAGE` variable to "1" to enable automatic testing for successfully built images. The `TEST_IMAGE` variable no longer exists and has been replaced by the `TESTIMAGE_AUTO` variable.

- Inheriting the `testimage` and `testsdk` Classes: Best practices now dictate that you use the `IMAGE_CLASSES` variable rather than the `INHERIT` variable when you inherit the `testimage` and `testsdk` classes used for automatic testing.

### OpenSSL Changes

OpenSSL has been upgraded from 1.0 to 1.1. By default, this upgrade could cause problems for recipes that have both versions in their dependency chains. The problem is that both versions cannot be installed together at build time.

It is possible to have both versions of the library at runtime.

### BitBake Changes

The server logfile `bitbake-cookerdaemon.log` is now always placed in the Build Directory instead of the current directory.

### Security Changes

The Poky distribution now uses security compiler flags by default. Inclusion of these flags could cause new failures due to stricter checking for various potential security issues in code.

### Post Installation Changes

You must explicitly mark post installs to defer to the target. If you want to explicitly defer a postinstall to first boot on the target rather than at rootfs creation time, use `pkg_postinst_ontarget()` or call `postinst_intercept delay_to_first_boot` from `pkg_postinst()`. Any failure of a `pkg_postinst()` script (including exit 1) triggers an error during the `do_rootfs` task.

For more information on post-installation behavior, see the "Post-Installation Scripts" section in the Yocto Project Development Tasks Manual.

### Python 3 Profile-Guided Optimization

The `python3` recipe now enables profile-guided optimization. Using this optimization requires a little extra build time in exchange for improved performance on the target at runtime. Additionally, the optimization is only enabled if the current `MACHINE` has support for user-mode emulation in QEMU (i.e. "qemu-usermode" is in `MACHINE_FEATURES`, which it is by default).

If you wish to disable Python profile-guided optimization regardless of the value of `MACHINE_FEATURES`, then ensure that `PACKAGECONFIG` for the `python3` recipe does not contain "pgo". You could accomplish the latter using the following at the configuration level:

         PACKAGECONFIG_remove_pn-python3 = "pgo"

Alternatively, you can set `PACKAGECONFIG` using an append file for the `python3` recipe.

### Miscellaneous Changes

The following miscellaneous changes occurred:

- Default to using the Thumb-2 instruction set for armv7a and above. If you have any custom recipes that build software that needs to be built with the ARM instruction set, change the recipe to set the instruction set as follows:

           ARM_INSTRUCTION_SET = "arm"

- `run-postinsts` no longer uses `/etc/*-postinsts` for `dpkg/opkg` in favor of built-in postinst support. RPM behavior remains unchanged.

- The `NOISO` and `NOHDD` variables are no longer used. You now control building `*.iso` and `*.hddimg` image types directly by using the `IMAGE_FSTYPES` variable.

- The `scripts/contrib/mkefidisk.sh` has been removed in favor of Wic.

- `kernel-modules` has been removed from `RRECOMMENDS` for `qemumips` and `qemumips64` machines. Removal also impacts the `x86-base.inc` file.

  `genericx86` and `genericx86-64` retain `kernel-modules` as part of the `RRECOMMENDS` variable setting.

- The `LGPLv2_WHITELIST_GPL-3.0` variable has been removed. If you are setting this variable in your configuration, set or append it to the `WHITELIST_GPL-3.0` variable instead.

- `${ASNEEDED}` is now included in the `TARGET_LDFLAGS` variable directly. The remaining definitions from `meta/conf/distro/include/as-needed.inc` have been moved to corresponding recipes.

- Support for DSA host keys has been dropped from the OpenSSH recipes. If you are still using DSA keys, you must switch over to a more secure algorithm as recommended by OpenSSH upstream.

- The `dhcp` recipe now uses the `dhcpd6.conf` configuration file in `dhcpd6.service` for IPv6 DHCP rather than re-using `dhcpd.conf`, which is now reserved for IPv4.

## Moving to the Yocto Project 2.7 Release

This section provides migration information for moving to the Yocto Project 2.7 Release from the prior release.

### BitBake Changes

The following changes have been made to BitBake:

- BitBake now checks anonymous Python functions and pure Python functions (e.g. `def funcname:`) in the metadata for tab indentation. If found, BitBake produces a warning.

- Bitbake now checks `BBFILE_COLLECTIONS` for duplicate entries and triggers an error if any are found.

### Eclipse Support Removed

Support for the Eclipse IDE has been removed. Support continues for those releases prior to 2.7 that did include support. The 2.7 release does not include the Eclipse Yocto plugin.

### `qemu-native` Splits the System and User-Mode Parts

The system and user-mode parts of `qemu-native` are now split. `qemu-native` provides the user-mode components and `qemu-system-native` provides the system components. If you have recipes that depend on QEMU's system emulation functionality at build time, they should now depend upon `qemu-system-native` instead of `qemu-native`.

### The `upstream-tracking.inc` File Has Been Removed

The previously deprecated `upstream-tracking.inc` file is now removed. Any `UPSTREAM_TRACKING*` variables are now set in the corresponding recipes instead.

Remove any references you have to the `upstream-tracking.inc` file in your configuration.

### The `DISTRO_FEATURES_LIBC` Variable Has Been Removed

The `DISTRO_FEATURES_LIBC` variable is no longer used. The ability to configure glibc using kconfig has been removed for quite some time making the `libc-*` features set no longer effective.

Remove any references you have to `DISTRO_FEATURES_LIBC` in your own layers.

### License Value Corrections

The following corrections have been made to the `LICENSE` values set by recipes:

         socat: Corrected LICENSE to be "GPLv2" rather than
            "GPLv2+".

         libgfortran: Set license to "GPL-3.0-with-GCC-exception".

         elfutils: Removed "Elfutils-Exception" and set to "GPLv2" for shared
            libraries

### Packaging Changes

This section provides information about packaging changes.

- `bind`: The `nsupdate` binary has been moved to the `bind-utils` package.

- Debug split: The default debug split has been changed to create separate source packages (i.e. package_name`-dbg` and package_name`-src`). If you are currently using `dbg-pkgs` in `IMAGE_FEATURES` to bring in debug symbols and you still need the sources, you must now also add `src-pkgs` to `IMAGE_FEATURES`. Source packages remain in the target portion of the SDK by default, unless you have set your own value for `SDKIMAGE_FEATURES` that does not include `src-pkgs`.

- Mount all using `util-linux`: `/etc/default/mountall` has moved into the -mount sub-package.

- Splitting binaries using `util-linux`: `util-linux` now splits each binary into its own package for fine-grained control. The main `util-linux` package pulls in the individual binary packages using the `RRECOMMENDS` and `RDEPENDS` variables. As a result, existing images should not see any changes assuming `NO_RECOMMENDATIONS` is not set.

- `netbase/base-files`: `/etc/hosts` has moved from `netbase` to `base-files`.

- `tzdata`: The main package has been converted to an empty meta package that pulls in all `tzdata` packages by default.

- `lrzsz`: This package has been removed from `packagegroup-self-hosted` and `packagegroup-core-tools-testapps`. The X/Y/ZModem support is less likely to be needed on modern systems. If you are relying on these packagegroups to include the `lrzsz` package in your image, you now need to explicitly add the package.

### Removed Recipes

The following recipes have been removed:

         gcc: Drop version 7.3 recipes. Version 8.3 now remains.

         linux-yocto: Drop versions 4.14 and 4.18 recipes. Versions 4.19 and 5.0 remain.

         go: Drop version 1.9 recipes. Versions 1.11 and 1.12 remain.

         xvideo-tests: Became obsolete.

         libart-lgpl: Became obsolete.

         gtk-icon-utils-native: These tools are now provided by gtk+3-native

         gcc-cross-initial: No longer needed. gcc-cross/gcc-crosssdk is now used instead.

         gcc-crosssdk-initial: No longer needed. gcc-cross/gcc-crosssdk is now used instead.

         glibc-initial: Removed because the benefits of having it for site_config are
            currently outweighed by the cost of building the recipe.

### Removed Classes

The following classes have been removed:

         distutils-tools: This class was never used.

         bugzilla.bbclass: Became obsolete.

         distrodata: This functionally has been replaced by a more modern
             tinfoil-based implementation.

### Miscellaneous Changes

The following miscellaneous changes occurred:

- The `distro` subdirectory of the Poky repository has been removed from the top-level `scripts` directory.

- Perl now builds for the target using `perl-cross` for better maintainability and improved build performance. This change should not present any problems unless you have heavily customized your Perl recipe.

- `arm-tunes`: Removed the "-march" option if mcpu is already added.

- `update-alternatives`: Convert file renames to `PACKAGE_PREPROCESS_FUNCS`

- `base/pixbufcache`: Obsolete `sstatecompletions` code has been removed.

- `native` class: `RDEPENDS` handling has been enabled.

- `inetutils`: This recipe has rsh disabled.

## Moving to the Yocto Project 3.0 Release

This section provides migration information for moving to the Yocto Project 3.0 Release from the prior release.

### Init System Selection

Changing the init system manager previously required setting a number of different variables. You can now change the manager by setting the `INIT_MANAGER` variable and the corresponding include files (i.e. `conf/distro/include/init-manager-*.conf`). Include files are provided for four values: "none", "sysvinit", "systemd", and "mdev-busybox". The default value, "none", for `INIT_MANAGER` should allow your current settings to continue working. However, it is advisable to explicitly set `INIT_MANAGER`.

### LSB Support Removed

Linux Standard Base (LSB) as a standard is not current, and is not well suited for embedded applications. Support can be continued in a separate layer if needed. However, presently LSB support has been removed from the core.

As a result of this change, the `poky-lsb` derivative distribution configuration that was also used for testing alternative configurations has been replaced with a `poky-altcfg` distribution that has LSB parts removed.

### Removed Recipes

The following recipes have been removed.

- `core-image-lsb-dev`: Part of removed LSB support.

- `core-image-lsb`: Part of removed LSB support.

- `core-image-lsb-sdk`: Part of removed LSB support.

- `cve-check-tool`: Functionally replaced by the `cve-update-db` recipe and `cve-check` class.

- `eglinfo`: No longer maintained. `eglinfo` from `mesa-demos` is an adequate and maintained alternative.

- `gcc-8.3`: Version 8.3 removed. Replaced by 9.2.

- `gnome-themes-standard`: Only needed by gtk+ 2.x, which has been removed.

- `gtk+`: GTK+ 2 is obsolete and has been replaced by gtk+3.

- `irda-utils`: Has become obsolete. IrDA support has been removed from the Linux kernel in version 4.17 and later.

- `libnewt-python`: `libnewt` Python support merged into main `libnewt` recipe.

- `libsdl`: Replaced by newer `libsdl2`.

- `libx11-diet`: Became obsolete.

- `libxx86dga`: Removed obsolete client library.

- `libxx86misc`: Removed. Library is redundant.

- `linux-yocto`: Version 5.0 removed, which is now redundant (5.2 / 4.19 present).

- `lsbinitscripts`: Part of removed LSB support.

- `lsb`: Part of removed LSB support.

- `lsbtest`: Part of removed LSB support.

- `openssl10`: Replaced by newer `openssl` version 1.1.

- `packagegroup-core-lsb`: Part of removed LSB support.

- `python-nose`: Removed the Python 2.x version of the recipe.

- `python-numpy`: Removed the Python 2.x version of the recipe.

- `python-scons`: Removed the Python 2.x version of the recipe.

- `source-highlight`: No longer needed.

- `stress`: Replaced by `stress-ng`.

- `vulkan`: Split into `vulkan-loader`, `vulkan-headers`, and `vulkan-tools`.

- `weston-conf`: Functionality moved to `weston-init`.

### Packaging Changes

The following packaging changes have occurred.

- The Epiphany browser has been dropped from `packagegroup-self-hosted` as it has not been needed inside `build-appliance-image` for quite some time and was causing resource problems.

- `libcap-ng` Python support has been moved to a separate `libcap-ng-python` recipe to streamline the build process when the Python bindings are not needed.

- `libdrm` now packages the file `amdgpu.ids` into a separate `libdrm-amdgpu` package.

- `python3`: The `runpy` module is now in the `python3-core` package as it is required to support the common "python3 -m" command usage.

- `distcc` now provides separate `distcc-client` and `distcc-server` packages as typically one or the other are needed, rather than both.

- `python*-setuptools` recipes now separately package the `pkg_resources` module in a `python-pkg-resources` / `python3-pkg-resources` package as the module is useful independent of the rest of the setuptools package. The main `python-setuptools` / `python3-setuptools` package depends on this new package so you should only need to update dependencies unless you want to take advantage of the increased granularity.

### CVE Checking

`cve-check-tool` has been functionally replaced by a new `cve-update-db` recipe and functionality built into the `cve-check` class. The result uses NVD JSON data feeds rather than the deprecated XML feeds that `cve-check-tool` was using, supports CVSSv3 scoring, and makes other improvements.

Additionally, the `CVE_CHECK_CVE_WHITELIST` variable has been replaced by `CVE_CHECK_WHITELIST`.

### Bitbake Changes

The following BitBake changes have occurred.

- `addtask` statements now properly validate dependent tasks. Previously, an invalid task was silently ignored. With this change, the invalid task generates a warning.

- Other invalid `addtask` and `deltask` usages now trigger these warnings: "multiple target tasks arguments with addtask / deltask", and "multiple before/after clauses".

- The "multiconfig" prefix is now shortened to "mc". "multiconfig" will continue to work, however it may be removed in a future release.

- The `bitbake -g` command no longer generates a `recipe-depends.dot` file as the contents (i.e. a reprocessed version of `task-depends.dot`) were confusing.

- The `bb.build.FuncFailed` exception, previously raised by `bb.build.exec_func()` when certain other exceptions have occurred, has been removed. The real underlying exceptions will be raised instead. If you have calls to `bb.build.exec_func()` in custom classes or `tinfoil-using` scripts, any references to `bb.build.FuncFailed` should be cleaned up.

- Additionally, the `bb.build.exec_func()` no longer accepts the "pythonexception" parameter. The function now always raises exceptions. Remove this argument in any calls to `bb.build.exec_func()` in custom classes or scripts.

- The `BB_SETSCENE_VERIFY_FUNCTION2` is no longer used. In the unlikely event that you have any references to it, they should be removed.

- The `RunQueueExecuteScenequeue` and `RunQueueExecuteTasks` events have been removed since setscene tasks are now executed as part of the normal runqueue. Any event handling code in custom classes or scripts that handles these two events need to be updated.

- The arguments passed to functions used with `BB_HASHCHECK_FUNCTION` have changed. If you are using your own custom hash check function, see for details.

- Task specifications in `BB_TASKDEPDATA` and class implementations used in signature generator classes now use "<fn>:<task>" everywhere rather than the "." delimiter that was being used in some places. This change makes it consistent with all areas in the code. Custom signature generator classes and code that reads `BB_TASKDEPDATA` need to be updated to use ':' as a separator rather than '.'.

### Sanity Checks

The following sanity check changes occurred.

- `SRC_URI` is now checked for usage of two problematic items:

  - "${PN}" prefix/suffix use - Warnings always appear if ${PN} is used. You must fix the issue regardless of whether multiconfig or anything else that would cause prefixing/suffixing to happen.

  - Github archive tarballs - these are not guaranteed to be stable. Consequently, it is likely that the tarballs will be refreshed and thus the SRC_URI checksums will fail to apply. It is recommended that you fetch either an official release tarball or a specific revision from the actual Git repository instead.

  Either one of these items now trigger a warning by default. If you wish to disable this check, remove `src-uri-bad` from `WARN_QA`.

- The `file-rdeps` runtime dependency check no longer expands `RDEPENDS` recursively as there is no mechanism to ensure they can be fully computed, and thus races sometimes result in errors either showing up or not. Thus, you might now see errors for missing runtime dependencies that were previously satisfied recursively. Here is an example: package A contains a shell script starting with `#!/bin/bash` but has no dependency on bash. However, package A depends on package B, which does depend on bash. You need to add the missing dependency or dependencies to resolve the warning.

- Setting `DEPENDS_${PN}` anywhere (i.e. typically in a recipe) now triggers an error. The error is triggered because `DEPENDS` is not a package-specific variable unlike RDEPENDS. You should set `DEPENDS` instead.

- systemd currently does not work well with the musl C library because only upstream officially supports linking the library with glibc. Thus, a warning is shown when building systemd in conjunction with musl.

### Miscellaneous Changes

The following miscellaneous changes have occurred.

- The `gnome` class has been removed because it now does very little. You should update recipes that previously inherited this class to do the following:

           inherit gnomebase gtk-icon-cache gconf mime

- The `meta/recipes-kernel/linux/linux-dtb.inc` file has been removed. This file was previously deprecated in favor of setting `KERNEL_DEVICETREE` in any kernel recipe and only produced a warning. Remove any `include` or `require` statements pointing to this file.

- `TARGET_CFLAGS`, `TARGET_CPPFLAGS`, `TARGET_CXXFLAGS`, and `TARGET_LDFLAGS` are no longer exported to the external environment. This change did not require any changes to core recipes, which is a good indicator that no changes will be required. However, if for some reason the software being built by one of your recipes is expecting these variables to be set, then building the recipe will fail. In such cases, you must either export the variable or variables in the recipe or change the scripts so that exporting is not necessary.

- You must change the host distro identifier used in `NATIVELSBSTRING` to use all lowercase characters even if it does not contain a version number. This change is necessary only if you are not using `uninative` and `SANITY_TESTED_DISTROS`.

- In the `base-files` recipe, writing the hostname into `/etc/hosts` and `/etc/hostname` is now done within the main `do_install` function rather than in the `do_install_basefilesissue` function. The reason for the change is because `do_install_basefilesissue` is more easily overridden without having to duplicate the hostname functionality. If you have done the latter (e.g. in a `base-files` bbappend), then you should remove it from your customized `do_install_basefilesissue` function.

- The `wic --expand` command now uses commas to separate "key:value" pairs rather than hyphens.

  The wic command-line help is not updated.
  You must update any scripts or commands where you use `wic --expand` with multiple "key:value" pairs.

- UEFI image variable settings have been moved from various places to a central `conf/image-uefi.conf`. This change should not influence any existing configuration as the `meta/conf/image-uefi.conf` in the core metadata sets defaults that can be overridden in the same manner as before.

- `conf/distro/include/world-broken.inc` has been removed. For cases where certain recipes need to be disabled when using the musl C library, these recipes now have `COMPATIBLE_HOST_libc-musl` set with a comment that explains why.

## Moving to the Yocto Project 3.1 Release

This section provides migration information for moving to the Yocto Project 3.1 Release from the prior release.

### Minimum system requirements

The following versions / requirements of build host components have been updated:

- gcc 5.0

- python 3.5

- tar 1.28

- `rpcgen` is now required on the host (part of the `libc-dev-bin` package on Ubuntu, Debian and related distributions, and the `glibc` package on RPM-based distributions).

Additionally, the `makeinfo` and `pod2man` tools are no longer required on the host.

### mpc8315e-rdb machine removed

The MPC8315E-RDB machine is old/obsolete and unobtainable, thus given the maintenance burden the `mpc8315e-rdb` machine configuration that supported it has been removed in this release. The removal does leave a gap in official PowerPC reference hardware support; this may change in future if a suitable machine with accompanying support resources is found.

### Python 2 removed

Due to the expiration of upstream support in January 2020, support for Python 2 has now been removed; it is recommended that you use Python 3 instead. If absolutely needed there is a meta-python2 community layer containing Python 2, related classes and various Python 2-based modules, however it should not be considered as supported.

### Reproducible builds now enabled by default

In order to avoid unnecessary differences in output files (aiding binary reproducibility), the Poky distribution configuration (`DISTRO = "poky"`) now inherits the `reproducible_build` class by default.

### Impact of ptest feature is now more significant

The Poky distribution configuration (`DISTRO = "poky"`) enables ptests by default to enable runtime testing of various components. In this release, a dependency needed to be added that has resulted in a significant increase in the number of components that will be built just when building a simple image such as core-image-minimal. If you do not need runtime tests enabled for core components, then it is recommended that you remove "ptest" from `DISTRO_FEATURES` to save a significant amount of build time e.g. by adding the following in your configuration:

          DISTRO_FEATURES_remove = "ptest"

### Removed recipes

The following recipes have been removed:

- `chkconfig`: obsolete

- `console-tools`: obsolete

- `enchant`: replaced by `enchant2`

- `foomatic-filters`: obsolete

- `libidn`: no longer needed, moved to meta-oe

- `libmodulemd`: replaced by `libmodulemd-v1`

- `linux-yocto`: drop 4.19, 5.2 version recipes (5.4 now provided)

- `nspr`: no longer needed, moved to meta-oe

- `nss`: no longer needed, moved to meta-oe

- `python`: Python 2 removed (Python 3 preferred)

- `python-setuptools`: Python 2 version removed (python3-setuptools preferred)

- `sysprof`: no longer needed, moved to meta-oe

- `texi2html`: obsolete

- `u-boot-fw-utils`: functionally replaced by `libubootenv`

### features_check class replaces distro_features_check

The `distro_features_check` class has had its functionality expanded, now supporting `ANY_OF_MACHINE_FEATURES`, `REQUIRED_MACHINE_FEATURES`, `CONFLICT_MACHINE_FEATURES`, `ANY_OF_COMBINED_FEATURES`, `REQUIRED_COMBINED_FEATURES`, `CONFLICT_COMBINED_FEATURES`. As a result the class has now been renamed to `features_check`; the `distro_features_check` class still exists but generates a warning and redirects to the new class. In preparation for a future removal of the old class it is recommended that you update recipes currently inheriting `distro_features_check` to inherit `features_check` instead.

### Removed classes

The following classes have been removed:

- `distutils-base`: moved to meta-python2

- `distutils`: moved to meta-python2

- `libc-common`: merged into the glibc recipe as nothing else used it.

- `python-dir`: moved to meta-python2

- `pythonnative`: moved to meta-python2

- `setuptools`: moved to meta-python2

- `tinderclient`: dropped as it was obsolete.

### SRC_URI checksum behaviour

Previously, recipes by tradition included both SHA256 and MD5 checksums for remotely fetched files in `SRC_URI`, even though only one is actually mandated. However, the MD5 checksum does not add much given its inherent weakness; thus when a checksum fails only the SHA256 sum will now be printed. The md5sum will still be verified if it is specified.

### npm fetcher changes

The npm fetcher has been completely reworked in this release. The npm fetcher now only fetches the package source itself and no longer the dependencies; there is now also an npmsw fetcher which explicitly fetches the shrinkwrap file and the dependencies. This removes the slightly awkward `NPM_LOCKDOWN` and `NPM_SHRINKWRAP` variables which pointed to local files; the lockdown file is no longer needed at all. Additionally, the package name in `npm://` entries in `SRC_URI` is now specified using a `package` parameter instead of the earlier `name` which overlapped with the generic `name` parameter. All recipes using the npm fetcher will need to be changed as a result.

An example of the new scheme:

    SRC_URI = "npm://registry.npmjs.org;package=array-flatten;version=1.1.1 \
               npmsw://${THISDIR}/npm-shrinkwrap.json"

Another example where the sources are fetched from git rather than an npm repository:

    SRC_URI = "git://github.com/foo/bar.git;protocol=https \
               npmsw://${THISDIR}/npm-shrinkwrap.json"

devtool and recipetool have also been updated to match with the npm fetcher changes. Other than producing working and more complete recipes for npm sources, there is also a minor change to the command line for devtool: the `--fetch-dev` option has been renamed to `--npm-dev` as it is npm-specific.

### Packaging changes

- `intltool` has been removed from `packagegroup-core-sdk` as it is rarely needed to build modern software - gettext can do most of the things it used to be needed for. `intltool` has also been removed from `packagegroup-core-self-hosted` as it is not needed to for standard builds.

- git: `git-am`, `git-difftool`, `git-submodule`, and `git-request-pull` are no longer perl-based, so are now installed with the main `git` package instead of within `git-perltools`.

- The `ldconfig` binary built as part of glibc has now been moved to its own `ldconfig` package (note no `glibc-` prefix). This package is in the `RRECOMMENDS` of the main `glibc` package if `ldconfig` is present in `DISTRO_FEATURES`.

- `libevent` now splits each shared library into its own package (as Debian does). Since these are shared libraries and will be pulled in through the normal shared library dependency handling, there should be no impact to existing configurations other than less unnecessary libraries being installed in some cases.

- linux-firmware now has a new package for `bcm4366c` and includes available NVRAM config files into the `bcm43340`, `bcm43362`, `bcm43430` and `bcm4356-pcie` packages.

- `harfbuzz` now splits the new `libharfbuzz-subset.so` library into its own package to reduce the main package size in cases where `libharfbuzz-subset.so` is not needed.

### Additional warnings

Warnings will now be shown at `do_package_qa` time in the following circumstances:

- A recipe installs `.desktop` files containing `MimeType` keys but does not inherit the new `mime-xdg` class

- A recipe installs `.xml` files into `${datadir}/mime/packages` but does not inherit the `mime` class

### `wic` image type now used instead of `live` by default for x86

`conf/machine/include/x86-base.inc` (inherited by most x86 machine configurations) now specifies `wic` instead of `live` by default in `IMAGE_FSTYPES`. The `live` image type will likely be removed in a future release so it is recommended that you use `wic` instead.

### Miscellaneous changes

- The undocumented `SRC_DISTRIBUTE_LICENSES` variable has now been removed in favour of a new `AVAILABLE_LICENSES` variable which is dynamically set based upon license files found in `${COMMON_LICENSE_DIR}` and `${LICENSE_PATH}`.

- The tune definition for big-endian microblaze machines is now `microblaze` instead of `microblazeeb`.

- `newlib` no longer has built-in syscalls. `libgloss` should then provide the syscalls, `crt0.o` and other functions that are no longer part of `newlib` itself. If you are using `TCLIBC = "newlib"` this now means that you must link applications with both `newlib` and `libgloss`, whereas before `newlib` would run in many configurations by itself.