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+Release 2.1 (krogoth)
+=====================
+
+This section provides migration information for moving to the Yocto
+Project 2.1 Release (codename "krogoth") from the prior release.
+
+.. _migration-2.1-variable-expansion-in-python-functions:
+
+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()``.
+
+.. _migration-2.1-overrides-must-now-be-lower-case:
+
+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 :term:`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).
+
+.. _migration-2.1-expand-parameter-to-getvar-and-getvarflag-now-mandatory:
+
+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 *`
+
+.. note::
+
+   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.
+
+.. _migration-2.1-makefile-environment-changes:
+
+Makefile Environment Changes
+----------------------------
+
+:term:`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.
+
+.. _migration-2.1-libexecdir-reverted-to-prefix-libexec:
+
+``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 ``${libdir}``. The use is also contrary to the
+GNU Coding Standards (i.e.
+https://www.gnu.org/prep/standards/html_node/Directory-Variables.html)
+that suggest ``${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.
+https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s07.html) now
+recognizes the use of ``${prefix}/libexec/``, giving distributions the
+choice between ``${prefix}/lib`` or ``${prefix}/libexec`` without
+breaking FHS.
+
+.. _migration-2.1-ac-cv-sizeof-off-t-no-longer-cached-in-site-files:
+
+``ac_cv_sizeof_off_t`` is No Longer Cached in Site Files
+--------------------------------------------------------
+
+For recipes inheriting the :ref:`autotools <ref-classes-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 :ref:`ref-tasks-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.
+
+.. _migration-2.1-image-generation-split-out-from-filesystem-generation:
+
+Image Generation is Now Split Out from Filesystem Generation
+------------------------------------------------------------
+
+Previously, for image recipes the :ref:`ref-tasks-rootfs`
+task assembled the filesystem and then from that filesystem generated
+images. With this Yocto Project release, image generation is split into
+separate :ref:`ref-tasks-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
+:ref:`ref-tasks-image-complete` task rather than
+after ``do_rootfs`` so that 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
+:ref:`image <ref-classes-image>` class to the
+:ref:`rootfs-postcommands <ref-classes-rootfs*>` class. Functionally,
+however, they remain unchanged.
+
+.. _migration-2.1-removed-recipes:
+
+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
+   ":ref:`migration-guides/migration-2.1:adt removed`" section for more information.
+
+.. _migration-2.1-class-changes:
+
+Class Changes
+-------------
+
+The following classes have changed:
+
+-  ``autotools_stage``: Removed because the
+   :ref:`autotools <ref-classes-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
+   :ref:`image-live <ref-classes-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.
+
+.. _migration-2.1-build-system-ui-changes:
+
+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
+   ":ref:`toaster-manual/setup-and-use: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.
+
+.. _migration-2.1-adt-removed:
+
+ADT Removed
+-----------
+
+The Application Development Toolkit (ADT) has been removed because its
+functionality almost completely overlapped with the :ref:`standard
+SDK <sdk-manual/using:using the standard sdk>` and the
+:ref:`extensible SDK <sdk-manual/extensible:using the extensible sdk>`. For
+information on these SDKs and how to build and use them, see the
+:doc:`/sdk-manual/index` manual.
+
+.. note::
+
+   The Yocto Project Eclipse IDE Plug-in is still supported and is not
+   affected by this change.
+
+.. _migration-2.1-poky-reference-distribution-changes:
+
+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 :ref:`uninative <ref-classes-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.
+
+.. _migration-2.1-packaging-changes:
+
+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.
+
+.. _migration-2.1-tuning-file-changes:
+
+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.
+
+   .. note::
+
+      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.
+
+.. _migration-2.1-supporting-gobject-introspection:
+
+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
+":ref:`dev-manual/common-tasks:enabling gobject introspection support`"
+section in the Yocto Project Development Tasks Manual for more
+information.
+
+.. _migration-2.1-miscellaneous-changes:
+
+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
+   :ref:`ref-manual/system-requirements: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
+   :term:`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
+   :ref:`devtool modify <sdk-manual/extensible:use \`\`devtool modify\`\` to modify the source of an existing component>`
+   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.
+
+   .. note::
+
+      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.
+
+