From 43d07a285181e64c30d98d10ff93ef50391efe59 Mon Sep 17 00:00:00 2001 From: Nicolas Dechesne Date: Mon, 5 Oct 2020 16:30:32 +0200 Subject: sphinx: remove DocBook files The Yocto Project documentation was migrated to Sphinx. Let's remove the deprecated DocBook files. (From yocto-docs rev: 28fb0e63b2fbfd6426b00498bf2682bb53fdd862) Signed-off-by: Nicolas Dechesne Signed-off-by: Richard Purdie --- .../overview-manual/overview-manual-concepts.xml | 3235 -------------------- .../overview-manual-customization.xsl | 29 - .../overview-manual-development-environment.xml | 954 ------ .../overview-manual/overview-manual-intro.xml | 113 - .../overview-manual/overview-manual-style.css | 990 ------ .../overview-manual/overview-manual-yp-intro.xml | 1333 -------- documentation/overview-manual/overview-manual.xml | 130 - 7 files changed, 6784 deletions(-) delete mode 100644 documentation/overview-manual/overview-manual-concepts.xml delete mode 100644 documentation/overview-manual/overview-manual-customization.xsl delete mode 100644 documentation/overview-manual/overview-manual-development-environment.xml delete mode 100644 documentation/overview-manual/overview-manual-intro.xml delete mode 100644 documentation/overview-manual/overview-manual-style.css delete mode 100644 documentation/overview-manual/overview-manual-yp-intro.xml delete mode 100755 documentation/overview-manual/overview-manual.xml (limited to 'documentation/overview-manual') diff --git a/documentation/overview-manual/overview-manual-concepts.xml b/documentation/overview-manual/overview-manual-concepts.xml deleted file mode 100644 index 58b64bd269..0000000000 --- a/documentation/overview-manual/overview-manual-concepts.xml +++ /dev/null @@ -1,3235 +0,0 @@ - %poky; ] > - - - -Yocto Project Concepts - - - This chapter provides explanations for Yocto Project concepts that - go beyond the surface of "how-to" information and reference (or - look-up) material. - Concepts such as components, the - OpenEmbedded build system - workflow, cross-development toolchains, shared state cache, and so - forth are explained. - - -
- Yocto Project Components - - - The - BitBake - task executor together with various types of configuration files - form the - OpenEmbedded-Core. - This section overviews these components by describing their use and - how they interact. - - - - BitBake handles the parsing and execution of the data files. - The data itself is of various types: - - - Recipes: - Provides details about particular pieces of software. - - - Class Data: - Abstracts common build information (e.g. how to build a - Linux kernel). - - - Configuration Data: - Defines machine-specific settings, policy decisions, and - so forth. - Configuration data acts as the glue to bind everything - together. - - - - - - BitBake knows how to combine multiple data sources together and - refers to each data source as a layer. - For information on layers, see the - "Understanding and Creating Layers" - section of the Yocto Project Development Tasks Manual. - - - - Following are some brief details on these core components. - For additional information on how these components interact during - a build, see the - "OpenEmbedded Build System Concepts" - section. - - -
- BitBake - - - BitBake is the tool at the heart of the - OpenEmbedded build system - and is responsible for parsing the - Metadata, - generating a list of tasks from it, and then executing those - tasks. - - - - This section briefly introduces BitBake. - If you want more information on BitBake, see the - BitBake User Manual. - - - - To see a list of the options BitBake supports, use either of - the following commands: - - $ bitbake -h - $ bitbake --help - - - - - The most common usage for BitBake is - bitbake packagename, - where packagename is the name of the - package you want to build (referred to as the "target"). - The target often equates to the first part of a recipe's - filename (e.g. "foo" for a recipe named - foo_1.3.0-r0.bb). - So, to process the - matchbox-desktop_1.2.3.bb recipe file, you - might type the following: - - $ bitbake matchbox-desktop - - Several different versions of - matchbox-desktop might exist. - BitBake chooses the one selected by the distribution - configuration. - You can get more details about how BitBake chooses between - different target versions and providers in the - "Preferences" - section of the BitBake User Manual. - - - - BitBake also tries to execute any dependent tasks first. - So for example, before building - matchbox-desktop, BitBake would build a - cross compiler and glibc if they had not - already been built. - - - - A useful BitBake option to consider is the - -k or --continue - option. - This option instructs BitBake to try and continue processing - the job as long as possible even after encountering an error. - When an error occurs, the target that failed and those that - depend on it cannot be remade. - However, when you use this option other dependencies can - still be processed. - -
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- Recipes - - - Files that have the .bb suffix are - "recipes" files. - In general, a recipe contains information about a single piece - of software. - This information includes the location from which to download - the unaltered source, any source patches to be applied to that - source (if needed), which special configuration options to - apply, how to compile the source files, and how to package the - compiled output. - - - - The term "package" is sometimes used to refer to recipes. - However, since the word "package" is used for the packaged - output from the OpenEmbedded build system (i.e. - .ipk or .deb files), - this document avoids using the term "package" when referring - to recipes. - -
- -
- Classes - - - Class files (.bbclass) contain information - that is useful to share between recipes files. - An example is the - autotools - class, which contains common settings for any application that - Autotools uses. - The - "Classes" - chapter in the Yocto Project Reference Manual provides - details about classes and how to use them. - -
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- Configurations - - - The configuration files (.conf) define - various configuration variables that govern the OpenEmbedded - build process. - These files fall into several areas that define machine - configuration options, distribution configuration options, - compiler tuning options, general common configuration options, - and user configuration options in - conf/local.conf, which is found in the - Build Directory. - -
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- -
- Layers - - - Layers are repositories that contain related metadata (i.e. - sets of instructions) that tell the OpenEmbedded build system how - to build a target. - Yocto Project's - layer model - facilitates collaboration, sharing, customization, and reuse - within the Yocto Project development environment. - Layers logically separate information for your project. - For example, you can use a layer to hold all the configurations - for a particular piece of hardware. - Isolating hardware-specific configurations allows you to share - other metadata by using a different layer where that metadata - might be common across several pieces of hardware. - - - - Many layers exist that work in the Yocto Project development - environment. - The - Yocto Project Curated Layer Index - and - OpenEmbedded Layer Index - both contain layers from which you can use or leverage. - - - - By convention, layers in the Yocto Project follow a specific form. - Conforming to a known structure allows BitBake to make assumptions - during builds on where to find types of metadata. - You can find procedures and learn about tools (i.e. - bitbake-layers) for creating layers suitable - for the Yocto Project in the - "Understanding and Creating Layers" - section of the Yocto Project Development Tasks Manual. - -
- -
- OpenEmbedded Build System Concepts - - - This section takes a more detailed look inside the build - process used by the - OpenEmbedded build system, - which is the build system specific to the Yocto Project. - At the heart of the build system is BitBake, the task executor. - - - - The following diagram represents the high-level workflow of a - build. - The remainder of this section expands on the fundamental input, - output, process, and metadata logical blocks that make up the - workflow. - - - - - - - - In general, the build's workflow consists of several functional - areas: - - - User Configuration: - metadata you can use to control the build process. - - - Metadata Layers: - Various layers that provide software, machine, and - distro metadata. - - - Source Files: - Upstream releases, local projects, and SCMs. - - - Build System: - Processes under the control of - BitBake. - This block expands on how BitBake fetches source, applies - patches, completes compilation, analyzes output for package - generation, creates and tests packages, generates images, - and generates cross-development tools. - - - Package Feeds: - Directories containing output packages (RPM, DEB or IPK), - which are subsequently used in the construction of an - image or Software Development Kit (SDK), produced by the - build system. - These feeds can also be copied and shared using a web - server or other means to facilitate extending or updating - existing images on devices at runtime if runtime package - management is enabled. - - - Images: - Images produced by the workflow. - - - Application Development SDK: - Cross-development tools that are produced along with - an image or separately with BitBake. - - - - -
- User Configuration - - - User configuration helps define the build. - Through user configuration, you can tell BitBake the - target architecture for which you are building the image, - where to store downloaded source, and other build properties. - - - - The following figure shows an expanded representation of the - "User Configuration" box of the - general workflow figure: - - - - - - - - BitBake needs some basic configuration files in order to - complete a build. - These files are *.conf files. - The minimally necessary ones reside as example files in the - build/conf directory of the - Source Directory. - For simplicity, this section refers to the Source Directory as - the "Poky Directory." - - - - When you clone the - Poky - Git repository or you download and unpack a Yocto Project - release, you can set up the Source Directory to be named - anything you want. - For this discussion, the cloned repository uses the default - name poky. - - The Poky repository is primarily an aggregation of existing - repositories. - It is not a canonical upstream source. - - - - - The meta-poky layer inside Poky contains - a conf directory that has example - configuration files. - These example files are used as a basis for creating actual - configuration files when you source - &OE_INIT_FILE;, - which is the build environment script. - - - - Sourcing the build environment script creates a - Build Directory - if one does not already exist. - BitBake uses the Build Directory for all its work during - builds. - The Build Directory has a conf directory - that contains default versions of your - local.conf and - bblayers.conf configuration files. - These default configuration files are created only if versions - do not already exist in the Build Directory at the time you - source the build environment setup script. - - - - Because the Poky repository is fundamentally an aggregation of - existing repositories, some users might be familiar with - running the &OE_INIT_FILE; script - in the context of separate - OpenEmbedded-Core - and BitBake repositories rather than a single Poky repository. - This discussion assumes the script is executed from - within a cloned or unpacked version of Poky. - - - - Depending on where the script is sourced, different - sub-scripts are called to set up the Build Directory - (Yocto or OpenEmbedded). - Specifically, the script - scripts/oe-setup-builddir inside the - poky directory sets up the Build Directory and seeds the - directory (if necessary) with configuration files appropriate - for the Yocto Project development environment. - - The scripts/oe-setup-builddir script - uses the $TEMPLATECONF variable to - determine which sample configuration files to locate. - - - - - The local.conf file provides many - basic variables that define a build environment. - Here is a list of a few. - To see the default configurations in a - local.conf file created by the build - environment script, see the - local.conf.sample - in the meta-poky layer: - - - Target Machine Selection: - Controlled by the - MACHINE - variable. - - - Download Directory: - Controlled by the - DL_DIR - variable. - - - Shared State Directory: - Controlled by the - SSTATE_DIR - variable. - - - Build Output: - Controlled by the - TMPDIR - variable. - - - Distribution Policy: - Controlled by the - DISTRO - variable. - - - Packaging Format: - Controlled by the - PACKAGE_CLASSES - variable. - - - SDK Target Architecture: - Controlled by the - SDKMACHINE - variable. - - - Extra Image Packages: - Controlled by the - EXTRA_IMAGE_FEATURES - variable. - - - - Configurations set in the - conf/local.conf file can also be set - in the conf/site.conf and - conf/auto.conf configuration files. - - - - - The bblayers.conf file tells BitBake what - layers you want considered during the build. - By default, the layers listed in this file include layers - minimally needed by the build system. - However, you must manually add any custom layers you have - created. - You can find more information on working with the - bblayers.conf file in the - "Enabling Your Layer" - section in the Yocto Project Development Tasks Manual. - - - - The files site.conf and - auto.conf are not created by the - environment initialization script. - If you want the site.conf file, you - need to create that yourself. - The auto.conf file is typically created by - an autobuilder: - - - site.conf: - You can use the conf/site.conf - configuration file to configure multiple - build directories. - For example, suppose you had several build environments - and they shared some common features. - You can set these default build properties here. - A good example is perhaps the packaging format to use - through the - PACKAGE_CLASSES - variable. - - One useful scenario for using the - conf/site.conf file is to extend - your - BBPATH - variable to include the path to a - conf/site.conf. - Then, when BitBake looks for Metadata using - BBPATH, it finds the - conf/site.conf file and applies - your common configurations found in the file. - To override configurations in a particular build - directory, alter the similar configurations within - that build directory's - conf/local.conf file. - - - auto.conf: - The file is usually created and written to by - an autobuilder. - The settings put into the file are typically the - same as you would find in the - conf/local.conf or the - conf/site.conf files. - - - - - - You can edit all configuration files to further define - any particular build environment. - This process is represented by the "User Configuration Edits" - box in the figure. - - - - When you launch your build with the - bitbake target - command, BitBake sorts out the configurations to ultimately - define your build environment. - It is important to understand that the - OpenEmbedded build system - reads the configuration files in a specific order: - site.conf, auto.conf, - and local.conf. - And, the build system applies the normal assignment statement - rules as described in the - "Syntax and Operators" - chapter of the BitBake User Manual. - Because the files are parsed in a specific order, variable - assignments for the same variable could be affected. - For example, if the auto.conf file and - the local.conf set - variable1 to different values, - because the build system parses local.conf - after auto.conf, - variable1 is assigned the value from - the local.conf file. - -
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- Metadata, Machine Configuration, and Policy Configuration - - - The previous section described the user configurations that - define BitBake's global behavior. - This section takes a closer look at the layers the build system - uses to further control the build. - These layers provide Metadata for the software, machine, and - policies. - - - - In general, three types of layer input exists. - You can see them below the "User Configuration" box in the - general workflow figure: - - - Metadata (.bb + Patches): - Software layers containing user-supplied recipe files, - patches, and append files. - A good example of a software layer might be the - meta-qt5 - layer from the - OpenEmbedded Layer Index. - This layer is for version 5.0 of the popular - Qt - cross-platform application development framework for - desktop, embedded and mobile. - - - Machine BSP Configuration: - Board Support Package (BSP) layers (i.e. "BSP Layer" - in the following figure) providing machine-specific - configurations. - This type of information is specific to a particular - target architecture. - A good example of a BSP layer from the - Poky Reference Distribution - is the - meta-yocto-bsp - layer. - - - Policy Configuration: - Distribution Layers (i.e. "Distro Layer" in the - following figure) providing top-level or general - policies for the images or SDKs being built for a - particular distribution. - For example, in the Poky Reference Distribution the - distro layer is the - meta-poky - layer. - Within the distro layer is a - conf/distro directory that - contains distro configuration files (e.g. - poky.conf - that contain many policy configurations for the - Poky distribution. - - - - - - The following figure shows an expanded representation of - these three layers from the - general workflow figure: - - - - - - - - In general, all layers have a similar structure. - They all contain a licensing file - (e.g. COPYING.MIT) if the layer is to be - distributed, a README file as good - practice and especially if the layer is to be distributed, a - configuration directory, and recipe directories. - You can learn about the general structure for layers used with - the Yocto Project in the - "Creating Your Own Layer" - section in the Yocto Project Development Tasks Manual. - For a general discussion on layers and the many layers from - which you can draw, see the - "Layers" and - "The Yocto Project Layer Model" - sections both earlier in this manual. - - - - If you explored the previous links, you discovered some - areas where many layers that work with the Yocto Project - exist. - The - Source Repositories - also shows layers categorized under "Yocto Metadata Layers." - - Layers exist in the Yocto Project Source Repositories that - cannot be found in the OpenEmbedded Layer Index. - These layers are either deprecated or experimental - in nature. - - - - - BitBake uses the conf/bblayers.conf file, - which is part of the user configuration, to find what layers it - should be using as part of the build. - - -
- Distro Layer - - - The distribution layer provides policy configurations for - your distribution. - Best practices dictate that you isolate these types of - configurations into their own layer. - Settings you provide in - conf/distro/distro.conf override - similar settings that BitBake finds in your - conf/local.conf file in the Build - Directory. - - - - The following list provides some explanation and references - for what you typically find in the distribution layer: - - - classes: - Class files (.bbclass) hold - common functionality that can be shared among - recipes in the distribution. - When your recipes inherit a class, they take on the - settings and functions for that class. - You can read more about class files in the - "Classes" - chapter of the Yocto Reference Manual. - - - conf: - This area holds configuration files for the - layer (conf/layer.conf), - the distribution - (conf/distro/distro.conf), - and any distribution-wide include files. - - - recipes-*: - Recipes and append files that affect common - functionality across the distribution. - This area could include recipes and append files - to add distribution-specific configuration, - initialization scripts, custom image recipes, - and so forth. - Examples of recipes-* - directories are recipes-core - and recipes-extra. - Hierarchy and contents within a - recipes-* directory can vary. - Generally, these directories contain recipe files - (*.bb), recipe append files - (*.bbappend), directories - that are distro-specific for configuration files, - and so forth. - - - -
- -
- BSP Layer - - - The BSP Layer provides machine configurations that - target specific hardware. - Everything in this layer is specific to the machine for - which you are building the image or the SDK. - A common structure or form is defined for BSP layers. - You can learn more about this structure in the - Yocto Project Board Support Package (BSP) Developer's Guide. - - In order for a BSP layer to be considered compliant - with the Yocto Project, it must meet some structural - requirements. - - - - - The BSP Layer's configuration directory contains - configuration files for the machine - (conf/machine/machine.conf) - and, of course, the layer - (conf/layer.conf). - - - - The remainder of the layer is dedicated to specific recipes - by function: recipes-bsp, - recipes-core, - recipes-graphics, - recipes-kernel, and so forth. - Metadata can exist for multiple formfactors, graphics - support systems, and so forth. - - While the figure shows several - recipes-* directories, not all - these directories appear in all BSP layers. - - -
- -
- Software Layer - - - The software layer provides the Metadata for additional - software packages used during the build. - This layer does not include Metadata that is specific to - the distribution or the machine, which are found in their - respective layers. - - - - This layer contains any recipes, append files, and - patches, that your project needs. - -
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- Sources - - - In order for the OpenEmbedded build system to create an - image or any target, it must be able to access source files. - The - general workflow figure - represents source files using the "Upstream Project Releases", - "Local Projects", and "SCMs (optional)" boxes. - The figure represents mirrors, which also play a role in - locating source files, with the "Source Materials" box. - - - - The method by which source files are ultimately organized is - a function of the project. - For example, for released software, projects tend to use - tarballs or other archived files that can capture the - state of a release guaranteeing that it is statically - represented. - On the other hand, for a project that is more dynamic or - experimental in nature, a project might keep source files in a - repository controlled by a Source Control Manager (SCM) such as - Git. - Pulling source from a repository allows you to control - the point in the repository (the revision) from which you - want to build software. - Finally, a combination of the two might exist, which would - give the consumer a choice when deciding where to get - source files. - - - - BitBake uses the - SRC_URI - variable to point to source files regardless of their location. - Each recipe must have a SRC_URI variable - that points to the source. - - - - Another area that plays a significant role in where source - files come from is pointed to by the - DL_DIR - variable. - This area is a cache that can hold previously downloaded - source. - You can also instruct the OpenEmbedded build system to create - tarballs from Git repositories, which is not the default - behavior, and store them in the DL_DIR - by using the - BB_GENERATE_MIRROR_TARBALLS - variable. - - - - Judicious use of a DL_DIR directory can - save the build system a trip across the Internet when looking - for files. - A good method for using a download directory is to have - DL_DIR point to an area outside of your - Build Directory. - Doing so allows you to safely delete the Build Directory - if needed without fear of removing any downloaded source file. - - - - The remainder of this section provides a deeper look into the - source files and the mirrors. - Here is a more detailed look at the source file area of the - general workflow figure: - - - - - - -
- Upstream Project Releases - - - Upstream project releases exist anywhere in the form of an - archived file (e.g. tarball or zip file). - These files correspond to individual recipes. - For example, the figure uses specific releases each for - BusyBox, Qt, and Dbus. - An archive file can be for any released product that can be - built using a recipe. - -
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- Local Projects - - - Local projects are custom bits of software the user - provides. - These bits reside somewhere local to a project - perhaps - a directory into which the user checks in items (e.g. - a local directory containing a development source tree - used by the group). - - - - The canonical method through which to include a local - project is to use the - externalsrc - class to include that local project. - You use either the local.conf or a - recipe's append file to override or set the - recipe to point to the local directory on your disk to pull - in the whole source tree. - -
- -
- Source Control Managers (Optional) - - - Another place from which the build system can get source - files is with - fetchers - employing various Source Control Managers (SCMs) such as - Git or Subversion. - In such cases, a repository is cloned or checked out. - The - do_fetch - task inside BitBake uses - the SRC_URI - variable and the argument's prefix to determine the correct - fetcher module. - - For information on how to have the OpenEmbedded build - system generate tarballs for Git repositories and place - them in the - DL_DIR - directory, see the - BB_GENERATE_MIRROR_TARBALLS - variable in the Yocto Project Reference Manual. - - - - - When fetching a repository, BitBake uses the - SRCREV - variable to determine the specific revision from which to - build. - -
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- Source Mirror(s) - - - Two kinds of mirrors exist: pre-mirrors and regular - mirrors. - The - PREMIRRORS - and - MIRRORS - variables point to these, respectively. - BitBake checks pre-mirrors before looking upstream for any - source files. - Pre-mirrors are appropriate when you have a shared - directory that is not a directory defined by the - DL_DIR - variable. - A Pre-mirror typically points to a shared directory that is - local to your organization. - - - - Regular mirrors can be any site across the Internet - that is used as an alternative location for source - code should the primary site not be functioning for - some reason or another. - -
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- -
- Package Feeds - - - When the OpenEmbedded build system generates an image or an - SDK, it gets the packages from a package feed area located - in the - Build Directory. - The - general workflow figure - shows this package feeds area in the upper-right corner. - - - - This section looks a little closer into the package feeds - area used by the build system. - Here is a more detailed look at the area: - - - - - Package feeds are an intermediary step in the build process. - The OpenEmbedded build system provides classes to generate - different package types, and you specify which classes to - enable through the - PACKAGE_CLASSES - variable. - Before placing the packages into package feeds, - the build process validates them with generated output quality - assurance checks through the - insane - class. - - - - The package feed area resides in the Build Directory. - The directory the build system uses to temporarily store - packages is determined by a combination of variables and the - particular package manager in use. - See the "Package Feeds" box in the illustration and note the - information to the right of that area. - In particular, the following defines where package files are - kept: - - - DEPLOY_DIR: - Defined as tmp/deploy in the Build - Directory. - - - DEPLOY_DIR_*: - Depending on the package manager used, the package type - sub-folder. - Given RPM, IPK, or DEB packaging and tarball creation, - the - DEPLOY_DIR_RPM, - DEPLOY_DIR_IPK, - DEPLOY_DIR_DEB, - or - DEPLOY_DIR_TAR, - variables are used, respectively. - - - PACKAGE_ARCH: - Defines architecture-specific sub-folders. - For example, packages could exist for the i586 or - qemux86 architectures. - - - - - - BitBake uses the - do_package_write_* - tasks to generate packages and place them into the package - holding area (e.g. do_package_write_ipk - for IPK packages). - See the - "do_package_write_deb", - "do_package_write_ipk", - "do_package_write_rpm", - and - "do_package_write_tar" - sections in the Yocto Project Reference Manual - for additional information. - As an example, consider a scenario where an IPK packaging - manager is being used and package architecture support for - both i586 and qemux86 exist. - Packages for the i586 architecture are placed in - build/tmp/deploy/ipk/i586, while packages - for the qemux86 architecture are placed in - build/tmp/deploy/ipk/qemux86. - -
- -
- BitBake - - - The OpenEmbedded build system uses - BitBake - to produce images and Software Development Kits (SDKs). - You can see from the - general workflow figure, - the BitBake area consists of several functional areas. - This section takes a closer look at each of those areas. - - Separate documentation exists for the BitBake tool. - See the - BitBake User Manual - for reference material on BitBake. - - - -
- Source Fetching - - - The first stages of building a recipe are to fetch and - unpack the source code: - - - - - The - do_fetch - and - do_unpack - tasks fetch the source files and unpack them into the - Build Directory. - - For every local file (e.g. file://) - that is part of a recipe's - SRC_URI - statement, the OpenEmbedded build system takes a - checksum of the file for the recipe and inserts the - checksum into the signature for the - do_fetch task. - If any local file has been modified, the - do_fetch task and all tasks that - depend on it are re-executed. - - By default, everything is accomplished in the Build - Directory, which has a defined structure. - For additional general information on the Build Directory, - see the - "build/" - section in the Yocto Project Reference Manual. - - - - Each recipe has an area in the Build Directory where the - unpacked source code resides. - The - S - variable points to this area for a recipe's unpacked source - code. - The name of that directory for any given recipe is defined - from several different variables. - The preceding figure and the following list describe - the Build Directory's hierarchy: - - - TMPDIR: - The base directory where the OpenEmbedded build - system performs all its work during the build. - The default base directory is the - tmp directory. - - - PACKAGE_ARCH: - The architecture of the built package or packages. - Depending on the eventual destination of the - package or packages (i.e. machine architecture, - build host, - SDK, or specific machine), - PACKAGE_ARCH varies. - See the variable's description for details. - - - TARGET_OS: - The operating system of the target device. - A typical value would be "linux" (e.g. - "qemux86-poky-linux"). - - - PN: - The name of the recipe used to build the package. - This variable can have multiple meanings. - However, when used in the context of input files, - PN represents the the name - of the recipe. - - - WORKDIR: - The location where the OpenEmbedded build system - builds a recipe (i.e. does the work to create the - package). - - - PV: - The version of the recipe used to build the - package. - - - PR: - The revision of the recipe used to build the - package. - - - - - S: - Contains the unpacked source files for a given - recipe. - - - BPN: - The name of the recipe used to build the - package. - The BPN variable is - a version of the PN - variable but with common prefixes and - suffixes removed. - - - PV: - The version of the recipe used to build the - package. - - - - - - In the previous figure, notice that two sample - hierarchies exist: one based on package architecture (i.e. - PACKAGE_ARCH) and one based on a - machine (i.e. MACHINE). - The underlying structures are identical. - The differentiator being what the OpenEmbedded build - system is using as a build target (e.g. general - architecture, a build host, an SDK, or a specific - machine). - - -
- -
- Patching - - - Once source code is fetched and unpacked, BitBake locates - patch files and applies them to the source files: - - - - - The - do_patch - task uses a recipe's - SRC_URI - statements and the - FILESPATH - variable to locate applicable patch files. - - - - Default processing for patch files assumes the files have - either *.patch or - *.diff file types. - You can use SRC_URI parameters to - change the way the build system recognizes patch files. - See the - do_patch - task for more information. - - - - BitBake finds and applies multiple patches for a single - recipe in the order in which it locates the patches. - The FILESPATH variable defines the - default set of directories that the build system uses to - search for patch files. - Once found, patches are applied to the recipe's source - files, which are located in the - S - directory. - - - - For more information on how the source directories are - created, see the - "Source Fetching" - section. - For more information on how to create patches and how the - build system processes patches, see the - "Patching Code" - section in the Yocto Project Development Tasks Manual. - You can also see the - "Use devtool modify to Modify the Source of an Existing Component" - section in the Yocto Project Application Development and - the Extensible Software Development Kit (SDK) manual and - the - "Using Traditional Kernel Development to Patch the Kernel" - section in the Yocto Project Linux Kernel Development - Manual. - -
- -
- Configuration, Compilation, and Staging - - - After source code is patched, BitBake executes tasks that - configure and compile the source code. - Once compilation occurs, the files are copied to a holding - area (staged) in preparation for packaging: - - - - - This step in the build process consists of the following - tasks: - - - do_prepare_recipe_sysroot: - This task sets up the two sysroots in - ${WORKDIR} - (i.e. recipe-sysroot and - recipe-sysroot-native) so that - during the packaging phase the sysroots can contain - the contents of the - do_populate_sysroot - tasks of the recipes on which the recipe - containing the tasks depends. - A sysroot exists for both the target and for the - native binaries, which run on the host system. - - - do_configure: - This task configures the source by enabling and - disabling any build-time and configuration options - for the software being built. - Configurations can come from the recipe itself as - well as from an inherited class. - Additionally, the software itself might configure - itself depending on the target for which it is - being built. - - The configurations handled by the - do_configure - task are specific to configurations for the source - code being built by the recipe. - - If you are using the - autotools - class, you can add additional configuration options - by using the - EXTRA_OECONF - or - PACKAGECONFIG_CONFARGS - variables. - For information on how this variable works within - that class, see the - autotools - class - here. - - - do_compile: - Once a configuration task has been satisfied, - BitBake compiles the source using the - do_compile - task. - Compilation occurs in the directory pointed to by - the - B - variable. - Realize that the B directory - is, by default, the same as the - S - directory. - - - do_install: - After compilation completes, BitBake executes the - do_install - task. - This task copies files from the - B directory and places them - in a holding area pointed to by the - D - variable. - Packaging occurs later using files from this - holding directory. - - - -
- -
- Package Splitting - - - After source code is configured, compiled, and staged, the - build system analyzes the results and splits the output - into packages: - - - - - The - do_package - and - do_packagedata - tasks combine to analyze the files found in the - D - directory and split them into subsets based on available - packages and files. - Analysis involves the following as well as other items: - splitting out debugging symbols, looking at shared library - dependencies between packages, and looking at package - relationships. - - - - The do_packagedata task creates - package metadata based on the analysis such that the - build system can generate the final packages. - The - do_populate_sysroot - task stages (copies) a subset of the files installed by - the - do_install - task into the appropriate sysroot. - Working, staged, and intermediate results of the analysis - and package splitting process use several areas: - - - PKGD: - The destination directory - (i.e. package) for packages - before they are split into individual packages. - - - PKGDESTWORK: - A temporary work area (i.e. - pkgdata) used by the - do_package task to save - package metadata. - - - PKGDEST: - The parent directory (i.e. - packages-split) for packages - after they have been split. - - - PKGDATA_DIR: - A shared, global-state directory that holds - packaging metadata generated during the packaging - process. - The packaging process copies metadata from - PKGDESTWORK to the - PKGDATA_DIR area where it - becomes globally available. - - - STAGING_DIR_HOST: - The path for the sysroot for the system on which - a component is built to run (i.e. - recipe-sysroot). - - - STAGING_DIR_NATIVE: - The path for the sysroot used when building - components for the build host (i.e. - recipe-sysroot-native). - - - STAGING_DIR_TARGET: - The path for the sysroot used when a component that - is built to execute on a system and it generates - code for yet another machine (e.g. cross-canadian - recipes). - - - The - FILES - variable defines the files that go into each package in - PACKAGES. - If you want details on how this is accomplished, you can - look at - package.bbclass. - - - - Depending on the type of packages being created (RPM, DEB, - or IPK), the - do_package_write_* - task creates the actual packages and places them in the - Package Feed area, which is - ${TMPDIR}/deploy. - You can see the - "Package Feeds" - section for more detail on that part of the build process. - - Support for creating feeds directly from the - deploy/* directories does not - exist. - Creating such feeds usually requires some kind of feed - maintenance mechanism that would upload the new - packages into an official package feed (e.g. the - Ångström distribution). - This functionality is highly distribution-specific - and thus is not provided out of the box. - - -
- -
- Image Generation - - - Once packages are split and stored in the Package Feeds - area, the build system uses BitBake to generate the root - filesystem image: - - - - - The image generation process consists of several stages and - depends on several tasks and variables. - The - do_rootfs - task creates the root filesystem (file and directory - structure) for an image. - This task uses several key variables to help create the - list of packages to actually install: - - - IMAGE_INSTALL: - Lists out the base set of packages from which to - install from the Package Feeds area. - - - PACKAGE_EXCLUDE: - Specifies packages that should not be installed - into the image. - - - IMAGE_FEATURES: - Specifies features to include in the image. - Most of these features map to additional packages - for installation. - - - PACKAGE_CLASSES: - Specifies the package backend (e.g. RPM, DEB, or - IPK) to use and consequently helps determine where - to locate packages within the Package Feeds area. - - - IMAGE_LINGUAS: - Determines the language(s) for which additional - language support packages are installed. - - - PACKAGE_INSTALL: - The final list of packages passed to the package - manager for installation into the image. - - - - - - With - IMAGE_ROOTFS - pointing to the location of the filesystem under - construction and the PACKAGE_INSTALL - variable providing the final list of packages to install, - the root file system is created. - - - - Package installation is under control of the package - manager (e.g. dnf/rpm, opkg, or apt/dpkg) regardless of - whether or not package management is enabled for the - target. - At the end of the process, if package management is not - enabled for the target, the package manager's data files - are deleted from the root filesystem. - As part of the final stage of package installation, - post installation scripts that are part of the packages - are run. - Any scripts that fail to run on the build host are run on - the target when the target system is first booted. - If you are using a - read-only root filesystem, - all the post installation scripts must succeed on the - build host during the package installation phase since the - root filesystem on the target is read-only. - - - - The final stages of the do_rootfs task - handle post processing. - Post processing includes creation of a manifest file and - optimizations. - - - - The manifest file (.manifest) resides - in the same directory as the root filesystem image. - This file lists out, line-by-line, the installed packages. - The manifest file is useful for the - testimage - class, for example, to determine whether or not to run - specific tests. - See the - IMAGE_MANIFEST - variable for additional information. - - - - Optimizing processes that are run across the image include - mklibs, prelink, - and any other post-processing commands as defined by the - ROOTFS_POSTPROCESS_COMMAND - variable. - The mklibs process optimizes the size - of the libraries, while the prelink - process optimizes the dynamic linking of shared libraries - to reduce start up time of executables. - - - - After the root filesystem is built, processing begins on - the image through the - do_image - task. - The build system runs any pre-processing commands as - defined by the - IMAGE_PREPROCESS_COMMAND - variable. - This variable specifies a list of functions to call before - the build system creates the final image output files. - - - - The build system dynamically creates - do_image_* tasks as needed, based - on the image types specified in the - IMAGE_FSTYPES - variable. - The process turns everything into an image file or a set of - image files and can compress the root filesystem image to - reduce the overall size of the image. - The formats used for the root filesystem depend on the - IMAGE_FSTYPES variable. - Compression depends on whether the formats support - compression. - - - - As an example, a dynamically created task when creating a - particular image type would - take the following form: - - do_image_type - - So, if the type as specified by - the IMAGE_FSTYPES were - ext4, the dynamically generated task - would be as follows: - - do_image_ext4 - - - - - The final task involved in image creation is the - do_image_complete - task. - This task completes the image by applying any image - post processing as defined through the - IMAGE_POSTPROCESS_COMMAND - variable. - The variable specifies a list of functions to call once the - build system has created the final image output files. - - The entire image generation process is run under - Pseudo. - Running under Pseudo ensures that the files in the - root filesystem have correct ownership. - - -
- -
- SDK Generation - - - The OpenEmbedded build system uses BitBake to generate the - Software Development Kit (SDK) installer scripts for both - the standard SDK and the extensible SDK (eSDK): - - - - - - For more information on the cross-development toolchain - generation, see the - "Cross-Development Toolchain Generation" - section. - For information on advantages gained when building a - cross-development toolchain using the - do_populate_sdk - task, see the - "Building an SDK Installer" - section in the Yocto Project Application Development - and the Extensible Software Development Kit (eSDK) - manual. - - - - - Like image generation, the SDK script process consists of - several stages and depends on many variables. - The - do_populate_sdk - and - do_populate_sdk_ext - tasks use these key variables to help create the list of - packages to actually install. - For information on the variables listed in the figure, - see the - "Application Development SDK" - section. - - - - The do_populate_sdk task helps create - the standard SDK and handles two parts: a target part and a - host part. - The target part is the part built for the target hardware - and includes libraries and headers. - The host part is the part of the SDK that runs on the - SDKMACHINE. - - - - The do_populate_sdk_ext task helps - create the extensible SDK and handles host and target parts - differently than its counter part does for the standard SDK. - For the extensible SDK, the task encapsulates the build - system, which includes everything needed (host and target) - for the SDK. - - - - Regardless of the type of SDK being constructed, the - tasks perform some cleanup after which a cross-development - environment setup script and any needed configuration files - are created. - The final output is the Cross-development - toolchain installation script (.sh - file), which includes the environment setup script. - -
- -
- Stamp Files and the Rerunning of Tasks - - - For each task that completes successfully, BitBake writes a - stamp file into the - STAMPS_DIR - directory. - The beginning of the stamp file's filename is determined - by the - STAMP - variable, and the end of the name consists of the task's - name and current - input checksum. - - This naming scheme assumes that - BB_SIGNATURE_HANDLER - is "OEBasicHash", which is almost always the case in - current OpenEmbedded. - - To determine if a task needs to be rerun, BitBake checks - if a stamp file with a matching input checksum exists - for the task. - If such a stamp file exists, the task's output is - assumed to exist and still be valid. - If the file does not exist, the task is rerun. - - The stamp mechanism is more general than the - shared state (sstate) cache mechanism described in the - "Setscene Tasks and Shared State" - section. - BitBake avoids rerunning any task that has a valid - stamp file, not just tasks that can be accelerated - through the sstate cache. - - However, you should realize that stamp files only - serve as a marker that some work has been done and that - these files do not record task output. - The actual task output would usually be somewhere in - TMPDIR - (e.g. in some recipe's - WORKDIR.) - What the sstate cache mechanism adds is a way to cache - task output that can then be shared between build - machines. - - Since STAMPS_DIR is usually a - subdirectory of TMPDIR, removing - TMPDIR will also remove - STAMPS_DIR, which means tasks will - properly be rerun to repopulate - TMPDIR. - - - - If you want some task to always be considered "out of - date", you can mark it with the - nostamp - varflag. - If some other task depends on such a task, then that - task will also always be considered out of date, which - might not be what you want. - - - - For details on how to view information about a task's - signature, see the - "Viewing Task Variable Dependencies" - section in the Yocto Project Development Tasks Manual. - -
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- Setscene Tasks and Shared State - - - The description of tasks so far assumes that BitBake needs - to build everything and no available prebuilt objects - exist. - BitBake does support skipping tasks if prebuilt objects are - available. - These objects are usually made available in the form of a - shared state (sstate) cache. - - For information on variables affecting sstate, see the - SSTATE_DIR - and - SSTATE_MIRRORS - variables. - - - - - The idea of a setscene task (i.e - do_taskname_setscene) - is a version of the task where - instead of building something, BitBake can skip to the end - result and simply place a set of files into specific - locations as needed. - In some cases, it makes sense to have a setscene task - variant (e.g. generating package files in the - do_package_write_* - task). - In other cases, it does not make sense (e.g. a - do_patch - task or a - do_unpack - task) since the work involved would be equal to or greater - than the underlying task. - - - - In the build system, the common tasks that have setscene - variants are - do_package, - do_package_write_*, - do_deploy, - do_packagedata, - and - do_populate_sysroot. - Notice that these tasks represent most of the tasks whose - output is an end result. - - - - The build system has knowledge of the relationship between - these tasks and other preceding tasks. - For example, if BitBake runs - do_populate_sysroot_setscene for - something, it does not make sense to run any of the - do_fetch, - do_unpack, - do_patch, - do_configure, - do_compile, and - do_install tasks. - However, if do_package needs to be - run, BitBake needs to run those other tasks. - - - - It becomes more complicated if everything can come - from an sstate cache because some objects are simply - not required at all. - For example, you do not need a compiler or native tools, - such as quilt, if nothing exists to compile or patch. - If the do_package_write_* packages - are available from sstate, BitBake does not need the - do_package task data. - - - - To handle all these complexities, BitBake runs in two - phases. - The first is the "setscene" stage. - During this stage, BitBake first checks the sstate cache - for any targets it is planning to build. - BitBake does a fast check to see if the object exists - rather than a complete download. - If nothing exists, the second phase, which is the setscene - stage, completes and the main build proceeds. - - - - If objects are found in the sstate cache, the build system - works backwards from the end targets specified by the user. - For example, if an image is being built, the build system - first looks for the packages needed for that image and the - tools needed to construct an image. - If those are available, the compiler is not needed. - Thus, the compiler is not even downloaded. - If something was found to be unavailable, or the - download or setscene task fails, the build system then - tries to install dependencies, such as the compiler, from - the cache. - - - - The availability of objects in the sstate cache is - handled by the function specified by the - BB_HASHCHECK_FUNCTION - variable and returns a list of available objects. - The function specified by the - BB_SETSCENE_DEPVALID - variable is the function that determines whether a given - dependency needs to be followed, and whether for any given - relationship the function needs to be passed. - The function returns a True or False value. - -
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- -
- Images - - - The images produced by the build system are compressed forms - of the root filesystem and are ready to boot on a target - device. - You can see from the - general workflow figure - that BitBake output, in part, consists of images. - This section takes a closer look at this output: - - - - - For a list of example images that the Yocto Project provides, - see the - "Images" - chapter in the Yocto Project Reference Manual. - - - - The build process writes images out to the - Build Directory - inside the - tmp/deploy/images/machine/ - folder as shown in the figure. - This folder contains any files expected to be loaded on the - target device. - The - DEPLOY_DIR - variable points to the deploy directory, - while the - DEPLOY_DIR_IMAGE - variable points to the appropriate directory containing images - for the current configuration. - - - kernel-image: - A kernel binary file. - The - KERNEL_IMAGETYPE - variable determines the naming scheme for the - kernel image file. - Depending on this variable, the file could begin with - a variety of naming strings. - The - deploy/images/machine - directory can contain multiple image files for the - machine. - - - root-filesystem-image: - Root filesystems for the target device (e.g. - *.ext3 or - *.bz2 files). - The - IMAGE_FSTYPES - variable determines the root filesystem image type. - The - deploy/images/machine - directory can contain multiple root filesystems for the - machine. - - - kernel-modules: - Tarballs that contain all the modules built for the - kernel. - Kernel module tarballs exist for legacy purposes and - can be suppressed by setting the - MODULE_TARBALL_DEPLOY - variable to "0". - The - deploy/images/machine - directory can contain multiple kernel module tarballs - for the machine. - - - bootloaders: - If applicable to the target machine, bootloaders - supporting the image. - The deploy/images/machine - directory can contain multiple bootloaders for the - machine. - - - symlinks: - The - deploy/images/machine - folder contains a symbolic link that points to the - most recently built file for each machine. - These links might be useful for external scripts that - need to obtain the latest version of each file. - - - -
- -
- Application Development SDK - - - In the - general workflow figure, - the output labeled "Application Development SDK" represents an - SDK. - The SDK generation process differs depending on whether you - build an extensible SDK (e.g. - bitbake -c populate_sdk_ext imagename) - or a standard SDK (e.g. - bitbake -c populate_sdk imagename). - This section takes a closer look at this output: - - - - - The specific form of this output is a set of files that - includes a self-extracting SDK installer - (*.sh), host and target manifest files, - and files used for SDK testing. - When the SDK installer file is run, it installs the SDK. - The SDK consists of a cross-development toolchain, a set of - libraries and headers, and an SDK environment setup script. - Running this installer essentially sets up your - cross-development environment. - You can think of the cross-toolchain as the "host" - part because it runs on the SDK machine. - You can think of the libraries and headers as the "target" - part because they are built for the target hardware. - The environment setup script is added so that you can - initialize the environment before using the tools. - - - Notes - - - The Yocto Project supports several methods by which - you can set up this cross-development environment. - These methods include downloading pre-built SDK - installers or building and installing your own SDK - installer. - - - For background information on cross-development - toolchains in the Yocto Project development - environment, see the - "Cross-Development Toolchain Generation" - section. - - - For information on setting up a cross-development - environment, see the - Yocto Project Application Development and the Extensible Software Development Kit (eSDK) - manual. - - - - - - All the output files for an SDK are written to the - deploy/sdk folder inside the - Build Directory - as shown in the previous figure. - Depending on the type of SDK, several variables exist that help - configure these files. - The following list shows the variables associated with an - extensible SDK: - - - DEPLOY_DIR: - Points to the deploy directory. - - - SDK_EXT_TYPE: - Controls whether or not shared state artifacts are - copied into the extensible SDK. - By default, all required shared state artifacts are - copied into the SDK. - - - SDK_INCLUDE_PKGDATA: - Specifies whether or not packagedata is included in the - extensible SDK for all recipes in the "world" target. - - - SDK_INCLUDE_TOOLCHAIN: - Specifies whether or not the toolchain is included - when building the extensible SDK. - - - SDK_LOCAL_CONF_WHITELIST: - A list of variables allowed through from the build - system configuration into the extensible SDK - configuration. - - - SDK_LOCAL_CONF_BLACKLIST: - A list of variables not allowed through from the build - system configuration into the extensible SDK - configuration. - - - SDK_INHERIT_BLACKLIST: - A list of classes to remove from the - INHERIT - value globally within the extensible SDK configuration. - - - This next list, shows the variables associated with a standard - SDK: - - - DEPLOY_DIR: - Points to the deploy directory. - - - SDKMACHINE: - Specifies the architecture of the machine on which the - cross-development tools are run to create packages for - the target hardware. - - - SDKIMAGE_FEATURES: - Lists the features to include in the "target" part - of the SDK. - - - TOOLCHAIN_HOST_TASK: - Lists packages that make up the host part of the SDK - (i.e. the part that runs on the - SDKMACHINE). - When you use - bitbake -c populate_sdk imagename - to create the SDK, a set of default packages apply. - This variable allows you to add more packages. - - - TOOLCHAIN_TARGET_TASK: - Lists packages that make up the target part of the SDK - (i.e. the part built for the target hardware). - - - SDKPATH: - Defines the default SDK installation path offered by - the installation script. - - - SDK_HOST_MANIFEST: - Lists all the installed packages that make up the host - part of the SDK. - This variable also plays a minor role for extensible - SDK development as well. - However, it is mainly used for the standard SDK. - - - SDK_TARGET_MANIFEST: - Lists all the installed packages that make up the - target part of the SDK. - This variable also plays a minor role for extensible - SDK development as well. - However, it is mainly used for the standard SDK. - - - -
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- -
- Cross-Development Toolchain Generation - - - The Yocto Project does most of the work for you when it comes to - creating - cross-development toolchains. - This section provides some technical background on how - cross-development toolchains are created and used. - For more information on toolchains, you can also see the - Yocto Project Application Development and the Extensible Software Development Kit (eSDK) - manual. - - - - In the Yocto Project development environment, cross-development - toolchains are used to build images and applications that run - on the target hardware. - With just a few commands, the OpenEmbedded build system creates - these necessary toolchains for you. - - - - The following figure shows a high-level build environment regarding - toolchain construction and use. - - - - - - - - Most of the work occurs on the Build Host. - This is the machine used to build images and generally work within - the the Yocto Project environment. - When you run - BitBake - to create an image, the OpenEmbedded build system - uses the host gcc compiler to bootstrap a - cross-compiler named gcc-cross. - The gcc-cross compiler is what BitBake uses to - compile source files when creating the target image. - You can think of gcc-cross simply as an - automatically generated cross-compiler that is used internally - within BitBake only. - - The extensible SDK does not use - gcc-cross-canadian since this SDK - ships a copy of the OpenEmbedded build system and the sysroot - within it contains gcc-cross. - - - - - The chain of events that occurs when gcc-cross is - bootstrapped is as follows: - - gcc -> binutils-cross -> gcc-cross-initial -> linux-libc-headers -> glibc-initial -> glibc -> gcc-cross -> gcc-runtime - - - - gcc: - The build host's GNU Compiler Collection (GCC). - - - binutils-cross: - The bare minimum binary utilities needed in order to run - the gcc-cross-initial phase of the - bootstrap operation. - - - gcc-cross-initial: - An early stage of the bootstrap process for creating - the cross-compiler. - This stage builds enough of the gcc-cross, - the C library, and other pieces needed to finish building the - final cross-compiler in later stages. - This tool is a "native" package (i.e. it is designed to run on - the build host). - - - linux-libc-headers: - Headers needed for the cross-compiler. - - - glibc-initial: - An initial version of the Embedded GNU C Library - (GLIBC) needed to bootstrap glibc. - - - glibc: - The GNU C Library. - - - gcc-cross: - The final stage of the bootstrap process for the - cross-compiler. - This stage results in the actual cross-compiler that - BitBake uses when it builds an image for a targeted - device. - - If you are replacing this cross compiler toolchain - with a custom version, you must replace - gcc-cross. - - This tool is also a "native" package (i.e. it is - designed to run on the build host). - - - gcc-runtime: - Runtime libraries resulting from the toolchain bootstrapping - process. - This tool produces a binary that consists of the - runtime libraries need for the targeted device. - - - - - - You can use the OpenEmbedded build system to build an installer for - the relocatable SDK used to develop applications. - When you run the installer, it installs the toolchain, which - contains the development tools (e.g., - gcc-cross-canadian, - binutils-cross-canadian, and other - nativesdk-* tools), - which are tools native to the SDK (i.e. native to - SDK_ARCH), - you need to cross-compile and test your software. - The figure shows the commands you use to easily build out this - toolchain. - This cross-development toolchain is built to execute on the - SDKMACHINE, - which might or might not be the same - machine as the Build Host. - - If your target architecture is supported by the Yocto Project, - you can take advantage of pre-built images that ship with the - Yocto Project and already contain cross-development toolchain - installers. - - - - - Here is the bootstrap process for the relocatable toolchain: - - gcc -> binutils-crosssdk -> gcc-crosssdk-initial -> linux-libc-headers -> - glibc-initial -> nativesdk-glibc -> gcc-crosssdk -> gcc-cross-canadian - - - - gcc: - The build host's GNU Compiler Collection (GCC). - - - binutils-crosssdk: - The bare minimum binary utilities needed in order to run - the gcc-crosssdk-initial phase of the - bootstrap operation. - - - gcc-crosssdk-initial: - An early stage of the bootstrap process for creating - the cross-compiler. - This stage builds enough of the - gcc-crosssdk and supporting pieces so that - the final stage of the bootstrap process can produce the - finished cross-compiler. - This tool is a "native" binary that runs on the build host. - - - linux-libc-headers: - Headers needed for the cross-compiler. - - - glibc-initial: - An initial version of the Embedded GLIBC needed to bootstrap - nativesdk-glibc. - - - nativesdk-glibc: - The Embedded GLIBC needed to bootstrap the - gcc-crosssdk. - - - gcc-crosssdk: - The final stage of the bootstrap process for the - relocatable cross-compiler. - The gcc-crosssdk is a transitory - compiler and never leaves the build host. - Its purpose is to help in the bootstrap process to create - the eventual gcc-cross-canadian - compiler, which is relocatable. - This tool is also a "native" package (i.e. it is - designed to run on the build host). - - - gcc-cross-canadian: - The final relocatable cross-compiler. - When run on the - SDKMACHINE, - this tool - produces executable code that runs on the target device. - Only one cross-canadian compiler is produced per architecture - since they can be targeted at different processor optimizations - using configurations passed to the compiler through the - compile commands. - This circumvents the need for multiple compilers and thus - reduces the size of the toolchains. - - - - - - For information on advantages gained when building a - cross-development toolchain installer, see the - "Building an SDK Installer" - appendix in the Yocto Project Application Development and the - Extensible Software Development Kit (eSDK) manual. - -
- -
- Shared State Cache - - - By design, the OpenEmbedded build system builds everything from - scratch unless - BitBake - can determine that parts do not need to be rebuilt. - Fundamentally, building from scratch is attractive as it means all - parts are built fresh and no possibility of stale data exists that - can cause problems. - When developers hit problems, they typically default back to - building from scratch so they have a know state from the - start. - - - - Building an image from scratch is both an advantage and a - disadvantage to the process. - As mentioned in the previous paragraph, building from scratch - ensures that everything is current and starts from a known state. - However, building from scratch also takes much longer as it - generally means rebuilding things that do not necessarily need - to be rebuilt. - - - - The Yocto Project implements shared state code that supports - incremental builds. - The implementation of the shared state code answers the following - questions that were fundamental roadblocks within the OpenEmbedded - incremental build support system: - - - What pieces of the system have changed and what pieces have - not changed? - - - How are changed pieces of software removed and replaced? - - - How are pre-built components that do not need to be rebuilt - from scratch used when they are available? - - - - - - For the first question, the build system detects changes in the - "inputs" to a given task by creating a checksum (or signature) of - the task's inputs. - If the checksum changes, the system assumes the inputs have changed - and the task needs to be rerun. - For the second question, the shared state (sstate) code tracks - which tasks add which output to the build process. - This means the output from a given task can be removed, upgraded - or otherwise manipulated. - The third question is partly addressed by the solution for the - second question assuming the build system can fetch the sstate - objects from remote locations and install them if they are deemed - to be valid. - Notes - - - The build system does not maintain - PR - information as part of the shared state packages. - Consequently, considerations exist that affect - maintaining shared state feeds. - For information on how the build system works with - packages and can track incrementing - PR information, see the - "Automatically Incrementing a Binary Package Revision Number" - section in the Yocto Project Development Tasks Manual. - - - The code in the build system that supports incremental - builds is not simple code. - For techniques that help you work around issues related - to shared state code, see the - "Viewing Metadata Used to Create the Input Signature of a Shared State Task" - and - "Invalidating Shared State to Force a Task to Run" - sections both in the Yocto Project Development Tasks - Manual. - - - - - - - The rest of this section goes into detail about the overall - incremental build architecture, the checksums (signatures), and - shared state. - - -
- Overall Architecture - - - When determining what parts of the system need to be built, - BitBake works on a per-task basis rather than a per-recipe - basis. - You might wonder why using a per-task basis is preferred over - a per-recipe basis. - To help explain, consider having the IPK packaging backend - enabled and then switching to DEB. - In this case, the - do_install - and - do_package - task outputs are still valid. - However, with a per-recipe approach, the build would not - include the .deb files. - Consequently, you would have to invalidate the whole build and - rerun it. - Rerunning everything is not the best solution. - Also, in this case, the core must be "taught" much about - specific tasks. - This methodology does not scale well and does not allow users - to easily add new tasks in layers or as external recipes - without touching the packaged-staging core. - -
- -
- Checksums (Signatures) - - - The shared state code uses a checksum, which is a unique - signature of a task's inputs, to determine if a task needs to - be run again. - Because it is a change in a task's inputs that triggers a - rerun, the process needs to detect all the inputs to a given - task. - For shell tasks, this turns out to be fairly easy because - the build process generates a "run" shell script for each task - and it is possible to create a checksum that gives you a good - idea of when the task's data changes. - - - - To complicate the problem, there are things that should not be - included in the checksum. - First, there is the actual specific build path of a given - task - the - WORKDIR. - It does not matter if the work directory changes because it - should not affect the output for target packages. - Also, the build process has the objective of making native - or cross packages relocatable. - - Both native and cross packages run on the - build host. - However, cross packages generate output for the target - architecture. - - The checksum therefore needs to exclude - WORKDIR. - The simplistic approach for excluding the work directory is to - set WORKDIR to some fixed value and - create the checksum for the "run" script. - - - - Another problem results from the "run" scripts containing - functions that might or might not get called. - The incremental build solution contains code that figures out - dependencies between shell functions. - This code is used to prune the "run" scripts down to the - minimum set, thereby alleviating this problem and making the - "run" scripts much more readable as a bonus. - - - - So far, solutions for shell scripts exist. - What about Python tasks? - The same approach applies even though these tasks are more - difficult. - The process needs to figure out what variables a Python - function accesses and what functions it calls. - Again, the incremental build solution contains code that first - figures out the variable and function dependencies, and then - creates a checksum for the data used as the input to the task. - - - - Like the WORKDIR case, situations exist - where dependencies should be ignored. - For these situations, you can instruct the build process to - ignore a dependency by using a line like the following: - - PACKAGE_ARCHS[vardepsexclude] = "MACHINE" - - This example ensures that the - PACKAGE_ARCHS - variable does not depend on the value of - MACHINE, - even if it does reference it. - - - - Equally, there are cases where you need to add dependencies - BitBake is not able to find. - You can accomplish this by using a line like the following: - - PACKAGE_ARCHS[vardeps] = "MACHINE" - - This example explicitly adds the MACHINE - variable as a dependency for - PACKAGE_ARCHS. - - - - As an example, consider a case with in-line Python where - BitBake is not able to figure out dependencies. - When running in debug mode (i.e. using - -DDD), BitBake produces output when it - discovers something for which it cannot figure out dependencies. - The Yocto Project team has currently not managed to cover - those dependencies in detail and is aware of the need to fix - this situation. - - - - Thus far, this section has limited discussion to the direct - inputs into a task. - Information based on direct inputs is referred to as the - "basehash" in the code. - However, the question of a task's indirect inputs still - exits - items already built and present in the - Build Directory. - The checksum (or signature) for a particular task needs to add - the hashes of all the tasks on which the particular task - depends. - Choosing which dependencies to add is a policy decision. - However, the effect is to generate a master checksum that - combines the basehash and the hashes of the task's - dependencies. - - - - At the code level, a variety of ways exist by which both the - basehash and the dependent task hashes can be influenced. - Within the BitBake configuration file, you can give BitBake - some extra information to help it construct the basehash. - The following statement effectively results in a list of - global variable dependency excludes (i.e. variables never - included in any checksum): - - BB_HASHBASE_WHITELIST ?= "TMPDIR FILE PATH PWD BB_TASKHASH BBPATH DL_DIR \ - SSTATE_DIR THISDIR FILESEXTRAPATHS FILE_DIRNAME HOME LOGNAME SHELL TERM \ - USER FILESPATH STAGING_DIR_HOST STAGING_DIR_TARGET COREBASE PRSERV_HOST \ - PRSERV_DUMPDIR PRSERV_DUMPFILE PRSERV_LOCKDOWN PARALLEL_MAKE \ - CCACHE_DIR EXTERNAL_TOOLCHAIN CCACHE CCACHE_DISABLE LICENSE_PATH SDKPKGSUFFIX" - - The previous example excludes - WORKDIR - since that variable is actually constructed as a path within - TMPDIR, - which is on the whitelist. - - - - The rules for deciding which hashes of dependent tasks to - include through dependency chains are more complex and are - generally accomplished with a Python function. - The code in meta/lib/oe/sstatesig.py shows - two examples of this and also illustrates how you can insert - your own policy into the system if so desired. - This file defines the two basic signature generators - OE-Core - uses: "OEBasic" and "OEBasicHash". - By default, a dummy "noop" signature handler is enabled - in BitBake. - This means that behavior is unchanged from previous versions. - OE-Core uses the "OEBasicHash" signature handler by default - through this setting in the bitbake.conf - file: - - BB_SIGNATURE_HANDLER ?= "OEBasicHash" - - The "OEBasicHash" BB_SIGNATURE_HANDLER - is the same as the "OEBasic" version but adds the task hash to - the - stamp files. - This results in any metadata change that changes the task hash, - automatically causing the task to be run again. - This removes the need to bump - PR - values, and changes to metadata automatically ripple across - the build. - - - - It is also worth noting that the end result of these - signature generators is to make some dependency and hash - information available to the build. - This information includes: - - - BB_BASEHASH_task-taskname: - The base hashes for each task in the recipe. - - - BB_BASEHASH_filename:taskname: - The base hashes for each dependent task. - - - BBHASHDEPS_filename:taskname: - The task dependencies for each task. - - - BB_TASKHASH: - The hash of the currently running task. - - - -
- -
- Shared State - - - Checksums and dependencies, as discussed in the previous - section, solve half the problem of supporting a shared state. - The other half of the problem is being able to use checksum - information during the build and being able to reuse or rebuild - specific components. - - - - The - sstate - class is a relatively generic implementation of how to - "capture" a snapshot of a given task. - The idea is that the build process does not care about the - source of a task's output. - Output could be freshly built or it could be downloaded and - unpacked from somewhere. - In other words, the build process does not need to worry about - its origin. - - - - Two types of output exist. - One type is just about creating a directory in - WORKDIR. - A good example is the output of either - do_install - or - do_package. - The other type of output occurs when a set of data is merged - into a shared directory tree such as the sysroot. - - - - The Yocto Project team has tried to keep the details of the - implementation hidden in sstate class. - From a user's perspective, adding shared state wrapping to a - task is as simple as this - do_deploy - example taken from the - deploy - class: - - DEPLOYDIR = "${WORKDIR}/deploy-${PN}" - SSTATETASKS += "do_deploy" - do_deploy[sstate-inputdirs] = "${DEPLOYDIR}" - do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}" - - python do_deploy_setscene () { - sstate_setscene(d) - } - addtask do_deploy_setscene - do_deploy[dirs] = "${DEPLOYDIR} ${B}" - do_deploy[stamp-extra-info] = "${MACHINE_ARCH}" - - The following list explains the previous example: - - - Adding "do_deploy" to SSTATETASKS - adds some required sstate-related processing, which is - implemented in the - sstate - class, to before and after the - do_deploy - task. - - - The - do_deploy[sstate-inputdirs] = "${DEPLOYDIR}" - declares that do_deploy places its - output in ${DEPLOYDIR} when run - normally (i.e. when not using the sstate cache). - This output becomes the input to the shared state cache. - - - The - do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}" - line causes the contents of the shared state cache to be - copied to ${DEPLOY_DIR_IMAGE}. - - If do_deploy is not already in - the shared state cache or if its input checksum - (signature) has changed from when the output was - cached, the task runs to populate the shared - state cache, after which the contents of the shared - state cache is copied to - ${DEPLOY_DIR_IMAGE}. - If do_deploy is in the shared - state cache and its signature indicates that the - cached output is still valid (i.e. if no - relevant task inputs have changed), then the - contents of the shared state cache copies - directly to - ${DEPLOY_DIR_IMAGE} by the - do_deploy_setscene task - instead, skipping the - do_deploy task. - - - - The following task definition is glue logic needed to - make the previous settings effective: - - python do_deploy_setscene () { - sstate_setscene(d) - } - addtask do_deploy_setscene - - sstate_setscene() takes the flags - above as input and accelerates the - do_deploy task through the - shared state cache if possible. - If the task was accelerated, - sstate_setscene() returns True. - Otherwise, it returns False, and the normal - do_deploy task runs. - For more information, see the - "setscene" - section in the BitBake User Manual. - - - The do_deploy[dirs] = "${DEPLOYDIR} ${B}" - line creates ${DEPLOYDIR} and - ${B} before the - do_deploy task runs, and also sets - the current working directory of - do_deploy to - ${B}. - For more information, see the - "Variable Flags" - section in the BitBake User Manual. - - In cases where - sstate-inputdirs and - sstate-outputdirs would be the - same, you can use - sstate-plaindirs. - For example, to preserve the - ${PKGD} and - ${PKGDEST} output from the - do_package - task, use the following: - - do_package[sstate-plaindirs] = "${PKGD} ${PKGDEST}" - - - - - The do_deploy[stamp-extra-info] = "${MACHINE_ARCH}" - line appends extra metadata to the - stamp file. - In this case, the metadata makes the task specific - to a machine's architecture. - See - "The Task List" - section in the BitBake User Manual for more - information on the stamp-extra-info - flag. - - - sstate-inputdirs and - sstate-outputdirs can also be used - with multiple directories. - For example, the following declares - PKGDESTWORK and - SHLIBWORK as shared state - input directories, which populates the shared state - cache, and PKGDATA_DIR and - SHLIBSDIR as the corresponding - shared state output directories: - - do_package[sstate-inputdirs] = "${PKGDESTWORK} ${SHLIBSWORKDIR}" - do_package[sstate-outputdirs] = "${PKGDATA_DIR} ${SHLIBSDIR}" - - - - These methods also include the ability to take a - lockfile when manipulating shared state directory - structures, for cases where file additions or removals - are sensitive: - - do_package[sstate-lockfile] = "${PACKAGELOCK}" - - - - - - - Behind the scenes, the shared state code works by looking in - SSTATE_DIR - and - SSTATE_MIRRORS - for shared state files. - Here is an example: - - SSTATE_MIRRORS ?= "\ - file://.* http://someserver.tld/share/sstate/PATH;downloadfilename=PATH \n \ - file://.* file:///some/local/dir/sstate/PATH" - - - The shared state directory - (SSTATE_DIR) is organized into - two-character subdirectories, where the subdirectory - names are based on the first two characters of the hash. - If the shared state directory structure for a mirror has the - same structure as SSTATE_DIR, you must - specify "PATH" as part of the URI to enable the build system - to map to the appropriate subdirectory. - - - - - The shared state package validity can be detected just by - looking at the filename since the filename contains the task - checksum (or signature) as described earlier in this section. - If a valid shared state package is found, the build process - downloads it and uses it to accelerate the task. - - - - The build processes use the *_setscene - tasks for the task acceleration phase. - BitBake goes through this phase before the main execution - code and tries to accelerate any tasks for which it can find - shared state packages. - If a shared state package for a task is available, the - shared state package is used. - This means the task and any tasks on which it is dependent - are not executed. - - - - As a real world example, the aim is when building an IPK-based - image, only the - do_package_write_ipk - tasks would have their shared state packages fetched and - extracted. - Since the sysroot is not used, it would never get extracted. - This is another reason why a task-based approach is preferred - over a recipe-based approach, which would have to install the - output from every task. - -
-
- -
- Automatically Added Runtime Dependencies - - - The OpenEmbedded build system automatically adds common types of - runtime dependencies between packages, which means that you do not - need to explicitly declare the packages using - RDEPENDS. - Three automatic mechanisms exist (shlibdeps, - pcdeps, and depchains) - that handle shared libraries, package configuration (pkg-config) - modules, and -dev and - -dbg packages, respectively. - For other types of runtime dependencies, you must manually declare - the dependencies. - - - shlibdeps: - During the - do_package - task of each recipe, all shared libraries installed by the - recipe are located. - For each shared library, the package that contains the - shared library is registered as providing the shared - library. - More specifically, the package is registered as providing - the - soname - of the library. - The resulting shared-library-to-package mapping - is saved globally in - PKGDATA_DIR - by the - do_packagedata - task. - - Simultaneously, all executables and shared libraries - installed by the recipe are inspected to see what shared - libraries they link against. - For each shared library dependency that is found, - PKGDATA_DIR is queried to - see if some package (likely from a different recipe) - contains the shared library. - If such a package is found, a runtime dependency is added - from the package that depends on the shared library to the - package that contains the library. - - The automatically added runtime dependency also - includes a version restriction. - This version restriction specifies that at least the - current version of the package that provides the shared - library must be used, as if - "package (>= version)" - had been added to RDEPENDS. - This forces an upgrade of the package containing the shared - library when installing the package that depends on the - library, if needed. - - If you want to avoid a package being registered as - providing a particular shared library (e.g. because the library - is for internal use only), then add the library to - PRIVATE_LIBS - inside the package's recipe. - - - pcdeps: - During the do_package task of each - recipe, all pkg-config modules - (*.pc files) installed by the recipe - are located. - For each module, the package that contains the module is - registered as providing the module. - The resulting module-to-package mapping is saved globally in - PKGDATA_DIR by the - do_packagedata task. - - Simultaneously, all pkg-config modules installed by - the recipe are inspected to see what other pkg-config - modules they depend on. - A module is seen as depending on another module if it - contains a "Requires:" line that specifies the other module. - For each module dependency, - PKGDATA_DIR is queried to see if some - package contains the module. - If such a package is found, a runtime dependency is added - from the package that depends on the module to the package - that contains the module. - - The pcdeps mechanism most often - infers dependencies between -dev - packages. - - - - depchains: - If a package foo depends on a package - bar, then foo-dev - and foo-dbg are also made to depend on - bar-dev and - bar-dbg, respectively. - Taking the -dev packages as an - example, the bar-dev package might - provide headers and shared library symlinks needed by - foo-dev, which shows the need - for a dependency between the packages. - - The dependencies added by - depchains are in the form of - RRECOMMENDS. - - By default, foo-dev also has an - RDEPENDS-style dependency on - foo, because the default value of - RDEPENDS_${PN}-dev (set in - bitbake.conf) includes - "${PN}". - - - To ensure that the dependency chain is never broken, - -dev and -dbg - packages are always generated by default, even if the - packages turn out to be empty. - See the - ALLOW_EMPTY - variable for more information. - - - - - - The do_package task depends on the - do_packagedata task of each recipe in - DEPENDS - through use of a - [deptask] - declaration, which guarantees that the required - shared-library/module-to-package mapping information will be available - when needed as long as DEPENDS has been - correctly set. - -
- -
- Fakeroot and Pseudo - - - Some tasks are easier to implement when allowed to perform certain - operations that are normally reserved for the root user (e.g. - do_install, - do_package_write*, - do_rootfs, - and - do_image*). - For example, the do_install task benefits - from being able to set the UID and GID of installed files to - arbitrary values. - - - - One approach to allowing tasks to perform root-only operations - would be to require - BitBake - to run as root. - However, this method is cumbersome and has security issues. - The approach that is actually used is to run tasks that benefit - from root privileges in a "fake" root environment. - Within this environment, the task and its child processes believe - that they are running as the root user, and see an internally - consistent view of the filesystem. - As long as generating the final output (e.g. a package or an image) - does not require root privileges, the fact that some earlier - steps ran in a fake root environment does not cause problems. - - - - The capability to run tasks in a fake root environment is known as - "fakeroot", - which is derived from the BitBake keyword/variable - flag that requests a fake root environment for a task. - - - - In the - OpenEmbedded build system, - the program that implements fakeroot is known as - Pseudo. - Pseudo overrides system calls by using the environment variable - LD_PRELOAD, which results in the illusion - of running as root. - To keep track of "fake" file ownership and permissions resulting - from operations that require root permissions, Pseudo uses - an SQLite 3 database. - This database is stored in - ${WORKDIR}/pseudo/files.db - for individual recipes. - Storing the database in a file as opposed to in memory - gives persistence between tasks and builds, which is not - accomplished using fakeroot. - Caution - If you add your own task that manipulates the same files or - directories as a fakeroot task, then that task also needs to - run under fakeroot. - Otherwise, the task cannot run root-only operations, and - cannot see the fake file ownership and permissions set by the - other task. - You need to also add a dependency on - virtual/fakeroot-native:do_populate_sysroot, - giving the following: - - fakeroot do_mytask () { - ... - } - do_mytask[depends] += "virtual/fakeroot-native:do_populate_sysroot" - - - For more information, see the - FAKEROOT* - variables in the BitBake User Manual. - You can also reference the - "Why Not Fakeroot?" - article for background information on Fakeroot and Pseudo. - -
- - diff --git a/documentation/overview-manual/overview-manual-customization.xsl b/documentation/overview-manual/overview-manual-customization.xsl deleted file mode 100644 index 1dd91bde80..0000000000 --- a/documentation/overview-manual/overview-manual-customization.xsl +++ /dev/null @@ -1,29 +0,0 @@ - - - - - - - - - - - - - - - - - - - - - - - diff --git a/documentation/overview-manual/overview-manual-development-environment.xml b/documentation/overview-manual/overview-manual-development-environment.xml deleted file mode 100644 index 08ad071316..0000000000 --- a/documentation/overview-manual/overview-manual-development-environment.xml +++ /dev/null @@ -1,954 +0,0 @@ - %poky; ] > - - - -The Yocto Project Development Environment - - - This chapter takes a look at the Yocto Project development - environment. - The chapter provides Yocto Project Development environment concepts that - help you understand how work is accomplished in an open source environment, - which is very different as compared to work accomplished in a closed, - proprietary environment. - - - - Specifically, this chapter addresses open source philosophy, source - repositories, workflows, Git, and licensing. - - -
- Open Source Philosophy - - - Open source philosophy is characterized by software development - directed by peer production and collaboration through an active - community of developers. - Contrast this to the more standard centralized development models - used by commercial software companies where a finite set of developers - produces a product for sale using a defined set of procedures that - ultimately result in an end product whose architecture and source - material are closed to the public. - - - - Open source projects conceptually have differing concurrent agendas, - approaches, and production. - These facets of the development process can come from anyone in the - public (community) who has a stake in the software project. - The open source environment contains new copyright, licensing, domain, - and consumer issues that differ from the more traditional development - environment. - In an open source environment, the end product, source material, - and documentation are all available to the public at no cost. - - - - A benchmark example of an open source project is the Linux kernel, - which was initially conceived and created by Finnish computer science - student Linus Torvalds in 1991. - Conversely, a good example of a non-open source project is the - Windows family of operating - systems developed by - Microsoft Corporation. - - - - Wikipedia has a good historical description of the Open Source - Philosophy - here. - You can also find helpful information on how to participate in the - Linux Community - here. - -
- -
- The Development Host - - - A development host or - build host - is key to using the Yocto Project. - Because the goal of the Yocto Project is to develop images or - applications that run on embedded hardware, development of those - images and applications generally takes place on a system not - intended to run the software - the development host. - - - - You need to set up a development host in order to use it with the - Yocto Project. - Most find that it is best to have a native Linux machine function as - the development host. - However, it is possible to use a system that does not run Linux - as its operating system as your development host. - When you have a Mac or Windows-based system, you can set it up - as the development host by using - CROPS, - which leverages - Docker Containers. - Once you take the steps to set up a CROPS machine, you effectively - have access to a shell environment that is similar to what you see - when using a Linux-based development host. - For the steps needed to set up a system using CROPS, see the - "Setting Up to Use CROss PlatformS (CROPS)" - section in the Yocto Project Development Tasks Manual. - - - - If your development host is going to be a system that runs a Linux - distribution, steps still exist that you must take to prepare the - system for use with the Yocto Project. - You need to be sure that the Linux distribution on the system is - one that supports the Yocto Project. - You also need to be sure that the correct set of host packages are - installed that allow development using the Yocto Project. - For the steps needed to set up a development host that runs Linux, - see the - "Setting Up a Native Linux Host" - section in the Yocto Project Development Tasks Manual. - - - - Once your development host is set up to use the Yocto Project, - several methods exist for you to do work in the Yocto Project - environment: - - - Command Lines, BitBake, and Shells: - Traditional development in the Yocto Project involves using the - OpenEmbedded build system, - which uses BitBake, in a command-line environment from a shell - on your development host. - You can accomplish this from a host that is a native Linux - machine or from a host that has been set up with CROPS. - Either way, you create, modify, and build images and - applications all within a shell-based environment using - components and tools available through your Linux distribution - and the Yocto Project. - - For a general flow of the build procedures, see the - "Building a Simple Image" - section in the Yocto Project Development Tasks Manual. - - - Board Support Package (BSP) Development: - Development of BSPs involves using the Yocto Project to - create and test layers that allow easy development of - images and applications targeted for specific hardware. - To development BSPs, you need to take some additional steps - beyond what was described in setting up a development host. - - - The - Yocto Project Board Support Package (BSP) Developer's Guide - provides BSP-related development information. - For specifics on development host preparation, see the - "Preparing Your Build Host to Work With BSP Layers" - section in the Yocto Project Board Support Package (BSP) - Developer's Guide. - - - Kernel Development: - If you are going to be developing kernels using the Yocto - Project you likely will be using devtool. - A workflow using devtool makes kernel - development quicker by reducing iteration cycle times. - - The - Yocto Project Linux Kernel Development Manual - provides kernel-related development information. - For specifics on development host preparation, see the - "Preparing the Build Host to Work on the Kernel" - section in the Yocto Project Linux Kernel Development Manual. - - - Using Toaster: - The other Yocto Project development method that involves an - interface that effectively puts the Yocto Project into the - background is Toaster. - Toaster provides an interface to the OpenEmbedded build system. - The interface enables you to configure and run your builds. - Information about builds is collected and stored in a database. - You can use Toaster to configure and start builds on multiple - remote build servers. - - For steps that show you how to set up your development - host to use Toaster and on how to use Toaster in general, - see the - Toaster User Manual. - - - -
- -
- Yocto Project Source Repositories - - - The Yocto Project team maintains complete source repositories for all - Yocto Project files at - . - This web-based source code browser is organized into categories by - function such as IDE Plugins, Matchbox, Poky, Yocto Linux Kernel, and - so forth. - From the interface, you can click on any particular item in the "Name" - column and see the URL at the bottom of the page that you need to clone - a Git repository for that particular item. - Having a local Git repository of the - Source Directory, - which is usually named "poky", allows - you to make changes, contribute to the history, and ultimately enhance - the Yocto Project's tools, Board Support Packages, and so forth. - - - - For any supported release of Yocto Project, you can also go to the - Yocto Project Website and - select the "DOWNLOADS" item from the "SOFTWARE" menu and get a - released tarball of the poky repository, any - supported BSP tarball, or Yocto Project tools. - Unpacking these tarballs gives you a snapshot of the released - files. - Notes - - - The recommended method for setting up the Yocto Project - Source Directory - and the files for supported BSPs - (e.g., meta-intel) is to use - Git to create a local copy of - the upstream repositories. - - - Be sure to always work in matching branches for both - the selected BSP repository and the Source Directory - (i.e. poky) repository. - For example, if you have checked out the "master" branch - of poky and you are going to use - meta-intel, be sure to checkout the - "master" branch of meta-intel. - - - - - - - In summary, here is where you can get the project files needed for - development: - - - - Source Repositories: - - This area contains IDE Plugins, Matchbox, Poky, Poky Support, - Tools, Yocto Linux Kernel, and Yocto Metadata Layers. - You can create local copies of Git repositories for each of - these areas. - - - - For steps on how to view and access these upstream Git - repositories, see the - "Accessing Source Repositories" - Section in the Yocto Project Development Tasks Manual. - - - - Index of /releases: - - This is an index of releases such as Poky, Pseudo, installers - for cross-development toolchains, miscellaneous support - and all released versions of Yocto Project in the form of - images or tarballs. - Downloading and extracting these files does not produce a local - copy of the Git repository but rather a snapshot of a - particular release or image. - - - - For steps on how to view and access these files, see the - "Accessing Index of Releases" - section in the Yocto Project Development Tasks Manual. - - - "DOWNLOADS" page for the - Yocto Project Website: - - - The Yocto Project website includes a "DOWNLOADS" page - accessible through the "SOFTWARE" menu that allows you to - download any Yocto Project release, tool, and Board Support - Package (BSP) in tarball form. - The tarballs are similar to those found in the - Index of /releases: - area. - - - - For steps on how to use the "DOWNLOADS" page, see the - "Using the Downloads Page" - section in the Yocto Project Development Tasks Manual. - - - -
- -
- Git Workflows and the Yocto Project - - - Developing using the Yocto Project likely requires the use of - Git. - Git is a free, open source distributed version control system - used as part of many collaborative design environments. - This section provides workflow concepts using the Yocto Project and - Git. - In particular, the information covers basic practices that describe - roles and actions in a collaborative development environment. - - If you are familiar with this type of development environment, you - might not want to read this section. - - - - - The Yocto Project files are maintained using Git in "branches" - whose Git histories track every change and whose structures - provide branches for all diverging functionality. - Although there is no need to use Git, many open source projects do so. - - - - For the Yocto Project, a key individual called the "maintainer" is - responsible for the integrity of the "master" branch of a given Git - repository. - The "master" branch is the "upstream" repository from which final or - most recent builds of a project occur. - The maintainer is responsible for accepting changes from other - developers and for organizing the underlying branch structure to - reflect release strategies and so forth. - - For information on finding out who is responsible for (maintains) - a particular area of code in the Yocto Project, see the - "Submitting a Change to the Yocto Project" - section of the Yocto Project Development Tasks Manual. - - - - - The Yocto Project poky Git repository also has an - upstream contribution Git repository named - poky-contrib. - You can see all the branches in this repository using the web interface - of the - Source Repositories organized - within the "Poky Support" area. - These branches hold changes (commits) to the project that have been - submitted or committed by the Yocto Project development team and by - community members who contribute to the project. - The maintainer determines if the changes are qualified to be moved - from the "contrib" branches into the "master" branch of the Git - repository. - - - - Developers (including contributing community members) create and - maintain cloned repositories of upstream branches. - The cloned repositories are local to their development platforms and - are used to develop changes. - When a developer is satisfied with a particular feature or change, - they "push" the change to the appropriate "contrib" repository. - - - - Developers are responsible for keeping their local repository - up-to-date with whatever upstream branch they are working against. - They are also responsible for straightening out any conflicts that - might arise within files that are being worked on simultaneously by - more than one person. - All this work is done locally on the development host before - anything is pushed to a "contrib" area and examined at the maintainer's - level. - - - - A somewhat formal method exists by which developers commit changes - and push them into the "contrib" area and subsequently request that - the maintainer include them into an upstream branch. - This process is called "submitting a patch" or "submitting a change." - For information on submitting patches and changes, see the - "Submitting a Change to the Yocto Project" - section in the Yocto Project Development Tasks Manual. - - - - In summary, a single point of entry - exists for changes into a "master" or development branch of the - Git repository, which is controlled by the project's maintainer. - And, a set of developers exist who independently develop, test, and - submit changes to "contrib" areas for the maintainer to examine. - The maintainer then chooses which changes are going to become a - permanent part of the project. - - - - - - - - While each development environment is unique, there are some best - practices or methods that help development run smoothly. - The following list describes some of these practices. - For more information about Git workflows, see the workflow topics in - the - Git Community Book. - - - Make Small Changes: - It is best to keep the changes you commit small as compared to - bundling many disparate changes into a single commit. - This practice not only keeps things manageable but also allows - the maintainer to more easily include or refuse changes. - - - Make Complete Changes: - It is also good practice to leave the repository in a - state that allows you to still successfully build your project. - In other words, do not commit half of a feature, - then add the other half as a separate, later commit. - Each commit should take you from one buildable project state - to another buildable state. - - - Use Branches Liberally: - It is very easy to create, use, and delete local branches in - your working Git repository on the development host. - You can name these branches anything you like. - It is helpful to give them names associated with the particular - feature or change on which you are working. - Once you are done with a feature or change and have merged it - into your local master branch, simply discard the temporary - branch. - - - Merge Changes: - The git merge command allows you to take - the changes from one branch and fold them into another branch. - This process is especially helpful when more than a single - developer might be working on different parts of the same - feature. - Merging changes also automatically identifies any collisions - or "conflicts" that might happen as a result of the same lines - of code being altered by two different developers. - - - Manage Branches: - Because branches are easy to use, you should use a system - where branches indicate varying levels of code readiness. - For example, you can have a "work" branch to develop in, a - "test" branch where the code or change is tested, a "stage" - branch where changes are ready to be committed, and so forth. - As your project develops, you can merge code across the - branches to reflect ever-increasing stable states of the - development. - - - Use Push and Pull: - The push-pull workflow is based on the concept of developers - "pushing" local commits to a remote repository, which is - usually a contribution repository. - This workflow is also based on developers "pulling" known - states of the project down into their local development - repositories. - The workflow easily allows you to pull changes submitted by - other developers from the upstream repository into your - work area ensuring that you have the most recent software - on which to develop. - The Yocto Project has two scripts named - create-pull-request and - send-pull-request that ship with the - release to facilitate this workflow. - You can find these scripts in the scripts - folder of the - Source Directory. - For information on how to use these scripts, see the - "Using Scripts to Push a Change Upstream and Request a Pull" - section in the Yocto Project Development Tasks Manual. - - - Patch Workflow: - This workflow allows you to notify the maintainer through an - email that you have a change (or patch) you would like - considered for the "master" branch of the Git repository. - To send this type of change, you format the patch and then - send the email using the Git commands - git format-patch and - git send-email. - For information on how to use these scripts, see the - "Submitting a Change to the Yocto Project" - section in the Yocto Project Development Tasks Manual. - - - -
- -
- Git - - - The Yocto Project makes extensive use of Git, which is a - free, open source distributed version control system. - Git supports distributed development, non-linear development, - and can handle large projects. - It is best that you have some fundamental understanding - of how Git tracks projects and how to work with Git if - you are going to use the Yocto Project for development. - This section provides a quick overview of how Git works and - provides you with a summary of some essential Git commands. - Notes - - - For more information on Git, see - . - - - If you need to download Git, it is recommended that you add - Git to your system through your distribution's "software - store" (e.g. for Ubuntu, use the Ubuntu Software feature). - For the Git download page, see - . - - - For information beyond the introductory nature in this - section, see the - "Locating Yocto Project Source Files" - section in the Yocto Project Development Tasks Manual. - - - - - -
- Repositories, Tags, and Branches - - - As mentioned briefly in the previous section and also in the - "Git Workflows and the Yocto Project" - section, the Yocto Project maintains source repositories at - . - If you look at this web-interface of the repositories, each item - is a separate Git repository. - - - - Git repositories use branching techniques that track content - change (not files) within a project (e.g. a new feature or updated - documentation). - Creating a tree-like structure based on project divergence allows - for excellent historical information over the life of a project. - This methodology also allows for an environment from which you can - do lots of local experimentation on projects as you develop - changes or new features. - - - - A Git repository represents all development efforts for a given - project. - For example, the Git repository poky contains - all changes and developments for that repository over the course - of its entire life. - That means that all changes that make up all releases are captured. - The repository maintains a complete history of changes. - - - - You can create a local copy of any repository by "cloning" it - with the git clone command. - When you clone a Git repository, you end up with an identical - copy of the repository on your development system. - Once you have a local copy of a repository, you can take steps to - develop locally. - For examples on how to clone Git repositories, see the - "Locating Yocto Project Source Files" - section in the Yocto Project Development Tasks Manual. - - - - It is important to understand that Git tracks content change and - not files. - Git uses "branches" to organize different development efforts. - For example, the poky repository has - several branches that include the current "&DISTRO_NAME_NO_CAP;" - branch, the "master" branch, and many branches for past - Yocto Project releases. - You can see all the branches by going to - and - clicking on the - [...] - link beneath the "Branch" heading. - - - - Each of these branches represents a specific area of development. - The "master" branch represents the current or most recent - development. - All other branches represent offshoots of the "master" branch. - - - - When you create a local copy of a Git repository, the copy has - the same set of branches as the original. - This means you can use Git to create a local working area - (also called a branch) that tracks a specific development branch - from the upstream source Git repository. - in other words, you can define your local Git environment to - work on any development branch in the repository. - To help illustrate, consider the following example Git commands: - - $ cd ~ - $ git clone git://git.yoctoproject.org/poky - $ cd poky - $ git checkout -b &DISTRO_NAME_NO_CAP; origin/&DISTRO_NAME_NO_CAP; - - In the previous example after moving to the home directory, the - git clone command creates a - local copy of the upstream poky Git repository. - By default, Git checks out the "master" branch for your work. - After changing the working directory to the new local repository - (i.e. poky), the - git checkout command creates - and checks out a local branch named "&DISTRO_NAME_NO_CAP;", which - tracks the upstream "origin/&DISTRO_NAME_NO_CAP;" branch. - Changes you make while in this branch would ultimately affect - the upstream "&DISTRO_NAME_NO_CAP;" branch of the - poky repository. - - - - It is important to understand that when you create and checkout a - local working branch based on a branch name, - your local environment matches the "tip" of that particular - development branch at the time you created your local branch, - which could be different from the files in the "master" branch - of the upstream repository. - In other words, creating and checking out a local branch based on - the "&DISTRO_NAME_NO_CAP;" branch name is not the same as - checking out the "master" branch in the repository. - Keep reading to see how you create a local snapshot of a Yocto - Project Release. - - - - Git uses "tags" to mark specific changes in a repository branch - structure. - Typically, a tag is used to mark a special point such as the final - change (or commit) before a project is released. - You can see the tags used with the poky Git - repository by going to - and - clicking on the - [...] - link beneath the "Tag" heading. - - - - Some key tags for the poky repository are - jethro-14.0.3, - morty-16.0.1, - pyro-17.0.0, and - &DISTRO_NAME_NO_CAP;-&POKYVERSION;. - These tags represent Yocto Project releases. - - - - When you create a local copy of the Git repository, you also - have access to all the tags in the upstream repository. - Similar to branches, you can create and checkout a local working - Git branch based on a tag name. - When you do this, you get a snapshot of the Git repository that - reflects the state of the files when the change was made associated - with that tag. - The most common use is to checkout a working branch that matches - a specific Yocto Project release. - Here is an example: - - $ cd ~ - $ git clone git://git.yoctoproject.org/poky - $ cd poky - $ git fetch --tags - $ git checkout tags/rocko-18.0.0 -b my_rocko-18.0.0 - - In this example, the name of the top-level directory of your - local Yocto Project repository is poky. - After moving to the poky directory, the - git fetch command makes all the upstream - tags available locally in your repository. - Finally, the git checkout command - creates and checks out a branch named "my-rocko-18.0.0" that is - based on the upstream branch whose "HEAD" matches the - commit in the repository associated with the "rocko-18.0.0" tag. - The files in your repository now exactly match that particular - Yocto Project release as it is tagged in the upstream Git - repository. - It is important to understand that when you create and - checkout a local working branch based on a tag, your environment - matches a specific point in time and not the entire development - branch (i.e. from the "tip" of the branch backwards). - -
- -
- Basic Commands - - - Git has an extensive set of commands that lets you manage changes - and perform collaboration over the life of a project. - Conveniently though, you can manage with a small set of basic - operations and workflows once you understand the basic - philosophy behind Git. - You do not have to be an expert in Git to be functional. - A good place to look for instruction on a minimal set of Git - commands is - here. - - - - The following list of Git commands briefly describes some basic - Git operations as a way to get started. - As with any set of commands, this list (in most cases) simply shows - the base command and omits the many arguments it supports. - See the Git documentation for complete descriptions and strategies - on how to use these commands: - - - git init: - Initializes an empty Git repository. - You cannot use Git commands unless you have a - .git repository. - - - git clone: - Creates a local clone of a Git repository that is on - equal footing with a fellow developer's Git repository - or an upstream repository. - - - git add: - Locally stages updated file contents to the index that - Git uses to track changes. - You must stage all files that have changed before you - can commit them. - - - git commit: - Creates a local "commit" that documents the changes you - made. - Only changes that have been staged can be committed. - Commits are used for historical purposes, for determining - if a maintainer of a project will allow the change, - and for ultimately pushing the change from your local - Git repository into the project's upstream repository. - - - git status: - Reports any modified files that possibly need to be - staged and gives you a status of where you stand regarding - local commits as compared to the upstream repository. - - - git checkout branch-name: - Changes your local working branch and in this form - assumes the local branch already exists. - This command is analogous to "cd". - - - git checkout –b working-branch upstream-branch: - Creates and checks out a working branch on your local - machine. - The local branch tracks the upstream branch. - You can use your local branch to isolate your work. - It is a good idea to use local branches when adding - specific features or changes. - Using isolated branches facilitates easy removal of - changes if they do not work out. - - git branch: - Displays the existing local branches associated with your - local repository. - The branch that you have currently checked out is noted - with an asterisk character. - - - git branch -D branch-name: - Deletes an existing local branch. - You need to be in a local branch other than the one you - are deleting in order to delete - branch-name. - - - git pull --rebase: - Retrieves information from an upstream Git repository - and places it in your local Git repository. - You use this command to make sure you are synchronized with - the repository from which you are basing changes - (.e.g. the "master" branch). - The "--rebase" option ensures that any local commits you - have in your branch are preserved at the top of your - local branch. - - - git push repo-name local-branch:upstream-branch: - Sends all your committed local changes to the upstream Git - repository that your local repository is tracking - (e.g. a contribution repository). - The maintainer of the project draws from these repositories - to merge changes (commits) into the appropriate branch - of project's upstream repository. - - - git merge: - Combines or adds changes from one - local branch of your repository with another branch. - When you create a local Git repository, the default branch - is named "master". - A typical workflow is to create a temporary branch that is - based off "master" that you would use for isolated work. - You would make your changes in that isolated branch, - stage and commit them locally, switch to the "master" - branch, and then use the git merge - command to apply the changes from your isolated branch - into the currently checked out branch (e.g. "master"). - After the merge is complete and if you are done with - working in that isolated branch, you can safely delete - the isolated branch. - - - git cherry-pick commits: - Choose and apply specific commits from one branch - into another branch. - There are times when you might not be able to merge - all the changes in one branch with - another but need to pick out certain ones. - - - gitk: - Provides a GUI view of the branches and changes in your - local Git repository. - This command is a good way to graphically see where things - have diverged in your local repository. - - You need to install the gitk - package on your development system to use this - command. - - - - git log: - Reports a history of your commits to the repository. - This report lists all commits regardless of whether you - have pushed them upstream or not. - - - git diff: - Displays line-by-line differences between a local - working file and the same file as understood by Git. - This command is useful to see what you have changed - in any given file. - - - -
-
- -
- Licensing - - - Because open source projects are open to the public, they have - different licensing structures in place. - License evolution for both Open Source and Free Software has an - interesting history. - If you are interested in this history, you can find basic information - here: - - - Open source license history - - - Free software license history - - - - - - In general, the Yocto Project is broadly licensed under the - Massachusetts Institute of Technology (MIT) License. - MIT licensing permits the reuse of software within proprietary - software as long as the license is distributed with that software. - MIT is also compatible with the GNU General Public License (GPL). - Patches to the Yocto Project follow the upstream licensing scheme. - You can find information on the MIT license - here. - You can find information on the GNU GPL - here. - - - - When you build an image using the Yocto Project, the build process - uses a known list of licenses to ensure compliance. - You can find this list in the - Source Directory - at meta/files/common-licenses. - Once the build completes, the list of all licenses found and used - during that build are kept in the - Build Directory - at tmp/deploy/licenses. - - - - If a module requires a license that is not in the base list, the - build process generates a warning during the build. - These tools make it easier for a developer to be certain of the - licenses with which their shipped products must comply. - However, even with these tools it is still up to the developer to - resolve potential licensing issues. - - - - The base list of licenses used by the build process is a combination - of the Software Package Data Exchange (SPDX) list and the Open - Source Initiative (OSI) projects. - SPDX Group is a working group of - the Linux Foundation that maintains a specification for a standard - format for communicating the components, licenses, and copyrights - associated with a software package. - OSI is a corporation - dedicated to the Open Source Definition and the effort for reviewing - and approving licenses that conform to the Open Source Definition - (OSD). - - - - You can find a list of the combined SPDX and OSI licenses that the - Yocto Project uses in the - meta/files/common-licenses directory in your - Source Directory. - - - - For information that can help you maintain compliance with various - open source licensing during the lifecycle of a product created using - the Yocto Project, see the - "Maintaining Open Source License Compliance During Your Product's Lifecycle" - section in the Yocto Project Development Tasks Manual. - -
- - diff --git a/documentation/overview-manual/overview-manual-intro.xml b/documentation/overview-manual/overview-manual-intro.xml deleted file mode 100644 index 0e0bfed6e5..0000000000 --- a/documentation/overview-manual/overview-manual-intro.xml +++ /dev/null @@ -1,113 +0,0 @@ - %poky; ] > - - - - -The Yocto Project Overview and Concepts Manual -
- Welcome - - - Welcome to the Yocto Project Overview and Concepts Manual! - This manual introduces the Yocto Project by providing concepts, - software overviews, best-known-methods (BKMs), and any other - high-level introductory information suitable for a new Yocto - Project user. - - - - The following list describes what you can get from this manual: - - - Introducing the Yocto Project: - This chapter provides an introduction to the Yocto - Project. - You will learn about features and challenges of the - Yocto Project, the layer model, components and tools, - development methods, the - Poky - reference distribution, the OpenEmbedded build system - workflow, and some basic Yocto terms. - - - The Yocto Project Development Environment: - This chapter helps you get started understanding the - Yocto Project development environment. - You will learn about open source, development hosts, - Yocto Project source repositories, workflows using Git - and the Yocto Project, a Git primer, and information - about licensing. - - - Yocto Project Concepts: - This chapter presents various concepts regarding the - Yocto Project. - You can find conceptual information about components, - development, cross-toolchains, and so forth. - - - - - - This manual does not give you the following: - - - Step-by-step Instructions for Development Tasks: - Instructional procedures reside in other manuals within - the Yocto Project documentation set. - For example, the - Yocto Project Development Tasks Manual - provides examples on how to perform various development - tasks. - As another example, the - Yocto Project Application Development and the Extensible Software Development Kit (eSDK) - manual contains detailed instructions on how to install an - SDK, which is used to develop applications for target - hardware. - - - Reference Material: - This type of material resides in an appropriate reference - manual. - For example, system variables are documented in the - Yocto Project Reference Manual. - As another example, the - Yocto Project Board Support Package (BSP) Developer's Guide - contains reference information on BSPs. - - - Detailed Public Information Not Specific to the - Yocto Project: - For example, exhaustive information on how to use the - Source Control Manager Git is better covered with Internet - searches and official Git Documentation than through the - Yocto Project documentation. - - - -
- -
- Other Information - - - Because this manual presents information for many different - topics, supplemental information is recommended for full - comprehension. - For additional introductory information on the Yocto Project, see - the Yocto Project Website. - If you want to build an image with no knowledge of Yocto Project - as a way of quickly testing it out, see the - Yocto Project Quick Build - document. - For a comprehensive list of links and other documentation, see the - "Links and Related Documentation" - section in the Yocto Project Reference Manual. - -
- - diff --git a/documentation/overview-manual/overview-manual-style.css b/documentation/overview-manual/overview-manual-style.css deleted file mode 100644 index eec934161a..0000000000 --- a/documentation/overview-manual/overview-manual-style.css +++ /dev/null @@ -1,990 +0,0 @@ -/* - SPDX-License-Identifier: CC-BY-2.0-UK - - Generic XHTML / DocBook XHTML CSS Stylesheet. - - Browser wrangling and typographic design by - Oyvind Kolas / pippin@gimp.org - - Customised for Poky by - Matthew Allum / mallum@o-hand.com - - Thanks to: - Liam R. E. 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- What is the Yocto Project? - - - The Yocto Project is an open source collaboration project - that helps developers create custom Linux-based systems that are - designed for embedded products regardless of the product's hardware - architecture. - Yocto Project provides a flexible toolset and a development - environment that allows embedded device developers across the - world to collaborate through shared technologies, software stacks, - configurations, and best practices used to create these tailored - Linux images. - - - - Thousands of developers worldwide have discovered that Yocto - Project provides advantages in both systems and applications - development, archival and management benefits, and customizations - used for speed, footprint, and memory utilization. - The project is a standard when it comes to delivering embedded - software stacks. - The project allows software customizations and build interchange - for multiple hardware platforms as well as software stacks that - can be maintained and scaled. - - - - - - - - For further introductory information on the Yocto Project, you - might be interested in this - article - by Drew Moseley and in this short introductory - video. - - - - The remainder of this section overviews advantages and challenges - tied to the Yocto Project. - - -
- Features - - - The following list describes features and advantages of the - Yocto Project: - - - Widely Adopted Across the Industry: - Semiconductor, operating system, software, and - service vendors exist whose products and services - adopt and support the Yocto Project. - For a look at the Yocto Project community and - the companies involved with the Yocto - Project, see the "COMMUNITY" and "ECOSYSTEM" tabs - on the - Yocto Project - home page. - - - Architecture Agnostic: - Yocto Project supports Intel, ARM, MIPS, AMD, PPC - and other architectures. - Most ODMs, OSVs, and chip vendors create and supply - BSPs that support their hardware. - If you have custom silicon, you can create a BSP - that supports that architecture. - - Aside from lots of architecture support, the - Yocto Project fully supports a wide range of device - emulation through the Quick EMUlator (QEMU). - - - Images and Code Transfer Easily: - Yocto Project output can easily move between - architectures without moving to new development - environments. - Additionally, if you have used the Yocto Project to - create an image or application and you find yourself - not able to support it, commercial Linux vendors such - as Wind River, Mentor Graphics, Timesys, and ENEA could - take it and provide ongoing support. - These vendors have offerings that are built using - the Yocto Project. - - - Flexibility: - Corporations use the Yocto Project many different ways. - One example is to create an internal Linux distribution - as a code base the corporation can use across multiple - product groups. - Through customization and layering, a project group - can leverage the base Linux distribution to create - a distribution that works for their product needs. - - - Ideal for Constrained Embedded and IoT devices: - Unlike a full Linux distribution, you can use the - Yocto Project to create exactly what you need for - embedded devices. - You only add the feature support or packages that you - absolutely need for the device. - For devices that have display hardware, you can use - available system components such as X11, GTK+, Qt, - Clutter, and SDL (among others) to create a rich user - experience. - For devices that do not have a display or where you - want to use alternative UI frameworks, you can choose - to not install these components. - - - Comprehensive Toolchain Capabilities: - Toolchains for supported architectures satisfy most - use cases. - However, if your hardware supports features that are - not part of a standard toolchain, you can easily - customize that toolchain through specification of - platform-specific tuning parameters. - And, should you need to use a third-party toolchain, - mechanisms built into the Yocto Project allow for that. - - - Mechanism Rules Over Policy: - Focusing on mechanism rather than policy ensures that - you are free to set policies based on the needs of your - design instead of adopting decisions enforced by some - system software provider. - - - Uses a Layer Model: - The Yocto Project - layer infrastructure - groups related functionality into separate bundles. - You can incrementally add these grouped functionalities - to your project as needed. - Using layers to isolate and group functionality - reduces project complexity and redundancy, allows you - to easily extend the system, make customizations, - and keep functionality organized. - - - Supports Partial Builds: - You can build and rebuild individual packages as - needed. - Yocto Project accomplishes this through its - shared-state cache - (sstate) scheme. - Being able to build and debug components individually - eases project development. - - - Releases According to a Strict Schedule: - Major releases occur on a - six-month cycle - predictably in October and April. - The most recent two releases support point releases - to address common vulnerabilities and exposures. - This predictability is crucial for projects based on - the Yocto Project and allows development teams to - plan activities. - - - Rich Ecosystem of Individuals and Organizations: - For open source projects, the value of community is - very important. - Support forums, expertise, and active developers who - continue to push the Yocto Project forward are readily - available. - - - Binary Reproducibility: - The Yocto Project allows you to be very specific about - dependencies and achieves very high percentages of - binary reproducibility (e.g. 99.8% for - core-image-minimal). - When distributions are not specific about which - packages are pulled in and in what order to support - dependencies, other build systems can arbitrarily - include packages. - - - License Manifest: - The Yocto Project provides a - license manifest - for review by people who need to track the use of open - source licenses (e.g.legal teams). - - - -
- -
- Challenges - - - The following list presents challenges you might encounter - when developing using the Yocto Project: - - - Steep Learning Curve: - The Yocto Project has a steep learning curve and has - many different ways to accomplish similar tasks. - It can be difficult to choose how to proceed when - varying methods exist by which to accomplish a given - task. - - - Understanding What Changes You Need to Make - For Your Design Requires Some Research: - Beyond the simple tutorial stage, understanding what - changes need to be made for your particular design - can require a significant amount of research and - investigation. - For information that helps you transition from - trying out the Yocto Project to using it for your - project, see the - "What I wish I'd Known" - and - "Transitioning to a Custom Environment for Systems Development" - documents on the Yocto Project website. - - - Project Workflow Could Be Confusing: - The - Yocto Project workflow - could be confusing if you are used to traditional - desktop and server software development. - In a desktop development environment, mechanisms exist - to easily pull and install new packages, which are - typically pre-compiled binaries from servers accessible - over the Internet. - Using the Yocto Project, you must modify your - configuration and rebuild to add additional packages. - - - Working in a Cross-Build Environment Can - Feel Unfamiliar: - When developing code to run on a target, compilation, - execution, and testing done on the actual target - can be faster than running a BitBake build on a - development host and then deploying binaries to the - target for test. - While the Yocto Project does support development tools - on the target, the additional step of integrating your - changes back into the Yocto Project build environment - would be required. - Yocto Project supports an intermediate approach that - involves making changes on the development system - within the BitBake environment and then deploying only - the updated packages to the target. - - The Yocto Project - OpenEmbedded build system - produces packages in standard formats (i.e. RPM, - DEB, IPK, and TAR). - You can deploy these packages into the running system - on the target by using utilities on the target such - as rpm or - ipk. - - - Initial Build Times Can be Significant: - Long initial build times are unfortunately unavoidable - due to the large number of packages initially built - from scratch for a fully functioning Linux system. - Once that initial build is completed, however, the - shared-state (sstate) cache mechanism Yocto Project - uses keeps the system from rebuilding packages that - have not been "touched" since the last build. - The sstate mechanism significantly reduces times - for successive builds. - - - -
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- -
- The Yocto Project Layer Model - - - The Yocto Project's "Layer Model" is a development model for - embedded and IoT Linux creation that distinguishes the - Yocto Project from other simple build systems. - The Layer Model simultaneously supports collaboration and - customization. - Layers are repositories that contain related sets of instructions - that tell the - OpenEmbedded build system - what to do. - You can collaborate, share, and reuse layers. - - - - Layers can contain changes to previous instructions or settings - at any time. - This powerful override capability is what allows you to customize - previously supplied collaborative or community layers to suit your - product requirements. - - - - You use different layers to logically separate information in your - build. - As an example, you could have BSP, GUI, distro configuration, - middleware, or application layers. - Putting your entire build into one layer limits and complicates - future customization and reuse. - Isolating information into layers, on the other hand, helps - simplify future customizations and reuse. - You might find it tempting to keep everything in one layer when - working on a single project. - However, the more modular your Metadata, the easier - it is to cope with future changes. - Notes - - - Use Board Support Package (BSP) layers from silicon - vendors when possible. - - - Familiarize yourself with the - Yocto Project curated layer index - or the - OpenEmbedded layer index. - The latter contains more layers but they are less - universally validated. - - - Layers support the inclusion of technologies, hardware - components, and software components. - The - Yocto Project Compatible - designation provides a minimum level of standardization - that contributes to a strong ecosystem. - "YP Compatible" is applied to appropriate products and - software components such as BSPs, other OE-compatible - layers, and related open-source projects, allowing the - producer to use Yocto Project badges and branding - assets. - - - - - - - To illustrate how layers are used to keep things modular, consider - machine customizations. - These types of customizations typically reside in a special layer, - rather than a general layer, called a BSP Layer. - Furthermore, the machine customizations should be isolated from - recipes and Metadata that support a new GUI environment, - for example. - This situation gives you a couple of layers: one for the machine - configurations, and one for the GUI environment. - It is important to understand, however, that the BSP layer can - still make machine-specific additions to recipes within the GUI - environment layer without polluting the GUI layer itself - with those machine-specific changes. - You can accomplish this through a recipe that is a BitBake append - (.bbappend) file, which is described later - in this section. - - For general information on BSP layer structure, see the - Yocto Project Board Support Packages (BSP) Developer's Guide. - - - - - The - Source Directory - contains both general layers and BSP layers right out of the box. - You can easily identify layers that ship with a Yocto Project - release in the Source Directory by their names. - Layers typically have names that begin with the string - meta-. - - It is not a requirement that a layer name begin with the - prefix meta-, but it is a commonly - accepted standard in the Yocto Project community. - - For example, if you were to examine the - tree view - of the poky repository, you will see several - layers: meta, - meta-skeleton, - meta-selftest, - meta-poky, and - meta-yocto-bsp. - Each of these repositories represents a distinct layer. - - - - For procedures on how to create layers, see the - "Understanding and Creating Layers" - section in the Yocto Project Development Tasks Manual. - -
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- Components and Tools - - - The Yocto Project employs a collection of components and - tools used by the project itself, by project developers, - and by those using the Yocto Project. - These components and tools are open source projects and - metadata that are separate from the reference distribution - (Poky) - and the - OpenEmbedded build system. - Most of the components and tools are downloaded separately. - - - - This section provides brief overviews of the components and - tools associated with the Yocto Project. - - -
- Development Tools - - - The following list consists of tools that help you develop - images and applications using the Yocto Project: - - - CROPS: - CROPS - is an open source, cross-platform development framework - that leverages - Docker Containers. - CROPS provides an easily managed, extensible environment - that allows you to build binaries for a variety of - architectures on Windows, Linux and Mac OS X hosts. - - - devtool: - This command-line tool is available as part of the - extensible SDK (eSDK) and is its cornerstone. - You can use devtool to help build, - test, and package software within the eSDK. - You can use the tool to optionally integrate what you - build into an image built by the OpenEmbedded build - system. - - The devtool command employs - a number of sub-commands that allow you to add, modify, - and upgrade recipes. - As with the OpenEmbedded build system, "recipes" - represent software packages within - devtool. - When you use devtool add, a recipe - is automatically created. - When you use devtool modify, the - specified existing recipe is used in order to determine - where to get the source code and how to patch it. - In both cases, an environment is set up so that when - you build the recipe a source tree that is under your - control is used in order to allow you to make changes - to the source as desired. - By default, both new recipes and the source go into - a "workspace" directory under the eSDK. - The devtool upgrade command - updates an existing recipe so that you can build it - for an updated set of source files. - - You can read about the - devtool workflow in the Yocto - Project Application Development and Extensible - Software Development Kit (eSDK) Manual in the - "Using devtool in Your SDK Workflow'" - section. - - - Extensible Software Development Kit (eSDK): - The eSDK provides a cross-development toolchain and - libraries tailored to the contents of a specific image. - The eSDK makes it easy to add new applications and - libraries to an image, modify the source for an - existing component, test changes on the target - hardware, and integrate into the rest of the - OpenEmbedded build system. - The eSDK gives you a toolchain experience supplemented - with the powerful set of devtool - commands tailored for the Yocto Project environment. - - - For information on the eSDK, see the - Yocto Project Application Development and the Extensible Software Development Kit (eSDK) - Manual. - - - Toaster: - Toaster is a web interface to the Yocto Project - OpenEmbedded build system. - Toaster allows you to configure, run, and view - information about builds. - For information on Toaster, see the - Toaster User Manual. - - - -
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- Production Tools - - - The following list consists of tools that help production - related activities using the Yocto Project: - - - Auto Upgrade Helper: - This utility when used in conjunction with the - OpenEmbedded build system - (BitBake and OE-Core) automatically generates upgrades - for recipes that are based on new versions of the - recipes published upstream. - - - Recipe Reporting System: - The Recipe Reporting System tracks recipe versions - available for Yocto Project. - The main purpose of the system is to help you - manage the recipes you maintain and to offer a dynamic - overview of the project. - The Recipe Reporting System is built on top of the - OpenEmbedded Layer Index, - which is a website that indexes OpenEmbedded-Core - layers. - - - Patchwork: - Patchwork - is a fork of a project originally started by - OzLabs. - The project is a web-based tracking system designed - to streamline the process of bringing contributions - into a project. - The Yocto Project uses Patchwork as an organizational - tool to handle patches, which number in the thousands - for every release. - - - AutoBuilder: - AutoBuilder is a project that automates build tests - and quality assurance (QA). - By using the public AutoBuilder, anyone can determine - the status of the current "master" branch of Poky. - - AutoBuilder is based on - buildbot. - - - A goal of the Yocto Project is to lead the - open source industry with a project that automates - testing and QA procedures. - In doing so, the project encourages a development - community that publishes QA and test plans, publicly - demonstrates QA and test plans, and encourages - development of tools that automate and test and QA - procedures for the benefit of the development - community. - - You can learn more about the AutoBuilder used - by the Yocto Project - here. - - - Cross-Prelink: - Prelinking is the process of pre-computing the load - addresses and link tables generated by the dynamic - linker as compared to doing this at runtime. - Doing this ahead of time results in performance - improvements when the application is launched and - reduced memory usage for libraries shared by many - applications. - - Historically, cross-prelink is a variant of - prelink, which was conceived by - Jakub Jelínek - a number of years ago. - Both prelink and cross-prelink are maintained in the - same repository albeit on separate branches. - By providing an emulated runtime dynamic linker - (i.e. glibc-derived - ld.so emulation), the - cross-prelink project extends the prelink software's - ability to prelink a sysroot environment. - Additionally, the cross-prelink software enables the - ability to work in sysroot style environments. - - The dynamic linker determines standard load - address calculations based on a variety of factors - such as mapping addresses, library usage, and library - function conflicts. - The prelink tool uses this information, from the - dynamic linker, to determine unique load addresses - for executable and linkable format (ELF) binaries - that are shared libraries and dynamically linked. - The prelink tool modifies these ELF binaries with the - pre-computed information. - The result is faster loading and often lower memory - consumption because more of the library code can - be re-used from shared Copy-On-Write (COW) pages. - - - The original upstream prelink project only - supports running prelink on the end target device - due to the reliance on the target device's dynamic - linker. - This restriction causes issues when developing a - cross-compiled system. - The cross-prelink adds a synthesized dynamic loader - that runs on the host, thus permitting cross-prelinking - without ever having to run on a read-write target - filesystem. - - - Pseudo: - Pseudo is the Yocto Project implementation of - fakeroot, - which is used to run commands in an environment - that seemingly has root privileges. - - During a build, it can be necessary to perform - operations that require system administrator - privileges. - For example, file ownership or permissions might need - definition. - Pseudo is a tool that you can either use directly or - through the environment variable - LD_PRELOAD. - Either method allows these operations to succeed as - if system administrator privileges exist even - when they do not. - - You can read more about Pseudo in the - "Fakeroot and Pseudo" - section. - - - -
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- Open-Embedded Build System Components - - - The following list consists of components associated with the - OpenEmbedded build system: - - - BitBake: - BitBake is a core component of the Yocto Project and is - used by the OpenEmbedded build system to build images. - While BitBake is key to the build system, BitBake - is maintained separately from the Yocto Project. - - BitBake is a generic task execution engine that - allows shell and Python tasks to be run efficiently - and in parallel while working within complex inter-task - dependency constraints. - In short, BitBake is a build engine that works - through recipes written in a specific format in order - to perform sets of tasks. - - You can learn more about BitBake in the - BitBake User Manual. - - - OpenEmbedded-Core: - OpenEmbedded-Core (OE-Core) is a common layer of - metadata (i.e. recipes, classes, and associated files) - used by OpenEmbedded-derived systems, which includes - the Yocto Project. - The Yocto Project and the OpenEmbedded Project both - maintain the OpenEmbedded-Core. - You can find the OE-Core metadata in the Yocto Project - Source Repositories. - - - Historically, the Yocto Project integrated the - OE-Core metadata throughout the Yocto Project - source repository reference system (Poky). - After Yocto Project Version 1.0, the Yocto Project - and OpenEmbedded agreed to work together and share a - common core set of metadata (OE-Core), which contained - much of the functionality previously found in Poky. - This collaboration achieved a long-standing - OpenEmbedded objective for having a more tightly - controlled and quality-assured core. - The results also fit well with the Yocto Project - objective of achieving a smaller number of fully - featured tools as compared to many different ones. - - - Sharing a core set of metadata results in Poky - as an integration layer on top of OE-Core. - You can see that in this - figure. - The Yocto Project combines various components such as - BitBake, OE-Core, script "glue", and documentation - for its build system. - - - -
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- Reference Distribution (Poky) - - - Poky is the Yocto Project reference distribution. - It contains the - Open-Embedded build system - (BitBake and OE-Core) as well as a set of metadata to get you - started building your own distribution. - See the - figure in - "What is the Yocto Project?" section for an illustration - that shows Poky and its relationship with other parts of the - Yocto Project. - - To use the Yocto Project tools and components, you - can download (clone) Poky and use it - to bootstrap your own distribution. - - Poky does not contain binary files. - It is a working example of how to build your own custom - Linux distribution from source. - - You can read more about Poky in the - "Reference Embedded Distribution (Poky)" - section. - -
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- Packages for Finished Targets - - - The following lists components associated with packages - for finished targets: - - - Matchbox: - Matchbox is an Open Source, base environment for the - X Window System running on non-desktop, embedded - platforms such as handhelds, set-top boxes, kiosks, - and anything else for which screen space, input - mechanisms, or system resources are limited. - - Matchbox consists of a number of interchangeable - and optional applications that you can tailor to a - specific, non-desktop platform to enhance usability - in constrained environments. - - You can find the Matchbox source in the Yocto - Project - Source Repositories. - - - Opkg - Open PacKaGe management (opkg) is a lightweight - package management system based on the itsy package - (ipkg) management system. - Opkg is written in C and resembles Advanced Package - Tool (APT) and Debian Package (dpkg) in operation. - - - Opkg is intended for use on embedded Linux - devices and is used in this capacity in the - OpenEmbedded - and - OpenWrt - projects, as well as the Yocto Project. - - As best it can, opkg maintains backwards - compatibility with ipkg and conforms to a subset - of Debian's policy manual regarding control files. - - - - -
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- Archived Components - - - The Build Appliance is a virtual machine image that enables - you to build and boot a custom embedded Linux image with - the Yocto Project using a non-Linux development system. - - - - Historically, the Build Appliance was the second of three - methods by which you could use the Yocto Project on a system - that was not native to Linux. - - - Hob: - Hob, which is now deprecated and is no longer available - since the 2.1 release of the Yocto Project provided - a rudimentary, GUI-based interface to the Yocto - Project. - Toaster has fully replaced Hob. - - - Build Appliance: - Post Hob, the Build Appliance became available. - It was never recommended that you use the Build - Appliance as a day-to-day production development - environment with the Yocto Project. - Build Appliance was useful as a way to try out - development in the Yocto Project environment. - - - CROPS: - The final and best solution available now for - developing using the Yocto Project on a system - not native to Linux is with - CROPS. - - - -
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- Development Methods - - - The Yocto Project development environment usually involves a - Build Host - and target hardware. - You use the Build Host to build images and develop applications, - while you use the target hardware to test deployed software. - - - - This section provides an introduction to the choices or - development methods you have when setting up your Build Host. - Depending on the your particular workflow preference and the - type of operating system your Build Host runs, several choices - exist that allow you to use the Yocto Project. - - For additional detail about the Yocto Project development - environment, see the - "The Yocto Project Development Environment" - chapter. - - - - Native Linux Host: - By far the best option for a Build Host. - A system running Linux as its native operating system - allows you to develop software by directly using the - BitBake - tool. - You can accomplish all aspects of development from a - familiar shell of a supported Linux distribution. - - For information on how to set up a Build Host on - a system running Linux as its native operating system, - see the - "Setting Up a Native Linux Host" - section in the Yocto Project Development Tasks Manual. - - - CROss PlatformS (CROPS): - Typically, you use - CROPS, - which leverages - Docker Containers, - to set up a Build Host that is not running Linux (e.g. - Microsoft - Windows - or - macOS). - - You can, however, use CROPS on a Linux-based system. - - CROPS is an open source, cross-platform development - framework that provides an easily managed, extensible - environment for building binaries targeted for a variety - of architectures on Windows, macOS, or Linux hosts. - Once the Build Host is set up using CROPS, you can prepare - a shell environment to mimic that of a shell being used - on a system natively running Linux. - - For information on how to set up a Build Host with - CROPS, see the - "Setting Up to Use CROss PlatformS (CROPS)" - section in the Yocto Project Development Tasks Manual. - - - Windows Subsystem For Linux (WSLv2): - You may use Windows Subsystem For Linux v2 to set up a build - host using Windows 10. - - The Yocto Project is not compatible with WSLv1, it is - compatible but not officially supported nor validated - with WSLv2, if you still decide to use WSL please upgrade - to WSLv2. - - The Windows Subsystem For Linux allows Windows 10 to run a real - Linux kernel inside of a lightweight utility virtual - machine (VM) using virtualization technology. - For information on how to set up a Build Host with - WSLv2, see the - "Setting Up to Use Windows Subsystem For Linux" - section in the Yocto Project Development Tasks Manual. - - - Toaster: - Regardless of what your Build Host is running, you can - use Toaster to develop software using the Yocto Project. - Toaster is a web interface to the Yocto Project's - Open-Embedded build system. - The interface enables you to configure and run your - builds. - Information about builds is collected and stored in a - database. - You can use Toaster to configure and start builds on - multiple remote build servers. - - For information about and how to use Toaster, - see the - Toaster User Manual. - - - -
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- Reference Embedded Distribution (Poky) - - - "Poky", which is pronounced Pock-ee, is the - name of the Yocto Project's reference distribution or Reference OS - Kit. - Poky contains the - OpenEmbedded Build System - (BitBake and - OpenEmbedded-Core) - as well as a set of - metadata to get - you started building your own distro. - In other words, Poky is a base specification of the functionality - needed for a typical embedded system as well as the components - from the Yocto Project that allow you to build a distribution into - a usable binary image. - - - - Poky is a combined repository of BitBake, OpenEmbedded-Core - (which is found in meta), - meta-poky, - meta-yocto-bsp, and documentation provided - all together and known to work well together. - You can view these items that make up the Poky repository in the - Source Repositories. - - If you are interested in all the contents of the - poky Git repository, see the - "Top-Level Core Components" - section in the Yocto Project Reference Manual. - - - - - The following figure illustrates what generally comprises Poky: - - - - BitBake is a task executor and scheduler that is the heart of - the OpenEmbedded build system. - - - meta-poky, which is Poky-specific - metadata. - - - meta-yocto-bsp, which are Yocto - Project-specific Board Support Packages (BSPs). - - - OpenEmbedded-Core (OE-Core) metadata, which includes - shared configurations, global variable definitions, - shared classes, packaging, and recipes. - Classes define the encapsulation and inheritance of build - logic. - Recipes are the logical units of software and images - to be built. - - - Documentation, which contains the Yocto Project source - files used to make the set of user manuals. - - - - While Poky is a "complete" distribution specification and is - tested and put through QA, you cannot use it as a product - "out of the box" in its current form. - - - - - To use the Yocto Project tools, you can use Git to clone (download) - the Poky repository then use your local copy of the reference - distribution to bootstrap your own distribution. - - Poky does not contain binary files. - It is a working example of how to build your own custom Linux distribution - from source. - - - - - Poky has a regular, well established, six-month release cycle - under its own version. - Major releases occur at the same time major releases (point - releases) occur for the Yocto Project, which are typically in the - Spring and Fall. - For more information on the Yocto Project release schedule and - cadence, see the - "Yocto Project Releases and the Stable Release Process" - chapter in the Yocto Project Reference Manual. - - - - Much has been said about Poky being a "default configuration." - A default configuration provides a starting image footprint. - You can use Poky out of the box to create an image ranging from a - shell-accessible minimal image all the way up to a Linux - Standard Base-compliant image that uses a GNOME Mobile and - Embedded (GMAE) based reference user interface called Sato. - - - - One of the most powerful properties of Poky is that every aspect - of a build is controlled by the metadata. - You can use metadata to augment these base image types by - adding metadata - layers - that extend functionality. - These layers can provide, for example, an additional software - stack for an image type, add a board support package (BSP) for - additional hardware, or even create a new image type. - - - - Metadata is loosely grouped into configuration files or package - recipes. - A recipe is a collection of non-executable metadata used by - BitBake to set variables or define additional build-time tasks. - A recipe contains fields such as the recipe description, the recipe - version, the license of the package and the upstream source - repository. - A recipe might also indicate that the build process uses autotools, - make, distutils or any other build process, in which case the basic - functionality can be defined by the classes it inherits from - the OE-Core layer's class definitions in - ./meta/classes. - Within a recipe you can also define additional tasks as well as - task prerequisites. - Recipe syntax through BitBake also supports both - _prepend and _append - operators as a method of extending task functionality. - These operators inject code into the beginning or end of a task. - For information on these BitBake operators, see the - "Appending and Prepending (Override Style Syntax)" - section in the BitBake User's Manual. - -
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- The OpenEmbedded Build System Workflow - - - The - OpenEmbedded build system - uses a "workflow" to accomplish image and SDK generation. - The following figure overviews that workflow: - - Following is a brief summary of the "workflow": - - - Developers specify architecture, policies, patches and - configuration details. - - - The build system fetches and downloads the source code - from the specified location. - The build system supports standard methods such as tarballs - or source code repositories systems such as Git. - - - Once source code is downloaded, the build system extracts - the sources into a local work area where patches are - applied and common steps for configuring and compiling - the software are run. - - - The build system then installs the software into a - temporary staging area where the binary package format you - select (DEB, RPM, or IPK) is used to roll up the software. - - - Different QA and sanity checks run throughout entire - build process. - - - After the binaries are created, the build system - generates a binary package feed that is used to create - the final root file image. - - - The build system generates the file system image and a - customized Extensible SDK (eSDK) for application - development in parallel. - - - - - - For a very detailed look at this workflow, see the - "OpenEmbedded Build System Concepts" - section. - -
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- Some Basic Terms - - - It helps to understand some basic fundamental terms when - learning the Yocto Project. - Although a list of terms exists in the - "Yocto Project Terms" - section of the Yocto Project Reference Manual, this section - provides the definitions of some terms helpful for getting started: - - - Configuration Files: - Files that hold global definitions of variables, - user-defined variables, and hardware configuration - information. - These files tell the - Open-Embedded build system - what to build and what to put into the image to support a - particular platform. - - - Extensible Software Development Kit (eSDK): - A custom SDK for application developers. - This eSDK allows developers to incorporate their library - and programming changes back into the image to make - their code available to other application developers. - For information on the eSDK, see the - Yocto Project Application Development and the Extensible Software Development Kit (eSDK) - manual. - - - Layer: - A collection of related recipes. - Layers allow you to consolidate related metadata to - customize your build. - Layers also isolate information used when building - for multiple architectures. - Layers are hierarchical in their ability to override - previous specifications. - You can include any number of available layers from the - Yocto Project and customize the build by adding your - layers after them. - You can search the Layer Index for layers used within - Yocto Project. - - For more detailed information on layers, see the - "Understanding and Creating Layers" - section in the Yocto Project Development Tasks Manual. - For a discussion specifically on BSP Layers, see the - "BSP Layers" - section in the Yocto Project Board Support Packages (BSP) - Developer's Guide. - - - Metadata: - A key element of the Yocto Project is the Metadata that - is used to construct a Linux distribution and is contained - in the files that the OpenEmbedded build system parses - when building an image. - In general, Metadata includes recipes, configuration - files, and other information that refers to the build - instructions themselves, as well as the data used to - control what things get built and the effects of the - build. - Metadata also includes commands and data used to - indicate what versions of software are used, from - where they are obtained, and changes or additions to the - software itself (patches or auxiliary files) that - are used to fix bugs or customize the software for use - in a particular situation. - OpenEmbedded-Core is an important set of validated - metadata. - - - OpenEmbedded Build System: - The terms "BitBake" and "build system" are sometimes - used for the OpenEmbedded Build System. - - BitBake is a task scheduler and execution engine - that parses instructions (i.e. recipes) and configuration - data. - After a parsing phase, BitBake creates a dependency tree - to order the compilation, schedules the compilation of - the included code, and finally executes the building - of the specified custom Linux image (distribution). - BitBake is similar to the make - tool. - - During a build process, the build system tracks - dependencies and performs a native or cross-compilation - of the package. - As a first step in a cross-build setup, the framework - attempts to create a cross-compiler toolchain - (i.e. Extensible SDK) suited for the target platform. - - - OpenEmbedded-Core (OE-Core): - OE-Core is metadata comprised of foundation recipes, - classes, and associated files that are meant to be - common among many different OpenEmbedded-derived systems, - including the Yocto Project. - OE-Core is a curated subset of an original repository - developed by the OpenEmbedded community that has been - pared down into a smaller, core set of continuously - validated recipes. - The result is a tightly controlled and quality-assured - core set of recipes. - - You can see the Metadata in the - meta directory of the Yocto Project - Source Repositories. - - - Packages: - In the context of the Yocto Project, this term refers to a - recipe's packaged output produced by BitBake (i.e. a - "baked recipe"). - A package is generally the compiled binaries produced from the - recipe's sources. - You "bake" something by running it through BitBake. - - It is worth noting that the term "package" can, - in general, have subtle meanings. - For example, the packages referred to in the - "Required Packages for the Build Host" - section in the Yocto Project Reference Manual are compiled - binaries that, when installed, add functionality to your - Linux distribution. - - Another point worth noting is that historically within - the Yocto Project, recipes were referred to as packages - thus, - the existence of several BitBake variables that are seemingly - mis-named, - (e.g. PR, - PV, - and - PE). - - - Poky: - Poky is a reference embedded distribution and a reference - test configuration. - Poky provides the following: - - - A base-level functional distro used to illustrate - how to customize a distribution. - - - A means by which to test the Yocto Project - components (i.e. Poky is used to validate - the Yocto Project). - - - A vehicle through which you can download - the Yocto Project. - - - Poky is not a product level distro. - Rather, it is a good starting point for customization. - - Poky is an integration layer on top of OE-Core. - - - - Recipe: - The most common form of metadata. - A recipe contains a list of settings and tasks - (i.e. instructions) for building packages that are then - used to build the binary image. - A recipe describes where you get source code and which - patches to apply. - Recipes describe dependencies for libraries or for other - recipes as well as configuration and compilation options. - Related recipes are consolidated into a layer. - - - -
- - diff --git a/documentation/overview-manual/overview-manual.xml b/documentation/overview-manual/overview-manual.xml deleted file mode 100755 index 8021a2e95e..0000000000 --- a/documentation/overview-manual/overview-manual.xml +++ /dev/null @@ -1,130 +0,0 @@ - %poky; ] > - - - - - - - - - - - - - Yocto Project Overview and Concepts Manual - - - - - - &ORGNAME; - - &ORGEMAIL; - - - - - - 2.5 - May 2018 - The initial document released with the Yocto Project 2.5 Release. - - - 2.6 - November 2018 - Released with the Yocto Project 2.6 Release. - - - 2.7 - May 2019 - Released with the Yocto Project 2.7 Release. - - - 3.0 - October 2019 - Released with the Yocto Project 3.0 Release. - - - 3.1 - &REL_MONTH_YEAR; - Released with the Yocto Project 3.1 Release. - - - - - ©RIGHT_YEAR; - Linux Foundation - - - - - Permission is granted to copy, distribute and/or modify this document under - the terms of the - Creative Commons Attribution-Share Alike 2.0 UK: England & Wales as published by - Creative Commons. - - Manual Notes - - - This version of the - Yocto Project Overview and Concepts Manual - is for the &YOCTO_DOC_VERSION; release of the - Yocto Project. - To be sure you have the latest version of the manual - for this release, go to the - Yocto Project documentation page - and select the manual from that site. - Manuals from the site are more up-to-date than manuals - derived from the Yocto Project released TAR files. - - - If you located this manual through a web search, the - version of the manual might not be the one you want - (e.g. the search might have returned a manual much - older than the Yocto Project version with which you - are working). - You can see all Yocto Project major releases by - visiting the - Releases - page. - If you need a version of this manual for a different - Yocto Project release, visit the - Yocto Project documentation page - and select the manual set by using the - "ACTIVE RELEASES DOCUMENTATION" or "DOCUMENTS ARCHIVE" - pull-down menus. - - - - To report any inaccuracies or problems with this - (or any other Yocto Project) manual, send an email to - the Yocto Project documentation mailing list at - docs@lists.yoctoproject.org or - log into the freenode #yocto channel. - - - - - - - - - - - - - - - - - - -- cgit v1.2.3-54-g00ecf