%poky; ] > This chapter provides procedures related to getting set up to use the Yocto Project, working with Yocto Project source files, and building an image.

This section provides procedures to set up your development host to use the Yocto Project. You can use the Yocto Project on a native Linux development host or you can use CROPS, which leverages Docker Containers, to prepare any Linux, Mac, or Windows development host. Once your development host is set up to use the Yocto Project, further steps are necessary depending on what you want to accomplish. See the following references for information on how to prepare for Board Support Package (BSP) development, kernel development, and development using the Eclipse IDE: BSP Development: 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: See the "Preparing the Build Host to Work on the Kernel" section in the Yocto Project Linux Kernel Development Manual. Eclipse Development: See the "Developing Applications Using Eclipse" Chapter in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual.

Follow these steps to prepare a native Linux machine as your Yocto Project development host: Use a Supported Linux Distribution: You should have a reasonably current Linux-based host system. You will have the best results with a recent release of Fedora, openSUSE, Debian, Ubuntu, or CentOS as these releases are frequently tested against the Yocto Project and officially supported. For a list of the distributions under validation and their status, see the "Supported Linux Distributions" section in the Yocto Project Reference Manual and the wiki page at Distribution Support. Have Enough Free Memory: You should have at least 50 Gbytes of free disk space for building images. Meet Minimal Version Requirements: The OpenEmbedded build system should be able to run on any modern distribution that has the following versions for Git, tar, and Python. Git 1.8.3.1 or greater tar 1.27 or greater Python 3.4.0 or greater. If your build host does not meet any of these three listed version requirements, you can take steps to prepare the system so that you can still use the Yocto Project. See the "Required Git, tar, and Python Versions" section in the Yocto Project Reference Manual for information. Install Development Host Packages: Required development host packages vary depending on your build machine and what you want to do with the Yocto Project. Collectively, the number of required packages is large if you want to be able to cover all cases. For lists of required packages for all scenarios, see the "Required Packages for the Host Development System" section in the Yocto Project Reference Manual. Once you have completed the previous steps, you are ready to continue using a given development path on your native Linux machine. If you are going to use BitBake, see the "Cloning the poky Repository" section. If you are going to use the Extensible SDK, see the "Using the Extensible SDK" Chapter in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual. If you want to work on the kernel, see the Yocto Project Linux Kernel Development Manual. If you are going to use Toaster, see the "Setting Up and Using Toaster" section in the Toaster User Manual.

With CROPS, which leverages Docker Containers, you can create a Yocto Project development environment that is operating system agnostic. You can set up a container in which you can develop using the Yocto Project on a Windows, Mac, or Linux machine. Follow these general steps to prepare a Windows, Mac, or Linux machine as your Yocto Project development host: Go to the Docker Installation Site: Docker is a software container platform that you need to install on the host development machine. To start the installation process, see the Docker Installation site. Choose Your Docker Edition: Docker comes in several editions. For the Yocto Project, the stable community edition (i.e. "Docker CE Stable") is adequate. You can learn more about the Docker editions from the site. Go the Install Site for Your Platform: Click the link for the Docker edition associated with your development host machine's native software. For example, if your machine is running Microsoft Windows Version 10 and you want the Docker CE Stable edition, click that link under "Supported Platforms". Understand What You Need: The install page has pre-requisites your machine must meet. Be sure you read through this page and make sure your machine meets the requirements to run Docker. If your machine does not meet the requirements, the page has instructions to handle exceptions. For example, to run Docker on Windows 10, you must have the pro version of the operating system. If you have the home version, you need to install the Docker Toolbox. Another example is that a Windows machine needs to have Microsoft Hyper-V. If you have a legacy version of the the Microsoft operating system or for any other reason you do not have Microsoft Hyper-V, you would have to enter the BIOS and enable virtualization. Install the Software: Once you have understood all the pre-requisites, you can download and install the appropriate software. Follow the instructions for your specific machine and the type of the software you need to install. Optionally Orient Yourself With Dockers: If you are unfamiliar with Dockers and the container concept, you can learn more here - . You should be able to launch Docker or the Docker Toolbox and have a terminal shell on your development host. Set Up the Containers to Use the Yocto Project: Go to and follow the directions for your particular development host (i.e. Linux, Mac, or Windows). Once you complete the setup instructions for your machine, you have the Poky, Extensible SDK, and Toaster containers available. You can click those links from the page and learn more about using each of those containers. Once you have a container set up, everything is in place to develop just as if you were running on a native Linux machine. If you are going to use the Poky container, see the "Cloning the poky Repository" section. If you are going to use the Extensible SDK container, see the "Using the Extensible SDK" Chapter in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual. If you are going to use the Toaster container, see the "Setting Up and Using Toaster" section in the Toaster User Manual.

This section contains procedures related to locating and securing Yocto Project files. You establish and use these local files to work on projects. For concepts and introductory information about Git as it is used in the Yocto Project, see the "Git" section in the Yocto Project Overview Manual. For concepts on Yocto Project source repositories, see the "Yocto Project Source Repositories" section in the Yocto Project Overview Manual."

Working from a copy of the upstream Yocto Project Source Repositories is the preferred method for obtaining and using a Yocto Project release. You can view the Yocto Project Source Repositories at . In particular, you can find the poky repository at . Use the following procedure to locate the latest upstream copy of the poky Git repository: Access Repositories: Open a browser and go to to access the GUI-based interface into the Yocto Project source repositories. Select the Repository: Click on the repository in which you are interested (i.e. poky). Find the URL Used to Clone the Repository: At the bottom of the page, note the URL used to clone that repository (e.g. &YOCTO_GIT_URL;/poky). For information on cloning a repository, see the "Cloning the poky Repository" section.

Yocto Project maintains an Index of Releases area that contains related files that contribute to the Yocto Project. Rather than Git repositories, these files are tarballs that represent snapshots in time of a given component. The recommended method for accessing Yocto Project components is to use Git to clone the upstream repository and work from within that locally cloned repository. The procedure in this section exists should you desire a tarball snapshot of any given component. Access the Index of Releases: Open a browser and go to to access the Index of Releases. The list represents released components (e.g. eclipse-plugin, sato, and so on). The yocto directory contains the full array of released Poky tarballs. The poky directory in the Index of Releases was historically used for very early releases and exists now only for retroactive completeness. Select a Component: Click on any released component in which you are interested (e.g. yocto). Find the Tarball: Drill down to find the associated tarball. For example, click on yocto-&DISTRO; to view files associated with the Yocto Project &DISTRO; release (e.g. poky-&DISTRO_NAME_NO_CAP;-&POKYVERSION;.tar.bz2, which is the released Poky tarball). Download the Tarball: Click the tarball to download and save a snapshot of the given component.

The Yocto Project Website uses a "Downloads" area from which you can locate and download tarballs of any Yocto Project release. Rather than Git repositories, these files represent snapshot tarballs. The recommended method for accessing Yocto Project components is to use Git to clone a repository and work from within that local repository. The procedure in this section exists should you desire a tarball snapshot of any given component. Go to the Yocto Project Website: Open The Yocto Project Website in your browser. Get to the Downloads Area: Click the "Downloads" tab. Select the Type of Files: Click the type of files you want such as "Build System", "Tools", or "Board Support Packages (BSPs)". Locate and Download the Tarball: From the list of releases, locate the appropriate download link and download the files.

Yocto Project maintains an area for nightly builds that contains tarball releases at . These builds include Yocto Project releases, SDK installation scripts, and experimental builds. Should you ever want to access a nightly build of a particular Yocto Project component, use the following procedure: Access the Nightly Builds: Open a browser and go to to access the Nightly Builds. Select a Build: Click on any build by date in which you are interested. Find the Tarball: Drill down to find the associated tarball. Download the Tarball: Click the tarball to download and save a snapshot of the given component.

To use the Yocto Project, you need a release of the Yocto Project locally installed on your development system. The locally installed set of files is referred to as the Source Directory in the Yocto Project documentation. You create your Source Directory by using Git to clone a local copy of the upstream poky repository. The preferred method of getting the Yocto Project Source Directory set up is to clone the repository. Working from a copy of the upstream repository allows you to contribute back into the Yocto Project or simply work with the latest software on a development branch. Because Git maintains and creates an upstream repository with a complete history of changes and you are working with a local clone of that repository, you have access to all the Yocto Project development branches and tag names used in the upstream repository. Follow these steps to create a local version of the upstream poky Git repository. Set Your Directory: Be in the directory where you want to create your local copy of poky. Clone the Repository: The following command clones the repository and uses the default name "poky" for your local repository: $ git clone git://git.yoctoproject.org/poky Cloning into 'poky'... remote: Counting objects: 367178, done. remote: Compressing objects: 100% (88161/88161), done. remote: Total 367178 (delta 272761), reused 366942 (delta 272525) Receiving objects: 100% (367178/367178), 133.26 MiB | 6.40 MiB/s, done. Resolving deltas: 100% (272761/272761), done. Checking connectivity... done. Unless you specify a specific development branch or tag name, Git clones the "master" branch, which results in a snapshot of the latest development changes for "master". For information on how to check out a specific development branch or on how to check out a local branch based on a tag name, see the "Checking Out By Branch in Poky" and Checking Out By Tag in Poky", respectively. Once the repository is created, you can change to that directory and check its status. Here, the single "master" branch exists on your system and by default, it is checked out: $ cd ~/poky $ git status On branch master Your branch is up-to-date with 'origin/master'. nothing to commit, working directory clean $ git branch * master Your local repository of poky is identical to the upstream poky repository at the time from which it was cloned.

When you clone the upstream poky repository, you have access to all its development branches. Each development branch in a repository is unique as it forks off the "master" branch. To see and use the files of a particular development branch locally, you need to know the branch name and then specifically check out that development branch. Checking out an active development branch by branch name gives you a snapshot of that particular branch at the time you check it out. Further development on top of the branch that occurs after check it out can occur. Switch to the Poky Directory: If you have a local poky Git repository, switch to that directory. If you do not have the local copy of poky, see the "Cloning the poky Repository" section. Determine Existing Branch Names: $ git branch -a * master remotes/origin/1.1_M1 remotes/origin/1.1_M2 remotes/origin/1.1_M3 remotes/origin/1.1_M4 remotes/origin/1.2_M1 remotes/origin/1.2_M2 remotes/origin/1.2_M3 . . . remotes/origin/master-next remotes/origin/master-next2 remotes/origin/morty remotes/origin/pinky remotes/origin/purple remotes/origin/pyro remotes/origin/rocko Checkout the Branch: Checkout the development branch in which you want to work. For example, to access the files for the Yocto Project &DISTRO; Release (&DISTRO_NAME;), use the following command: $ git checkout -b &DISTRO_NAME_NO_CAP; origin/&DISTRO_NAME_NO_CAP; Branch &DISTRO_NAME_NO_CAP; set up to track remote branch &DISTRO_NAME_NO_CAP; from origin. Switched to a new branch '&DISTRO_NAME_NO_CAP;' The previous command checks out the "&DISTRO_NAME_NO_CAP;" development branch and reports that the branch is tracking the upstream "origin/&DISTRO_NAME_NO_CAP;" branch. The following command displays the branches that are now part of your local poky repository. The asterisk character indicates the branch that is currently checked out for work: $ git branch master * &DISTRO_NAME_NO_CAP;

Similar to branches, the upstream repository uses tags to mark specific commits associated with significant points in a development branch (i.e. a release point or stage of a release). You might want to set up a local branch based on one of those points in the repository. The process is similar to checking out by branch name except you use tag names. Checking out a branch based on a tag gives you a stable set of files not affected by development on the branch above the tag. Switch to the Poky Directory: If you have a local poky Git repository, switch to that directory. If you do not have the local copy of poky, see the "Cloning the poky Repository" section. Fetch the Tag Names: To checkout the branch based on a tag name, you need to fetch the upstream tags into your local repository: $ git fetch --tags $ List the Tag Names: You can list the tag names now: $ git tag 1.1_M1.final 1.1_M1.rc1 1.1_M1.rc2 1.1_M2.final 1.1_M2.rc1 . . . yocto-2.2 yocto-2.2.1 yocto-2.3 yocto-2.3.1 yocto-2.4 yocto_1.5_M5.rc8 Checkout the Branch: $ git checkout tags/&DISTRO; -b my_yocto_&DISTRO; Switched to a new branch 'my_yocto_&DISTRO;' $ git branch master * my_yocto_&DISTRO; The previous command creates and checks out a local branch named "my_yocto_&DISTRO;", which is based on the commit in the upstream poky repository that has the same tag. In this example, the files you have available locally as a result of the checkout command are a snapshot of the "&DISTRO_NAME_NO_CAP;" development branch at the point where Yocto Project &DISTRO; was released.

In the development environment, you need to build an image whenever you change hardware support, add or change system libraries, or add or change services that have dependencies. Several methods exist that allow you to build an image within the Yocto Project. This section shows you how to build an image using BitBake from a Linux host. For information on how to build an image using Toaster, see the Toaster Manual. For information on how to use devtool to build images, see the "Using devtool in Your SDK Workflow" section in the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual. For a practical example on how to build an image using the OpenEmbedded build system, see the "Building Images" section of the Yocto Project Quick Start. The build process creates an entire Linux distribution from source and places it in your Build Directory under tmp/deploy/images. For detailed information on the build process using BitBake, see the "Images" section in the Yocto Project Overview Manual. The following figure and list overviews the build process: Set up Your Host Development System to Support Development Using the Yocto Project: See the "Setting Up to Use the Yocto Project" section in the Yocto Project Quick Start for options on how to get a build host ready to use the Yocto Project. Initialize the Build Environment: Initialize the build environment by sourcing the build environment script (i.e. &OE_INIT_FILE;): $ source &OE_INIT_FILE; [build_dir] When you use the initialization script, the OpenEmbedded build system uses build as the default Build Directory in your current work directory. You can use a build_dir argument with the script to specify a different build directory. A common practice is to use a different Build Directory for different targets. For example, ~/build/x86 for a qemux86 target, and ~/build/arm for a qemuarm target. Make Sure Your local.conf File is Correct: Ensure the conf/local.conf configuration file, which is found in the Build Directory, is set up how you want it. This file defines many aspects of the build environment including the target machine architecture through the MACHINE variable, the packaging format used during the build (PACKAGE_CLASSES), and a centralized tarball download directory through the DL_DIR variable. Build the Image: Build the image using the bitbake command: $ bitbake target For information on BitBake, see the BitBake User Manual. The target is the name of the recipe you want to build. Common targets are the images in meta/recipes-core/images, meta/recipes-sato/images, etc. all found in the Source Directory. Or, the target can be the name of a recipe for a specific piece of software such as BusyBox. For more details about the images the OpenEmbedded build system supports, see the "Images" chapter in the Yocto Project Reference Manual. As an example, the following command builds the core-image-minimal image: $ bitbake core-image-minimal Once an image has been built, it often needs to be installed. The images and kernels built by the OpenEmbedded build system are placed in the Build Directory in tmp/deploy/images. For information on how to run pre-built images such as qemux86 and qemuarm, see the Yocto Project Application Development and the Extensible Software Development Kit (eSDK) manual. For information about how to install these images, see the documentation for your particular board or machine.

Build time can be an issue. By default, the build system uses simple controls to try and maximize build efficiency. In general, the default settings for all the following variables result in the most efficient build times when dealing with single socket systems (i.e. a single CPU). If you have multiple CPUs, you might try increasing the default values to gain more speed. See the descriptions in the glossary for each variable for more information: BB_NUMBER_THREADS: The maximum number of threads BitBake simultaneously executes. BB_NUMBER_PARSE_THREADS: The number of threads BitBake uses during parsing. PARALLEL_MAKE: Extra options passed to the make command during the do_compile task in order to specify parallel compilation on the local build host. PARALLEL_MAKEINST: Extra options passed to the make command during the do_install task in order to specify parallel installation on the local build host. As mentioned, these variables all scale to the number of processor cores available on the build system. For single socket systems, this auto-scaling ensures that the build system fundamentally takes advantage of potential parallel operations during the build based on the build machine's capabilities. Following are additional factors that can affect build speed: File system type: The file system type that the build is being performed on can also influence performance. Using ext4 is recommended as compared to ext2 and ext3 due to ext4 improved features such as extents. Disabling the updating of access time using noatime: The noatime mount option prevents the build system from updating file and directory access times. Setting a longer commit: Using the "commit=" mount option increases the interval in seconds between disk cache writes. Changing this interval from the five second default to something longer increases the risk of data loss but decreases the need to write to the disk, thus increasing the build performance. Choosing the packaging backend: Of the available packaging backends, IPK is the fastest. Additionally, selecting a singular packaging backend also helps. Using tmpfs for TMPDIR as a temporary file system: While this can help speed up the build, the benefits are limited due to the compiler using -pipe. The build system goes to some lengths to avoid sync() calls into the file system on the principle that if there was a significant failure, the Build Directory contents could easily be rebuilt. Inheriting the rm_work class: Inheriting this class has shown to speed up builds due to significantly lower amounts of data stored in the data cache as well as on disk. Inheriting this class also makes cleanup of TMPDIR faster, at the expense of being easily able to dive into the source code. File system maintainers have recommended that the fastest way to clean up large numbers of files is to reformat partitions rather than delete files due to the linear nature of partitions. This, of course, assumes you structure the disk partitions and file systems in a way that this is practical. Aside from the previous list, you should keep some trade offs in mind that can help you speed up the build: Remove items from DISTRO_FEATURES that you might not need. Exclude debug symbols and other debug information: If you do not need these symbols and other debug information, disabling the *-dbg package generation can speed up the build. You can disable this generation by setting the INHIBIT_PACKAGE_DEBUG_SPLIT variable to "1". Disable static library generation for recipes derived from autoconf or libtool: Following is an example showing how to disable static libraries and still provide an override to handle exceptions: STATICLIBCONF = "--disable-static" STATICLIBCONF_sqlite3-native = "" EXTRA_OECONF += "${STATICLIBCONF}" Some recipes need static libraries in order to work correctly (e.g. pseudo-native needs sqlite3-native). Overrides, as in the previous example, account for these kinds of exceptions. Some packages have packaging code that assumes the presence of the static libraries. If so, you might need to exclude them as well.