# Yocto Project Quick Build

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## Welcome!

Welcome! This short document steps you through the process for a typical image build using the Yocto Project. The document also introduces how to configure a build for specific hardware. You will use Yocto Project to build a reference embedded OS called Poky.

Notes

- The examples in this paper assume you are using a native Linux system running a recent Ubuntu Linux distribution. If the machine you want to use Yocto Project on to build an image (build host) is not a native Linux system, you can still perform these steps by using CROss PlatformS (CROPS) and setting up a Poky container. See the Setting Up to Use CROss PlatformS (CROPS)" section in the Yocto Project Development Tasks Manual for more information.

- You cannot use a build host that is using the Windows Subsystem for Linux (WSL). The Yocto Project is not compatible with WSL.

If you want more conceptual or background information on the Yocto Project, see the Yocto Project Overview and Concepts Manual.

## Compatible Linux Distribution

Make sure your build host meets the following requirements:

- 50 Gbytes of free disk space

- Runs a supported Linux distribution (i.e. recent releases of Fedora, openSUSE, CentOS, Debian, or Ubuntu). For a list of Linux distributions that support the Yocto Project, see the "Supported Linux Distributions" section in the Yocto Project Reference Manual. For detailed information on preparing your build host, see the "Preparing the Build Host" section in the Yocto Project Development Tasks Manual.

- - 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.

## Build Host Packages

You must install essential host packages on your build host. The following command installs the host packages based on an Ubuntu distribution:

For host package requirements on all supported Linux distributions, see the "Required Packages for the Build Host" section in the Yocto Project Reference Manual.

         $ sudo apt-get install &UBUNTU_HOST_PACKAGES_ESSENTIAL; libsdl1.2-dev xterm

## Use Git to Clone Poky

Once you complete the setup instructions for your machine, you need to get a copy of the Poky repository on your build host. Use the following commands to clone the Poky repository and then checkout the &DISTRO_REL_TAG; release:

         $ git clone git://git.yoctoproject.org/poky
         Cloning into 'poky'...
         remote: Counting objects: 361782, done.
         remote: Compressing objects: 100% (87100/87100), done.
         remote: Total 361782 (delta 268619), reused 361439 (delta 268277)
         Receiving objects: 100% (361782/361782), 131.94 MiB | 6.88 MiB/s, done.
         Resolving deltas: 100% (268619/268619), done.
         Checking connectivity... done.
         $ git checkout tags/yocto-2.5 -b my-yocto-2.5

The previous Git checkout command creates a local branch named my-&DISTRO_REL_TAG;. The files available to you in that branch exactly match the repository's files in the "&DISTRO_NAME_NO_CAP;" development branch at the time of the Yocto Project &DISTRO; release.

For more options and information about accessing Yocto Project related repositories, see the "Locating Yocto Project Source Files" section in the Yocto Project Development Tasks Manual.

## Building Your Image

Use the following steps to build your image. The build process creates an entire Linux distribution, including the toolchain, from source.

- If you are working behind a firewall and your build host is not set up for proxies, you could encounter problems with the build process when fetching source code (e.g. fetcher failures or Git failures).

- If you do not know your proxy settings, consult your local network infrastructure resources and get that information. A good starting point could also be to check your web browser settings. Finally, you can find more information on the "Working Behind a Network Proxy" page of the Yocto Project Wiki.

1. Initialize the Build Environment: Run the `&OE_INIT_FILE;` environment setup script to define Yocto Project's build environment on your build host.

            $ source &OE_INIT_FILE;

   Among other things, the script creates the Build Directory, which is `build` in this case and is located in the Source Directory. After the script runs, your current working directory is set to the Build Directory. Later, when the build completes, the Build Directory contains all the files created during the build.

2. Examine Your Local Configuration File: When you set up the build environment, a local configuration file named `local.conf` becomes available in a `conf` subdirectory of the Build Directory. For this example, the defaults are set to build for a `qemux86` target, which is suitable for emulation. The package manager used is set to the RPM package manager.

   You can significantly speed up your build and guard against fetcher failures by using mirrors. To use mirrors, add these lines to your `local.conf` file in the Build directory:

            SSTATE_MIRRORS = "\
            file://.* http://sstate.yoctoproject.org/dev/PATH;downloadfilename=PATH \n \
            file://.* http://sstate.yoctoproject.org/&YOCTO_DOC_VERSION_MINUS_ONE;/PATH;downloadfilename=PATH \n \
            file://.* http://sstate.yoctoproject.org/&YOCTO_DOC_VERSION;/PATH;downloadfilename=PATH \n \
            "

   The previous examples showed how to add sstate paths for Yocto Project &YOCTO_DOC_VERSION_MINUS_ONE;, &YOCTO_DOC_VERSION;, and a development area. For a complete index of sstate locations, see .

3. Start the Build: Continue with the following command to build an OS image for the target, which is `core-image-sato` in this example:

            $ bitbake core-image-sato

   For information on using the `bitbake` command, see the "BitBake" section in the Yocto Project Overview and Concepts Manual, or see the "BitBake Command" section in the BitBake User Manual.

4. Simulate Your Image Using QEMU: Once this particular image is built, you can start QEMU, which is a Quick EMUlator that ships with the Yocto Project:

            $ runqemu qemux86

   If you want to learn more about running QEMU, see the "Using the Quick EMUlator (QEMU)" chapter in the Yocto Project Development Tasks Manual.

5. Exit QEMU: Exit QEMU by either clicking on the shutdown icon or by typing `Ctrl-C` in the QEMU transcript window from which you evoked QEMU.

## Customizing Your Build for Specific Hardware

So far, all you have done is quickly built an image suitable for emulation only. This section shows you how to customize your build for specific hardware by adding a hardware layer into the Yocto Project development environment.

In general, layers are repositories that contain related sets of instructions and configurations that tell the Yocto Project what to do. Isolating related metadata into functionally specific layers facilitates modular development and makes it easier to reuse the layer metadata.

By convention, layer names start with the string "meta-".

Follow these steps to add a hardware layer:

1. Find a Layer: Lots of hardware layers exist. The Yocto Project Source Repositories has many hardware layers. This example adds the meta-altera hardware layer.

2. Clone the Layer Use Git to make a local copy of the layer on your machine. You can put the copy in the top level of the copy of the Poky repository created earlier:

            $ cd ~/poky
            $ git clone https://github.com/kraj/meta-altera.git
            Cloning into 'meta-altera'...
            remote: Counting objects: 25170, done.
            remote: Compressing objects: 100% (350/350), done.
            remote: Total 25170 (delta 645), reused 719 (delta 538), pack-reused 24219
            Receiving objects: 100% (25170/25170), 41.02 MiB | 1.64 MiB/s, done.
            Resolving deltas: 100% (13385/13385), done.
            Checking connectivity... done.

   The hardware layer now exists with other layers inside the Poky reference repository on your build host as `meta-altera` and contains all the metadata needed to support hardware from Altera, which is owned by Intel.

3. Change the Configuration to Build for a Specific Machine: The `MACHINE` variable in the `local.conf` file specifies the machine for the build. For this example, set the `MACHINE` variable to "cyclone5". These configurations are used: .

   See the "Examine Your Local Configuration File" step earlier for more information on configuring the build.

4. Add Your Layer to the Layer Configuration File: Before you can use a layer during a build, you must add it to your `bblayers.conf` file, which is found in the Build Directory's `conf` directory.

   Use the `bitbake-layers add-layer` command to add the layer to the configuration file:

            $ cd ~/poky/build
            $ bitbake-layers add-layer ../meta-altera
            NOTE: Starting bitbake server...
            Parsing recipes: 100% |##################################################################| Time: 0:00:32
            Parsing of 918 .bb files complete (0 cached, 918 parsed). 1401 targets, 123 skipped, 0 masked, 0 errors.

   You can find more information on adding layers in the "Adding a Layer Using the `bitbake-layers` Script" section.

Completing these steps has added the `meta-altera` layer to your Yocto Project development environment and configured it to build for the "cyclone5" machine.
The previous steps are for demonstration purposes only. If you were to attempt to build an image for the "cyclone5" build, you should read the Altera `README`.

## Creating Your Own General Layer

Maybe you have an application or specific set of behaviors you need to isolate. You can create your own general layer using the `bitbake-layers create-layer` command. The tool automates layer creation by setting up a subdirectory with a `layer.conf` configuration file, a `recipes-example` subdirectory that contains an `example.bb` recipe, a licensing file, and a `README`.

The following commands run the tool to create a layer named `meta-mylayer` in the `poky` directory:

         $ cd ~/poky
         $ bitbake-layers create-layer meta-mylayer
         NOTE: Starting bitbake server...
         Add your new layer with 'bitbake-layers add-layer meta-mylayer'

For more information on layers and how to create them, see the "Creating a General Layer Using the `bitbake-layers` Script" section in the Yocto Project Development Tasks Manual.

## Where To Go Next

Now that you have experienced using the Yocto Project, you might be asking yourself "What now?" The Yocto Project has many sources of information including the website, wiki pages, and user manuals:

- Website: The Yocto Project Website provides background information, the latest builds, breaking news, full development documentation, and access to a rich Yocto Project Development Community into which you can tap.

- Developer Screencast: The Getting Started with the Yocto Project - New Developer Screencast Tutorial provides a 30-minute video created for users unfamiliar with the Yocto Project but familiar with Linux build hosts. While this screencast is somewhat dated, the introductory and fundamental concepts are useful for the beginner.

- Yocto Project Overview and Concepts Manual: The Yocto Project Overview and Concepts Manual is a great place to start to learn about the Yocto Project. This manual introduces you to the Yocto Project and its development environment. The manual also provides conceptual information for various aspects of the Yocto Project.

- Yocto Project Wiki: The Yocto Project Wiki provides additional information on where to go next when ramping up with the Yocto Project, release information, project planning, and QA information.

- Yocto Project Mailing Lists: Related mailing lists provide a forum for discussion, patch submission and announcements. Several mailing lists exist and are grouped according to areas of concern. See the "Mailing lists" section in the Yocto Project Reference Manual for a complete list of Yocto Project mailing lists.

- Comprehensive List of Links and Other Documentation: The "Links and Related Documentation" section in the Yocto Project Reference Manual provides a comprehensive list of all related links and other user documentation.