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Multiple Repository Management

This page introduces basic concepts related to west and its multiple repository management features, and gives an overview of the associated commands. See History and Motivation and Zephyr issue #6770 for additional discussion, rationale, and motivation.


West’s multi-repo commands are meant to augment Git in minor ways for multi-repo work, not to replace it. For tasks that only operate on one repository, just use plain Git commands.


West’s built-in commands allow you to work with projects composed of multiple Git repositories installed under a common parent directory, which we call a west workspace (before west 0.7, this was called a west installation). This works similarly to Git Submodules and Google’s repo.

A west workspace is the result of running the west init command, which is described in more detail below. For upstream Zephyr, the workspace looks like this:

zephyrproject/                 # west topdir
├── .west/
│   └── config
├── zephyr/                    # .git/     │
│   ├── west.yml               # manifest  │ never modified by west
│   └── [... other files ...]              │
├── modules/
│   └── lib/
│       └── tinycbor/          # .git/ project
├── net-tools/                 # .git/ project
└── [ ... other projects ...]

Above, zephyrproject is the name of the west workspace’s root directory. This name is just an example – it could be anything, like z, my-zephyr-workspace, etc. The file .west/config is the workspace’s local configuration file.

Every west workspace contains exactly one manifest repository, which is a Git repository containing a file named west.yml, which is the west manifest. The location of the manifest repository is given by the manifest.path configuration option in the local configuration file. The manifest file, along with west’s configuration files, controls the workspace’s behavior. For upstream Zephyr, zephyr is the manifest repository, but you can configure west to use any Git repository in the workspace as the manifest repository. The only requirement is that it contains a valid manifest file. See West Manifests for more details on what this means.

Both of the tinycbor and net-tools directories are projects managed by west, and configured in the manifest file. A west workspace can contain arbitrarily many projects. As shown above, projects can be located anywhere in the workspace. They don’t have to be subdirectories of the manifest directory, and they can be inside of arbitrary subdirectories inside the workspace’s root directory. By default, the Zephyr build system uses west to get the locations of all the projects in the workspace, so any code they contain can be used by applications. This behavior can be overridden using the ZEPHYR_MODULES CMake variable; see Modules (External projects) for details.

Finally, any repository managed by a west workspace can contain extension commands, which are extra west commands provided by that project. This includes the manifest repository and any project repository.

Topologies supported

The following are example source code topologies supported by west.

  • T1: star topology, zephyr is the manifest repository

  • T2: star topology, a Zephyr application is the manifest repository

  • T3: forest topology, freestanding manifest repository

T1: Star topology, zephyr is the manifest repository

  • The zephyr repository acts as the central repository and specifies its Modules (External projects) in its west.yml

  • Analogy with existing mechanisms: Git submodules with zephyr as the super-project

This is the default. See Introduction for how mainline Zephyr is an example of this topology.

T2: Star topology, application is the manifest repository

  • Useful for those focused on a single application

  • A repository containing a Zephyr application acts as the central repository and names other projects required to build it in its west.yml. This includes the zephyr repository and any modules.

  • Analogy with existing mechanisms: Git submodules with the application as the super-project, zephyr and other projects as submodules

A workspace using this topology looks like this:

├── application/         # .git/     │
│   ├── CMakeLists.txt               │
│   ├── prj.conf                     │  never modified by west
│   ├── src/                         │
│   │   └── main.c                   │
│   └── west.yml         # main manifest with optional import(s) and override(s)
│                                    │
├── modules/
│   └── lib/
│       └── tinycbor/    # .git/ project from either the main manifest or some import.
└── zephyr/              # .git/ project
    └── west.yml         # This can be partially imported with lower precedence or ignored.
                         # Only the 'manifest-rev' version can be imported.

Here is an example application/west.yml which uses Manifest Imports, available since west 0.7, to import Zephyr v2.2.0 and its modules into the application manifest file:

# Example T2 west.yml, using manifest imports.
    - name: zephyrproject-rtos
    - name: zephyr
      remote: zephyrproject-rtos
      revision: v2.2.0
      import: true
    path: application

You can still selectively “override” individual Zephyr modules if you use import: in this way; see Example 1.3: Downstream of a Zephyr release, with module fork for an example.

Another way to do the same thing is to copy/paste zephyr/west.yml to application/west.yml, adding an entry for the zephyr project itself, like this:

# Equivalent to the above, but with manually maintained Zephyr modules.
    - name: zephyrproject-rtos
    remote: zephyrproject-rtos
    - name: zephyr
      revision: v2.2.0
      west-commands: scripts/west-commands.yml
    - name: net-tools
      revision: some-sha-goes-here
      path: tools/net-tools
    # ... other Zephyr modules go here ...
    path: application

(The west-commands is there for Building, Flashing and Debugging and other Zephyr-specific Extensions. It’s not necessary when using import.)

The main advantage to using import is not having to track the revisions of imported projects separately. In the above example, using import means Zephyr’s module versions are automatically determined from the zephyr/west.yml revision, instead of having to be copy/pasted (and maintained) on their own.

T3: Forest topology

  • Useful for those supporting multiple independent applications or downstream distributions with no “central” repository

  • A dedicated manifest repository which contains no Zephyr source code, and specifies a list of projects all at the same “level”

  • Analogy with existing mechanisms: Google repo-based source distribution

A workspace using this topology looks like this:

├── app1/               # .git/ project
│   ├── CMakeLists.txt
│   ├── prj.conf
│   └── src/
│       └── main.c
├── app2/               # .git/ project
│   ├── CMakeLists.txt
│   ├── prj.conf
│   └── src/
│       └── main.c
├── manifest-repo/      # .git/ never modified by west
│   └── west.yml        # main manifest with optional import(s) and override(s)
├── modules/
│   └── lib/
│       └── tinycbor/   # .git/ project from either the main manifest or
│                       #       frome some import
└── zephyr/             # .git/ project
    └── west.yml        # This can be partially imported with lower precedence or ignored.
                        # Only the 'manifest-rev' version can be imported.

Here is an example T3 manifest-repo/west.yml which uses Manifest Imports, available since west 0.7, to import Zephyr v2.2.0 and its modules, then add the app1 and app2 projects:

    - name: zephyrproject-rtos
    - name: your-git-server
    remote: your-git-server
    - name: zephyr
      remote: zephyrproject-rtos
      revision: v2.2.0
      import: true
    - name: app1
      revision: SOME_SHA_OR_BRANCH_OR_TAG
    - name: app2
    path: manifest-repo

You can also do this “by hand” by copy/pasting zephyr/west.yml as shown above for the T2 topology, with the same caveats.

West Structure

West’s code is distributed via PyPI in a Python package named west. See West APIs for API documentation.

This distribution also includes a launcher executable, also named west. When west is installed, the launcher is placed by pip3 somewhere in the user’s filesystem (exactly where depends on the operating system, but should be on the PATH environment variable). This launcher is the command-line entry point.

The manifest-rev branch

West creates a branch named manifest-rev in each project, pointing to the commit the project’s revision resolves to. The branch is updated whenever project data is fetched by west update. Other multi-repo commands also use manifest-rev as a reference for the upstream revision as of the most recent update. See Multi-Repo Commands, below, for more information.

manifest-rev is a normal Git branch, but if you delete or otherwise modify it, west will recreate and/or reset it as if with git reset --hard on the next update (though git update-ref is used internally). For this reason, it is normally a bad idea to modify it yourself. manifest-rev was added to allow SHAs as project revisions in the manifest, and to give a consistent reference for the current upstream revision regardless of how the manifest changes over time.


West does not create a manifest-rev branch in the manifest repository, since west does not manage the manifest repository’s branches or revisions.

Multi-Repo Commands

This section gives a quick overview of the multi-repo commands, split up by functionality. Some commands loosely mimic the corresponding Git command, but in a multi-repo context (e.g. west diff shows local changes on all repositories).

Project arguments can be the names of projects in the manifest, or (as fallback) paths to them. Omitting project arguments to commands which accept a list of projects (such as west list, west forall, etc.) usually defaults to using all projects in the manifest file plus the manifest repository itself.

For help on individual commands, run west <command> -h (e.g. west diff -h).

Main Commands

The west init and west update multi-repo commands are the most important to understand.

  • west init [-l] [-m URL] [--mr REVISION] [PATH]: create a west workspace in directory PATH (i.e. .west etc. will be created there). If the PATH argument is not given, the current working directory is used. This command does not clone any of the projects in the manifest; that is done the next time west update is run.

    This command can be invoked in two ways:

    1. If you already have a local clone of the zephyr repository and want to create a west workspace around it, you can use the -l switch to pass its path to west, as in: west init -l path/to/zephyr. This is the only reason to use -l.

    2. Otherwise, omit -l to create a new workspace from a remote manifest repository. You can give the manifest URL using the -m switch, and its revision using --mr. For example, invoking west with: west init -m --mr v1.15.0 would clone the upstream official zephyr repository at the tagged release v1.15.0 (-m defaults to, and the -mr default is overridden to v1.15.0).

  • west update [--fetch {always,smart}] [--rebase] [--keep-descendants] [PROJECT ...]: clone and update the specified projects based on the current west manifest.

    By default, this command:

    1. Parses the manifest file, west.yml

    2. Clones any project repositories that are not already present locally

    3. Fetches any project revisions in the manifest file which are not already pulled from the remote

    4. Sets each project’s manifest-rev branch to the current manifest revision

    5. Checks out those revisions in local working trees

    To operate on a subset of projects only, specify them using the PROJECT positional arguments, which can be either project names as given in the manifest file, or paths to the local project clones.

    To force this command to fetch from project remotes even if the revisions appear to be available locally, either use --fetch always or set the update.fetch configuration option to "always".

    For safety, west update uses git checkout --detach to check out a detached HEAD at the manifest revision for each updated project, leaving behind any branches which were already checked out. This is typically a safe operation that will not modify any of your local branches. See the help for the --rebase / -r and --keep-descendants / -k options for ways to influence this.

Miscellaneous Commands

West has a few more commands for managing the multi-repo, which are briefly discussed here. Run west <command> -h for detailed help.

  • west forall -c COMMAND [PROJECT ...]: Runs the shell command COMMAND within the top-level repository directory of each of the specified projects (default: all cloned projects). If COMMAND consists of more than one word, it must be quoted to prevent it from being split up by the shell.

    To run an arbitrary Git command in each project, use something like west forall -c 'git <command> --options'. Note that west forall can be used to run any command, though, not just Git commands.

  • west help <command>: this is equivalent to west <command> -h.

  • west list [-f FORMAT] [PROJECT ...]: Lists project information from the manifest file, such as URL, revision, path, etc. The printed information can be controlled using the -f option.

  • west manifest: Manipulates manifest files. See Manifest Command.

  • west manifest --validate: Ensure the current manifest file is well-formed. Print information about what’s wrong and fail the process in case of error.

  • west diff [PROJECT ...]: Runs a multi-repo git diff for the specified projects.

  • west status [PROJECT ...]: Like west diff, for running git status.

  • west topdir: Prints the top directory of the west workspace.

Private repositories

You can use west to fetch from private repositories. There is nothing west-specific about this.

The west update command essentially runs git fetch YOUR_PROJECT_URL when a project’s manifest-rev branch must be updated to a newly fetched commit. It’s up to your environment to make sure the fetch succeeds.

You can either enter the password manually or use any of the credential helpers built in to Git. Since Git has credential storage built in, there is no need for a west-specific feature.

The following sections cover common cases for running west update without having to enter your password, as well as how to troubleshoot issues.

Fetching via HTTPS

On Windows when fetching from GitHub, recent versions of Git prompt you for your GitHub password in a graphical window once, then store it for future use (in a default installation). Passwordless fetching from GitHub should therefore work “out of the box” on Windows after you have done it once.

In general, you can store your credentials on disk using the “store” git credential helper. See the git-credential-store manual page for details.

To use this helper for all the repositories in your workspace, run:

west forall -c "git config credential.helper store"

To use this helper on just the projects foo and bar, run:

west forall -c "git config credential.helper store" foo bar

To use this helper by default on your computer, run:

git config --global credential.helper store

On GitHub, you can set up a personal access token to use in place of your account password. (This may be required if your account has two-factor authentication enabled, and may be preferable to storing your account password in plain text even if two-factor authentication is disabed.)

If you don’t want to store any credentials on the file system, you can store them in memory temporarily using git-credential-cache instead.

Fetching via SSH

If your SSH key has no password, fetching should just work. If it does have a password, you can avoid entering it manually every time using ssh-agent.

On GitHub, see Connecting to GitHub with SSH for details on configuration and key creation.


One good way to troubleshoot fetching issues is to run west update in verbose mode, like this:

west -v update

The output includes Git commands run by west and their outputs. Look for something like this:

=== updating your_project (path/to/your/project):
west.manifest: your_project: checking if cloned
[...other west.manifest logs...]
--- your_project: fetching, need revision SOME_SHA
west.manifest: running 'git fetch ... ...' in /some/directory

The git fetch command example in the last line above is what needs to succeed. Go to /some/directory, copy/paste and run the entire git fetch command, then debug from there using the documentation for your credential storage helper.

If you can get the git fetch command to run successfully without prompting for a password when you run it directly, you will be able to run west update without entering your password in that same shell.