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 installation. This works similarly to Git Submodules and Google’s repo.

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

├── .west
│   └── config
├── zephyr
│   ├── west.yml
│   └── [... other files ...]
├── modules
│   └── lib
│       └── tinycbor
├── net-tools
└── [ ... other projects ...]

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

Every west installation 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 installation’s behavior. For upstream Zephyr, zephyr is the manifest repository, but you can configure west to use any Git repository in the installation 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 installation can contain arbitrarily many projects. As shown above, projects can be located anywhere in the installation. They don’t have to be subdirectories of the manifest directory, and they can be inside of arbitrary subdirectories inside the installation’s root directory. By default, the Zephyr build system uses west to get the locations of all the projects in the installation, so any code they contain can be used by applications. This behavior can be overridden using the ZEPHYR_MODULES CMake variable; see cmake/zephyr_module.cmake for details.

Finally, any repository managed by a west installation 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 three source code topologies supported by west:

  • T1: Star topology with zephyr as the manifest repository:

    • The zephyr repository acts as the central repository and includes a complete list of projects used upstream

    • Default (upstream) configuration

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

    • See Introduction for how mainline Zephyr is an example of this topology

  • T2: Star topology with an application repository as the manifest repository:

    • A repository containing a Zephyr application acts as the central repository and includes a complete list of other projects, including the zephyr repository, required to build it

    • Useful for those focused on a single application

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

    • An installation using this topology could look like this:

      ├── application
      │   ├── CMakeLists.txt
      │   ├── prj.conf
      │   ├── src
      │   │   └── main.c
      │   └── west.yml
      ├── modules
      │   └── lib
      │       └── tinycbor
      └── zephyr
  • T3: Forest topology:

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

    • Useful for downstream distributions with no “central” repository

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

    • An installation using this topology could look like this:

      ├── app1
      │   ├── CMakeLists.txt
      │   ├── prj.conf
      │   └── src
      │       └── main.c
      ├── app2
      │   ├── CMakeLists.txt
      │   ├── prj.conf
      │   └── src
      │       └── main.c
      ├── manifest-repo
      │   └── west.yml
      ├── modules
      │   └── lib
      │       └── tinycbor
      └── zephyr

West Structure

West’s code is distributed via PyPI in a namespace 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 PATH. This 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 installation 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 installation 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 installation 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 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 --freeze [-o outfile]: Save a “frozen” representation of the current manifest; all revision fields are converted to SHAs based on the current manifest-rev branches.

  • 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 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.