This is an experiment to build ChromeOS with Bazel.
For the prototyping phase, we're working on building a snapshot of ChromiumOS. Use
repo to check out a snapshotted ChromiumOS tree + Bazel files.
$ mkdir ~/chromiumos $ cd ~/chromiumos $ repo init -u https://chrome-internal.googlesource.com/chromeos/manifest-internal -b stabilize-15429.B $ repo sync -c -j 4 $ cd src
We're still in the process of moving our development from the Google-internal experimental repository to the public ChromiumOS repository. Meanwhile you need the following hack to make the build pass.
$ ln -s platform/rules_cros rules_cros
Unless otherwise specified, examples in this doc assume that your current directory is
You need to use a certain version of Bazel to build ChromeOS. The easiest way is to install and use Bazelisk that automatically downloads an appropriate version of Bazel:
GOBIN=$HOME/go/bin go install github.com/bazelbuild/bazelisk@latest
You‘ll also need to get Bazelisk onto your PATH, to be executed before any Bazel that’s already on your PATH, and we‘d like to invoke Bazelisk whenever we run
bazel. Create a symlink to bazelisk in a directory that’ll be on your PATH before any other bazels, and name the link
ln -s ~/go/bin/bazelisk ~/bin/bazel
To build sys-apps/attr:
$ BOARD=arm64-generic bazel build @portage//sys-apps/attr
To build all target packages:
$ BOARD=arm64-generic bazel build --keep_going //:all_target_packages
This is a short-cut to build
We have the following targets to build images:
//images:chromiumos_minimal_image: Minimal image that contains
//images:chromiumos_base_image: Base image.
//images:chromiumos_dev_image: Dev image.
//images:chromiumos_test_image: Test image.
As of 2023-04-25, we primarily test our builds for amd64-generic. We also have known build issues in some packages:
chromeos-base/chromeos-chrome: Takes too long time (multiple hours) to build. Also randomly fails to build (b/273830995).
You can inject prebuilt binary packages to bypass building those packages to build a base image. You can pass
--config=prebuilts/amd64-generic to do this easily for amd64-generic.
$ BOARD=amd64-generic bazel build --config=prebuilts/amd64-generic //images:chromiumos_base_image
See Injecting prebuilt binary packages for more details.
After building an image, you can use
cros_vm command available in CrOS SDK to run a VM locally. Make sure to copy an image out from
bazel-bin as it's not writable by default.
$ cp bazel-bin/images/chromiumos_base_image.bin /tmp/ $ chmod +w /tmp/chromiumos_base_image.bin $ chromite/bin/cros_vm --start --board=amd64-generic --image-path /tmp/chromiumos_base_image.bin
You can use VNC viewer to view the VM.
$ vncviewer localhost:5900
You can also use
cros_vm command to stop the VM.
$ chromite/bin/cros_vm --stop
cmd ... misc commands for development
private/ ... contains programs used by Bazel rules
alchemist ... generates a Bazel repository on
cmd/ commands internally used in the build
action_wrapper/ ... the generic wrapper of Bazel actions, handling logs and signals
build_image/ ... builds ChromeOS images
build_package/ ... builds a Portage binary package; used by
build_sdk/ ... builds SDK squashfs; used by
extract_interface/ ... builds an interface library
fakefs/ ... simulates chown(2) in unprivileged user namespaces
install_deps/ ... installs binary packages into an ephemeral SDK
run_in_container/ ... runs a program within an unprivileged Linux container; used by other programs such as
sdk_from_archive/ ... creates a base ephemeral SDK from an archive
sdk_update/ ... updates an ephemeral SDK with patches and packages
common/ ... common Rust/Go libraries
prebuilts/ ... defines prebuilt binaries
images/ ... defines ChromeOS image targets
sdk/ ... defines the base SDK
tools/ ... misc small tools for development
workspace_root/ ... contains various files to be symlinked to the workspace root, including
If a package is failing to build, it‘s sometimes useful to view the package’s work directory. To do this run:
bazel build --sandbox_debug //your/ebuild
In the build output you will see a
cd into the
This directory will contain a directory called
build_package.*. It contains all the artifacts that were generated while building the package.
Build logs can be found in:
The package work dir can be found in:
Sometimes you want to enter an ephemeral CrOS chroot where a package build is failing to inspect the environment interactively.
To enter an ephemeral CrOS chroot, run the following command:
$ BOARD=arm64-generic bazel run @portage//sys-apps/attr:debug -- --login=after
This command will give you an interactive shell after building a package. You can also specify other values to
--login to choose the timing to enter an interactive console:
--login=before: before building the package
--login=after: after building the package
--login=after-fail: after failing to build the package
In the case your work is blocked by some package build failures, you can workaround them by injecting prebuilt binary packages via command line flags.
ebuild target under
@portage//internal/packages/..., an associated string flag target is defined. You can set a
gs:// URL of a prebuilt binary package to inject it.
For example, to inject a prebuilt binary packages for
chromeos-chrome, you can set this option:
We have several named config groupings in prebuilts.bazelrc that define typical options to inject prebuilts. You can specify
--config to use them.
--config=prebuilts/amd64-generic: Injects prebuilt binary packages needed to build amd64-generic images.
In case you need to extract the contents of a binary package so you can easily inspect it, you can use the
xpak split CLI.
bazel run //bazel/ebuild/cmd/xpak:xpak -- split --extract libffi-3.1-r8.tbz2 libusb-0-r2.tbz2
If you'd like to run the tests every time you commit, add the following. You can skip it with
git commit --no-verify.
cd ~/chromiumos/src/bazel ln -s tools/run_tests.sh .git/hooks/pre-commit