buildx/docs/guides/cache/gha.md

GitHub Actions cache storage

Warning

The GitHub Actions cache is a beta feature. You can use it today, in current releases of Buildx and BuildKit. However, the interface and behavior are unstable and may change in future releases.

The GitHub Actions cache utilizes the GitHub-provided Action's cache available from within your CI execution environment. This is the recommended cache to use inside your GitHub action pipelines, as long as your use case falls within the size and usage limits set by GitHub.

Note

This cache storage backend requires using a different driver than the default docker driver - see more information on selecting a driver here. To create a new driver (which can act as a simple drop-in replacement):

$ docker buildx create --use --driver=docker-container

Synopsis

$ docker buildx build --push -t <registry>/<image> \
  --cache-to type=gha[,parameters...] \
  --cache-from type=gha[,parameters...] .

The following table describes the available CSV parameters that you can pass to --cache-to and --cache-from.

Name	Option	Type	Default	Description
url	cache-to,cache-from	String	$ACTIONS_CACHE_URL	Cache server URL, see authentication.
token	cache-to,cache-from	String	$ACTIONS_RUNTIME_TOKEN	Access token, see authentication.
scope	cache-to,cache-from	String	Name of the current Git branch.	Cache scope, see scope
mode	cache-to	min,max	min	Cache layers to export, see cache mode.

Authentication

If the url or token parameters are left unspecified, the gha cache backend will fall back to using environment variables. If you invoke the docker buildx command manually from an inline step, then the variables must be manually exposed (using crazy-max/ghaction-github-runtime, for example).

Scope

By default, cache is scoped per Git branch. This ensures a separate cache environment for the main branch and each feature branch. If you build multiple images on the same branch, each build will overwrite the cache of the previous, leaving only the final cache.

To preserve the cache for multiple builds on the same branch, you can manually specify a cache scope name using the scope parameter. In the following example, the cache is set to a combination of the branch name and the image name, to ensure each branch gets its own cache):

$ docker buildx build --push -t <registry>/<image> \
  --cache-to type=gha,url=...,token=...,scope=$GITHUB_REF_NAME-image \
  --cache-from type=gha,url=...,token=...,scope=$GITHUB_REF_NAME-image .
$ docker buildx build --push -t <registry>/<image2> \
  --cache-to type=gha,url=...,token=...,scope=$GITHUB_REF_NAME-image2 \
  --cache-from type=gha,url=...,token=...,scope=$GITHUB_REF_NAME-image2 .

GitHub's cache access restrictions, still apply. Only the cache for the current branch, the base branch and the default branch is accessible by a workflow.

Using docker/build-push-action

When using the docker/build-push-action, the url and token parameters are automatically populated. No need to manually specify them, or include any additional workarounds.

For example:

- name: Build and push
  uses: docker/build-push-action@v3
  with:
    context: .
    push: true
    tags: "<registry>/<image>:latest"
    cache-from: type=gha
    cache-to: type=gha,mode=max

Further reading

For an introduction to caching see Optimizing builds with cache.

For more information on the gha cache backend, see the BuildKit README.