Registry cache

The registry cache storage can be thought of as an extension to the inline cache. Unlike the inline cache, the registry cache is entirely separate from the image, which allows for more flexible usage - registry-backed cache can do everything that the inline cache can do, and more:

  • Allows for separating the cache and resulting image artifacts so that you can distribute your final image without the cache inside.
  • It can efficiently cache multi-stage builds in max mode, instead of only the final stage.
  • It works with other exporters for more flexibility, instead of only the image exporter.

This cache storage backend is not supported with the default docker driver. To use this feature, create a new builder using a different driver. See Build drivers for more information.

Synopsis

Unlike the simpler inline cache, the registry cache supports several configuration parameters:

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

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

NameOptionTypeDefaultDescription
refcache-to,cache-fromStringFull name of the cache image to import.
destcache-toStringPath of the local directory where cache gets exported to.
modecache-tomin,maxminCache layers to export, see cache mode.
oci-mediatypescache-totrue,falsetrueUse OCI media types in exported manifests, see OCI media types.
compressioncache-togzip,estargz,zstdgzipCompression type, see cache compression.
compression-levelcache-to0..22Compression level, see cache compression.
force-compressioncache-totrue,falsefalseForcibly apply compression, see cache compression.
ignore-errorcache-toBooleanfalseIgnore errors caused by failed cache exports.

You can choose any valid value for ref, as long as it's not the same as the target location that you push your image to. You might choose different tags (e.g. foo/bar:latest and foo/bar:build-cache), separate image names (e.g. foo/bar and foo/bar-cache), or even different repositories (e.g. docker.io/foo/bar and ghcr.io/foo/bar). It's up to you to decide the strategy that you want to use for separating your image from your cache images.

If the --cache-from target doesn't exist, then the cache import step will fail, but the build continues.

Further reading

For an introduction to caching see Optimizing builds with cache.

For more information on the registry cache backend, see the BuildKit READMEopen_in_new.