buildx/docs/guides/cache/local.md

Local cache storage

The local cache store is a simple cache option that stores your cache as files in a directory on your filesystem, using an OCI image layout for the underlying directory structure. Local cache is a good choice if you're just testing, or if you want the flexibility to self-manage a shared storage solution.

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=local,dest=path/to/local/dir[,parameters...] \
  --cache-from type=local,src=path/to/local/dir .

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

Name	Option	Type	Default	Description
src	cache-from	String		Path of the local directory where cache gets imported from.
digest	cache-from	String		Digest of manifest to import, see cache versioning.
dest	cache-to	String		Path of the local directory where cache gets exported to.
mode	cache-to	min,max	min	Cache layers to export, see cache mode.
oci-mediatypes	cache-to	true,false	true	Use OCI media types in exported manifests, see OCI media types.
compression	cache-to	gzip,estargz,zstd	gzip	Compression type, see cache compression.
compression-level	cache-to	0..22		Compression level, see cache compression.
force-compression	cache-to	true,false	false	Forcibly apply compression, see cache compression.

If the src cache doesn't exist, then the cache import step will fail, but the build will continue.

Cache versioning

This section describes how versioning works for caches on a local filesystem, and how you can use the digest parameter to use older versions of cache.

If you inspect the cache directory manually, you can see the resulting OCI image layout:

$ ls cache
blobs  index.json  ingest
$ cat cache/index.json | jq
{
  "schemaVersion": 2,
  "manifests": [
    {
      "mediaType": "application/vnd.oci.image.index.v1+json",
      "digest": "sha256:6982c70595cb91769f61cd1e064cf5f41d5357387bab6b18c0164c5f98c1f707",
      "size": 1560,
      "annotations": {
        "org.opencontainers.image.ref.name": "latest"
      }
    }
  ]
}

Like other cache types, local cache gets replaced on export, by replacing the contents of the index.json file. However, previous caches will still be available in the blobs directory. These old caches are addressable by digest, and kept indefinitely. Therefore, the size of the local cache will continue to grow (see moby/buildkit#1896 for more information).

When importing cache using --cache-to, you can specify the digest parameter to force loading an older version of the cache, for example:

$ docker buildx build --push -t <registry>/<image> \
  --cache-to type=local,dest=path/to/local/dir \
  --cache-from type=local,ref=path/to/local/dir,digest=sha256:6982c70595cb91769f61cd1e064cf5f41d5357387bab6b18c0164c5f98c1f707 .

Further reading

For an introduction to caching see Optimizing builds with cache.

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