Custom Registry Mirrors

Dagger can be configured to use container registry mirrors for any registry URL. This allows container images that refer to one registry to instead be redirected to a different one.

Create a file named engine.toml that contains the registry mirror:

debug = true
insecure-entitlements = ["security.insecure"]

[registry."docker.io"]
  mirrors = ["mirror.gcr.io"]

This configuration can be repeated for multiple registries and mirrors if needed:

[registry."docker.io"]
  mirrors = ["mirror.a.com", "mirror.b.com"]

[registry."some.other.registry.com"]
  mirrors = ["mirror.foo.com", "mirror.bar.com"]

Manually start Dagger with the custom engine.toml:

docker run --rm -v /var/lib/dagger --name customized-dagger-engine --privileged --volume $PWD/engine.toml:/etc/dagger/engine.toml registry.dagger.io/engine:v0.10.2

Execute the following commands to test the configuration:

export _EXPERIMENTAL_DAGGER_RUNNER_HOST=docker-container://customized-dagger-engine
dagger query --progress=plain <<< '{ container { from(address:"hello-world") { stdout } } }'

The specified hello-world container will now be pulled from the mirror instead of from Docker Hub.