Configure a Custom Registry Mirror

The Dagger Engine 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 the Dagger Engine with the custom engine.toml:

docker run --rm --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 } } }'

You should see the specified hello-world container being pulled from the mirror instead of from Docker Hub.