Container runtimes

When the Dagger CLI is run on the host, it needs to connect to an engine. The most common way to do this is to rely on a container runtime available on the host to start the engine in a container.

Dagger can be used with most OCI-compatible container runtimes, including:

• docker
• podman
• nerdctl / finch
• Apple's container

How it works

By default, dagger will attempt to detect an available container runtime on the host - no need for additional configuration.

If you need to override the default you can set _EXPERIMENTAL_DAGGER_RUNNER_HOST, using the connection interface.

When attempting to connect to the engine via the selected container runtime, the CLI will attempt to download the engine image that matches its own version, start it in a container, then connect to it for the request.

The selected container runtime also provides the backend for APIs in the dagger engine that rely on a host container runtime, such as:

• Host.containerImage(name: String!): Container! (loads an image into the engine)
• Container.exportImage(name: String!): Void! (exports a container image into the host)