Use the Earthly CI Image

Introduction

This guide is intended to help you use the Earthly image for your containerized CI workflows.

Prerequisites

The earthly/earthly image requires that it is run as --privileged, or alternatively, it is run without the embedded Buildkit daemon (NO_BUILDKIT=1).

Getting Started

Please see the reference documentation of the earthly/earthly image on DockerHub.

It is recommended that the earthly/earthly image is used with a pinned version when used in the context of a CI, in order to avoid accidental future breakage as earthly evolves.

Using /usr/bin/earthly-entrypoint.sh as the entrypoint

The earthly/earthly image comes with an entrypoint that first starts up BuildKit and then issues an earthly command that makes use of it. You may use the image just as you would use earthly itself otherwise. Any arguments are passed into the earthly command directly.

Important

Note that using the earthly binary as the entrypoint will not start up BuildKit within the same container and will instead attempt to use the Docker Daemon (assuming one is available via /var/run/docker.sock) to start up BuildKit.

Remote Daemon

An alternative option is to use the earthly/earthly image in conjunction with a remote BuildKit Daemon. You may use the environment variable BUILDKIT_HOST to specify the hostname of the remote BuildKit Daemon. When this environment variable is set, the earthly/earthly image will not attempt to start BuildKit and will instead use the remote BuildKit Daemon.

You may also use the earthly/earthly image to run a build against an Earthly Satellite. To achieve this you can pass along an EARTHLY_TOKEN environment variable, along with the command-line flags --sat and --org, to point the build to a specific satellite.

For more details on using remote execution, see our guide on remote Buildkit or the introduction to Satellites.

Mounting the source code

The image expects the source code of the application you are building in the current working directory (by default /workspace). You will need to copy or mount the necessary files to that directory prior to invoking the entrypoint.

docker run --privileged --rm -v "$PWD":/workspace earthly/earthly:v0.8.9 +my-target

Or, if you would like to use an alternative directory:

docker run --privileged --rm -v "$PWD":/my-dir -w /my-dir earthly/earthly:v0.8.9 +my-target

Alternatively, you may rely on Earthly to perform a git clone, by using the remote target reference format. For example:

docker run --privileged --rm earthly/earthly:v0.8.9 github.com/foo/bar:my-branch+target

NO_BUILDKIT Environment Variable

As the embedded Buildkit daemon requires --privileged, for some operations you may be able to use the NO_BUILDKIT=1 environment variable to disable the embedded Buildkit daemon. This is especially useful when running against a remote buildkit (like a Satellite), or when not performing a build as part of the command (like when using earthly account).

An important note about running the image

When running the built image in your CI of choice, if you're not using a remote daemon, Earthly will start Buildkit within the same container. In this case, it is important to ensure that the directory used by Buildkit to cache the builds is mounted as a Docker volume. Failing to do so may result in excessive disk usage, slow builds, or Earthly not functioning properly.

Important

We strongly recommend using a Docker volume for mounting /tmp/earthly. If you do not, Buildkit can consume excessive disk space, operate very slowly, or it might not function correctly.

In some environments, not mounting /tmp/earthly as a Docker volume results in the following error:

--> WITH DOCKER RUN --privileged ...
...
rm: can't remove '/var/earthly/dind/...': Resource busy

For more information, see the documentation for earthly/earthly on DockerHub.