Introduction

This guide is intended to help you create your own Docker image with Earthly inside it for your containerized CI workflows.

Getting Started

There are two ways to build a containerized CI image with Earthly:

• Extending the earthly/earthly image with an external runner/agent

• Adding Earthly to an existing image

This guide will cover both approaches to constructing your image.

Extending The earthly/earthly Image

This is the recommended approach when adopting Earthly into your containerized CI. Start by basing your custom image on ours:

FROM earthly/earthly:v0.5.23
RUN ... # Add your agent, certificates, tools...

When extending our image, be sure to pin to a specific version to avoid accidental future breakage as earthly evolves.

The earthly/earthly image is Alpine Linux based. To add tools to the image, you can use apk:

apk add --no-cache my-cool-tool

If you are adding a tool from outside the Alpine Linux repositories, test it to ensure it is compatible. Alpine uses musl, which can create incompatibilities with some software.

Also, you should embed any configuration that your Earthly image might need (to avoid having it in your build scripts, or mounted from a host somewhere). You can do this in-line with the earthly config command.

Adding Earthly To An Existing Image

This section will cover adding Earthly to an existing image when:

• Docker-In-Docker is configured for the base image

• Earthly will be connecting to a remote earthly/buildkitd instance

While it is possible to configure a locally-ran earthly/buildkitd instance within an image (it's how earthly/earthly works), the steps and tweaks are beyond the scope of this guide.

Docker-In-Docker

In this setup, Earthly will be allowed to manage an instance of its earthly/buildkitd daemon over a live Docker socket.

To enable this, simply follow the installation instructions within your Dockerfile/Earthfile as you would on any other host. An example of installing this can be found below.

RUN wget https://github.com/earthly/earthly/releases/download/v0.5.23/earthly-linux-amd64 -O /usr/local/bin/earthly && \
    chmod +x /usr/local/bin/earthly && \
    /usr/local/bin/earthly bootstrap

As with the Docker containers, be sure to pin the version in the download URL to avoid any accidental future breakage. Assuming Docker is also installed and available, you should be able to invoke Earthly without any additional configuration.

Remote Daemon

When connecting to a remote daemon, follow the Docker-In-Docker installation instructions above to get the binary. Then you'll need to issue a few earthly config commands to ensure the container is set up to automatically use the remote daemon. It might look something like this:

RUN earthly config global.buildkit_host buildkit_host: 'tcp://myhost:8372'

For more details on using a remote buildkit daemon, see our guide.