[Earthly +v0.8.10 feature]: Disabling Earthly internal labels

NOTE: This has not been yet updated in the Earthly documentation, but I’m pretty sure it will be soon (and I’ll update this post accordingly)

What does labels do to reproducible builds?

By default, Earthly adds dev.earthly.* labels in the built image. You can find these by doing a docker inspect <imageID> | jq -r '.[].Config.Labels'.

Here’s an example of the image configuration including the dev.earthly.* labels:

    "Config": {
        ...
        "Labels": {
            "dev.earthly.built-by": "homebrew",
            "dev.earthly.git-sha": "6b41f8409d7ffef0d25072c2c04250074b6e3c72",
            "dev.earthly.version": "v0.8.14",
            ...
        }
    }

You may probably infer what’s the potential issue with these values.

If any of your execution environment, git-sha, or Earthly version changes, the final image checksum changes. Even if the image contents are identically the same.

There are image registry implementations that can handle duplicated checksums with a different mechanism, like avoiding to push duplicated images.

Even tho these labels are important in terms of information, certain use-cases require including this information (or not) in its own label domain. Labels impact on the build reproducibility, cause it changes the produced hashes of the images, leading to potentially duplicated images.

By stripping out the labels, we can have full control through our custom domain labels, and avoid duplicated artifacts to be pushed upstream.

That’s why the flag –allow-without-earthly-labels was proposed by the Earthly Team and implemented by myself.

You can read more information in the issue.

How this feature works?

From Earthly v0.8.10, the --allow-without-earthly-labels feature flag has been added.

The way to use is as follows:

    VERSION --allow-without-earthly-labels 0.8
    # Enable with the VERSION `--allow-without-earthly-labels` feature flag.
    ...
    SAVE IMAGE --push --without-earthly-labels ....
    # Add the --without-earthly-labels flag to the SAVE IMAGE command.

Thanks for reading!