Remote BuildKit

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Remote BuildKit
Note
Using a remote BuildKit instance is currently experimental. If you run into any issues, or need help, don't hesitate to reach out!
Introduction
In some cases, you may want to run a remote instance of earthly/buildkitd. This guide is intended to help you identify if you might benefit from this configuration, and to help you set it up correctly.
Why Remote?
Running a remote daemon is a unique feature of Earthly. It allows the build to happen elsewhere; even when executing it from your local development machine. However, it is not always the best option. Before setting up a remote daemon, first look into Earthly's shared caching capabilities and see if those can get you the boost you need. In our experience, shared caching is usually enough.
However, there are instances where a remote daemon can make the most sense. Here are some examples:
You have a single, powerful build machine you would like to share with your development team
There is data closer to a remote machine than your development/CI environment, so you bring the build to the data
You are using Earthly in Kubernetes, and want to isolate the containers doing the actual building because they require privileged mode
You want to share a build machine (or cluster) with your CI environment and your developers
Your local computer does not have the capabilities to build the software (docker/dockerd is missing, or you lack sufficient privileges, or it is simply not powerful enough)
Running Remote BuildKit
To run a remote BuildKit instance, deploy and configure the image earthly/buildkitd.
Networking
A remote daemon should be reachable by all clients intending to use it. Earthly uses ports 8371-8373 to communicate, so these should be open and available.
Mounts
/tmp/earthly
This path within the container is the location that Buildkit uses for storing the cache. Because this folder sees a lot of traffic, its important that it remains fast.
Important
We strongly recommend using a Docker volume for mounting /tmp/earthly. If you do not, buildkitd 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
In EKS, users reported that mounting an EBS volume, instead of a Kubernetes emptyDir worked.
This part of our documentation needs improvement. If you have a Kubernetes-based setup, please let us know how you have mounted EARTHLY_TMP_DIR and whether WITH DOCKER worked well for you.
Daemon
To configure an earthly/buildkitd daemon as a remotely available daemon, you will need to start the container yourself. See our configuration docs for more details on all the options available; but here are the ones you need to know:
BUILDKIT_TCP_TRANSPORT_ENABLED
This will configure buildkitd to listen on port 8372. If you would like it to be externally available on a different port, you will need to handle that at the port mapping level. TCP is required for remotely sharing a daemon.
BUILDKIT_TLS_ENABLED
Set this to true for all daemons that will handle production workloads. This daemon by design is an arbitrary code execution machine, and running it without any kind of mTLS configuration is not recommended.
Make sure you mount your certificates and keys in the correct location (/etc/*.pem).
For complete details, see the documentation for earthly/buildkitd on DockerHub.
Client
Normally, Earthly will try to start and manage its own earthly/buildkitd daemon. However, when relying on a remote earthly/buildkitd instance, Earthly will not attempt to manage this daemon. Here are the configuration options needed to use a remote instance:
buildkit_host
This is the address of the remote daemon. It should look something like this: tcp://my-cool-remote-daemon:8372. If the hostname is considered to be a "local" one, Earthly will fall back to the Local-Remote behaviors described below. For reference; all IPv6 Loopback addresses, 127.0.0.1, and [localhost](http://localhost) are considered to be "local". The machine's hostname is not considered "local".
tlsca / tlscert / tlskey
These are the paths to the certificates and keys used by the client when communicating with an mTLS-enabled daemon. These paths are relative to the Earthly config (usually ~/.earthly/config.yaml, unless absolute paths are specified.
tls_enabled
Set this to true when using TLS is desired.
Local-Remote
It is also possible to use the remote protocols (TCP and mTLS) locally, while still letting Earthly manage the daemon container. You can do this by enabling mTLS(tls_enabled).
By doing this, Earthly will (optionally) generate its own certificates, and connect to the daemon using tcp://127.0.0.1:8372. This is a great way to test some of the remote capabilities without having to generate certificates or manage a separate machine.
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Outline
Introduction
Why Remote?
Running Remote BuildKit
Local-Remote