Docker Build Cloud with Kamal

Awhile ago I ran into an issue with TailwindCSS v4 not building a docker container (details here), which lead to discovering Kamal’s remote builders.

Well last week, while deploying to a side project (which was using a remote builder on the same machine) it kept dying while building the image. I could have figured out why it was happening, but this seemed like a good opportunity to look into DockerHub’s Build Cloud service.

Turns out all you need to do is create a new cloud builder in Build Cloud’s web dashboard and update the builder in your Kamal deploy.yml to include a new driver:

builder:
  arch: amd64
  driver: cloud organization_name/builder_name

That’s it. Once that change was in place my first build took about 2 minutes, and with caching all subsequent builds have been about 45 seconds each.