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Repository: govuk-ruby-images

Base container images for GOV.UK Ruby apps



What’s in this repo

This repo contains Docker images intented for use as a base for GOV.UK app containers. The govuk-ruby-base image contains a Ruby installation, along with node.js and yarn. The govuk-ruby-builder image contains environment variables and configuration for building Ruby applications.


Use the two images in your app’s Dockerfile:

FROM AS builder

# your build steps here


# your app image steps here

Common problems and resolutions

ERROR: failed to solve: cannot copy to non-directory: /var/lib/docker/overlay2/.../merged/app/tmp

Add tmp/ to your .dockerignore. This is necessary because we symlink $APP_HOME/tmp to /tmp as a workaround for some badly-behaved gems that assume they can write to Path.join(Rails.root, 'tmp') so that we can run with readOnlyRootFilesystem.

Managing Ruby versions

Ruby version information is kept in the versions directory. Each file in this directory is a shell script containing three variables that define a Ruby version:

  • RUBY_MAJOR: The major and minor Ruby version, excluding the patch version. For example, 3.2. The image will be tagged with this version number (with . instead of _) unless RUBY_IS_PATCH is equal to the string true.
  • RUBY_VERSION: The full Ruby version, including patch version. This is used to download the Ruby source distribution. The image will be tagged with this version number, regardless of the value of RUBY_IS_PATCH.
  • RUBY_IS_PATCH: If equal to the string true then this version will not be tagged with the major.minor version number. (It will be tagged only with the full version number that includes the patch version.)

Hashes of source tarballs for verification

The file SHA256SUMS contains the SHA-256 hashes of the Ruby and OpenSSL source tarballs. These are verified at build-time.

To add hashes for new Ruby/OpenSSL versions:

  1. Download the new source tarball(s).

  2. Run sha256sum *gz >>SHA256SUMS. If your system doesn’t have sha256sum, try shasum -a256.

  3. Compare the new hashes with those listed on the Ruby downloads page and OpenSSL downloads page.


GOV.UK Platform Engineering team looks after this repo. If you’re inside GDS, you can find us in #govuk-platform-engineering or view our kanban board.