Building docker image with Forgejo Actions

aka how I nearly went crazy trying to figure out how to build docker images in Forgejo Actions.

With the default setup from here you can get up and running with foregjo actions but it won’t allow you to build docker images inside your workflows.

When I tried to build a docker image in a workflow I kept getting the following:

ERROR: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
::error::buildx failed with: ERROR: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

It’s quite a common error and something that should be easy to fix but when you throw docker-in-docker in to the mix it becomes way more complex.

To cut a long story short I found a comment with a link to this example which was confirmed to be working, after a few tweaks I came up with the docker compose below. I’ve removed the need to be running forgejo already (I have set in a separate compose) and updated the base image.

# Copyright 2024 The Forgejo Authors.
# SPDX-License-Identifier: MIT

#
# Create a secret with:
#
#   openssl rand -hex 20
#
# Replace all occurences of {SHARED_SECRET} below with the output.
#
# NOTE: a token obtained from the Forgejo web interface cannot be used
#       as a shared secret.
#
# Replace {ROOT_PASSWORD} with a secure password
#

volumes:
  docker_certs:

services:

  docker-in-docker:
    image: code.forgejo.org/oci/docker:dind
    hostname: docker  # Must set hostname as TLS certificates are only valid for docker or localhost
    privileged: true
    environment:
      DOCKER_TLS_CERTDIR: /certs
      DOCKER_HOST: docker-in-docker
    volumes:
      - docker_certs:/certs

  runner-register:
    image: code.forgejo.org/forgejo/runner:6.2.2
    links:
      - docker-in-docker
    environment:
      DOCKER_HOST: tcp://docker-in-docker:2376
    volumes:
	  - ./data:/data
    user: 0:0
    command: >-
      bash -ec '
      while : ; do
        forgejo-runner create-runner-file --connect --instance https://code.remotelab.uk --name runner --secret {SHARED_SECRET} && break ;
        sleep 1 ;
      done ;
      sed -i -e "s|\"labels\": null|\"labels\": [\"docker-cli:docker://code.forgejo.org/oci/docker:cli\",\"node-bookworm:docker://code.forgejo.org/oci/node:20-bookworm\"]|" .runner ;
      forgejo-runner generate-config > config.yml ;
      sed -i -e "s|  level: info|  level: debug|" config.yml ;
      sed -i -e "s|network: .*|network: host|" config.yml ;
      sed -i -e "s|^  envs:$$|  envs:\n    DOCKER_HOST: tcp://docker:2376\n    DOCKER_TLS_VERIFY: 1\n    DOCKER_CERT_PATH: /certs/client|" config.yml ;
      sed -i -e "s|^  options:|  options: -v /certs/client:/certs/client|" config.yml ;
      sed -i -e "s|  valid_volumes: \[\]$$|  valid_volumes:\n    - /certs/client|" config.yml ;
      chown -R 1000:1000 /data
      '

  runner-daemon:
    image: code.forgejo.org/forgejo/runner:6.2.2
    links:
      - docker-in-docker
    environment:
      DOCKER_HOST: tcp://docker:2376
      DOCKER_CERT_PATH: /certs/client
      DOCKER_TLS_VERIFY: "1"
    volumes:
      - ./data:/data
      - docker_certs:/certs
    command: >-
      bash -c '
      while : ; do test -w .runner && forgejo-runner --config config.yml daemon ; sleep 1 ; done
      '

Hopefully this helps anyone else who comes across this issue.