I am using a custom docker image to run a github workflow, whose ultimate purpose is to build and push an image to a GCR. I am using a custom image because the build process needs a lot of prerequisites installed. I want to speed up the CI workflow and I want the Dockerfile to act as a manifest for what the build environment needs.

The issue is connecting to docker.sock. I get a permission denied error. Here is the minimal Dockerfile:

FROM ubuntu:latest

RUN apt-get update && 
    apt-get install -y 
        curl 
    && apt-get clean 
    && rm -rf /var/lib/apt/lists/*

RUN curl -fsSL https://get.docker.com -o get-docker.sh
RUN sh get-docker.sh

Here is the minimal workflow file:

name: Deploy to staging

on:
  push:
    tags:
      - '*'
jobs:
  deploy:
    runs-on: ubuntu-latest
    container: 
      image: eu.gcr.io/my-image
      credentials:
        username: _json_key
        password: ${{ secrets.TOKEN }}
    env:
      ...
    steps:
      - name: call docker
        run: docker images

I can reproduce the issue locally by running the container and doing docker images (or any docker command) it can’t connect to the docker daemon:

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

I can solve this locally by mounting the host docker.sock with:

docker run -it -v /var/run/docker.sock:/var/run/docker.sock

But I can’t mount docker.sock do that on a github runner (I assume for security reasons). The issue is not adding the user to the docker group. I tried that. I believe the issue is inherent in trying to run docker commands on a custom image in a github workflow.

How can I solve this problem? Is there a way in github actions, or is another CI tool more suitable?