How to configure gitlab-runner to run in the same docker host as gitlab?

Question

I have a gitlab instance running in a docker container. Now I would like to setup gitlab-runner on the same host. Both are running:

docker container ls
CONTAINER ID        IMAGE                         COMMAND                  CREATED              STATUS                 PORTS                                                            NAMES
279473dceb2f        gitlab/gitlab-runner:alpine   "/usr/bin/dumb-ini..."   About a minute ago   Up About a minute                                                                       gitlab-runner
6d7af0d6b946        gitlab/gitlab-ce:latest       "/assets/wrapper"        2 hours ago          Up 2 hours (healthy)   0.0.0.0:80->80/tcp, 0.0.0.0:443->443/tcp, 0.0.0.0:8022->22/tcp   gitlab

I registered a docker image as a shared runner:

concurrent = 1
check_interval = 0

[[runners]]
  name = "default shared maven runner"
  url = "http://url-of-my-gitlab.instance"
  token = "valid token"
  executor = "docker"
  [runners.docker]
    pull_policy = "never"
    tls_verify = false
    image = "maven-java-8:latest"
    privileged = false
    disable_cache = false
    volumes = ["/cache"]
    shm_size = 0
  [runners.cache]

The registered image maven-java-8 is a custom image with the correct settings.xml and it is listed in docker images.

But still the pipeline fails with:

Running with gitlab-ci-multi-runner 9.3.0 (3df822b)
  on Maven Test (5b2573e4)
Using Docker executor with image maven-java-8 ...
Using docker image  sha256:c266311d78b33f89f6eecce00f19a0428e37ba6af6734c8fced32fa11e4bd4ba for predefined container...
Pulling docker image maven-java-8 ...
ERROR: Job failed: Error response from daemon: repository maven-java-8 not found: does not exist or no pull access

Which I interpret as it is trying to use the local images inside of the gitlab-runner container.

The GitLab version is gitlab-ce 9.2.7 and the runner version is v9.3.0.

The content of my .gitlab-cy.yml is:

test:
  script:
    - mvn clean test

What am I missing?

Answer 1

Management Summary

Set the pull_policy to "never" in the [runners.docker] section by calling:

docker exec -it gitlab-runner \
  vi /etc/gitlab-runner/config.toml

Detailed Description

It seemed the problem was a confusion with images and mounted volumes.

The documentation says to configure runners in:

/etc/gitlab-runner/config.toml

Which I did, but on the host machine. When running gitlab-runner in a docker container, it mounts a volume:

... -v /srv/gitlab-runner/config:/etc/gitlab-runner ...

This means, that the configuration file in /etc/... in the container is mounted to /srv/... on the host machine.

In this file the pull_policy was not set, which defaults to always, what ultimately caused my problem in the first place.