Run GitLab Runner in a container

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This page explains how to run GitLab Runner inside a Docker container.

GitLab Runner Docker images are based on Ubuntu or Alpine Linux. They are wrappers around the standard gitlab-runner command, like if you installed GitLab Runner directly on the host.

This setup delegates full control over the Docker daemon to each GitLab Runner container. The effect is that isolation guarantees break if you run GitLab Runner inside a Docker daemon that also runs other payloads.

In this setup, every GitLab Runner command you run has a docker run equivalent, like this:

  • Runner command: gitlab-runner <runner command and options...>
  • Docker command: docker run <chosen docker options...> gitlab/gitlab-runner <runner command and options...>

For example, to get the top-level help information for GitLab Runner, replace the gitlab-runner part of the command with docker run [docker options] gitlab/gitlab-runner, like this: 

docker run --rm -t -i gitlab/gitlab-runner --help

NAME:
   gitlab-runner - a GitLab Runner

USAGE:
   gitlab-runner [global options] command [command options] [arguments...]

VERSION:
   16.5.0 (853330f9)

(...)

The rest of the command stays as described in the register documentation. The only difference is that the gitlab-runner command runs in a Docker container.

Docker Engine version compatibility

The versions for the Docker Engine and GitLab Runner container image do not have to match. The GitLab Runner images are backwards and forwards compatible. To ensure you have the latest features and security updates, you should always use the latest stable Docker Engine version.

Install the Docker image and start the container

Prerequisites:

  • You have installed Docker.
  • You have read the FAQ to learn about common problems in GitLab Runner.

  1. When you run gitlab-runner in a Docker container, ensure the configuration is not lost when you restart the container. Mount a permanent volume on which the configuration will reside, in either:

  2. Optional. If using a session_server, expose port 8093 by adding -p 8093:8093 to your docker run commands.

  3. Optional. To use the Docker Machine executor for autoscaling, mount the Docker Machine storage path (/root/.docker/machine) by adding a volume mount to your docker run commands:

    • For system volume mounts, add -v /srv/gitlab-runner/docker-machine-config:/root/.docker/machine
    • For Docker named volumes, add -v docker-machine-config:/root/.docker/machine
  4. Register a new runner. The GitLab Runner container must be registered to pick up jobs.

Some available configuration options include:

From a local system volume

To use your local system for the configuration volume and other resources mounted into the gitlab-runner container:

  1. Optional. In MacOS systems, /srv does not exist by default. Create /private/srv, or another private directory, for setup.

  2. Run this command, modifying it as needed: 

    docker run -d --name gitlab-runner --restart always \
  -v /srv/gitlab-runner/config:/etc/gitlab-runner \
  -v /var/run/docker.sock:/var/run/docker.sock \
  gitlab/gitlab-runner:latest

From a Docker volume

To use a configuration container to mount your custom data volume:

  1. Create the Docker volume: 

    docker volume create gitlab-runner-config

  2. Start the GitLab Runner container using the volume you just created: 

    docker run -d --name gitlab-runner --restart always \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -v gitlab-runner-config:/etc/gitlab-runner \
  gitlab/gitlab-runner:latest

Update runner configuration

After you change the runner configuration in config.toml, apply your changes by restarting the container with docker stop and docker run.

Upgrade runner version

Prerequisites:

  • You must use the same method for mounting your data volume as you did originally (-v /srv/gitlab-runner/config:/etc/gitlab-runner or -v gitlab-runner-config:/etc/gitlab-runner).

  1. Pull the latest version (or a specific tag): 

    docker pull gitlab/gitlab-runner:latest

  2. Stop and remove the existing container: 

    docker stop gitlab-runner && docker rm gitlab-runner

  3. Start the container as you did originally: 

    docker run -d --name gitlab-runner --restart always \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -v /srv/gitlab-runner/config:/etc/gitlab-runner \
  gitlab/gitlab-runner:latest

View runner logs

Log file locations depend on how you start a runner. When you start it as a:

  • Foreground task, either as a locally installed binary or in a Docker container, the logs print to stdout.
  • System service, like with systemd, the logs are available in the system logging mechanism, like Syslog.
  • Docker-based service, use the docker logs command, as the gitlab-runner ... command is the main process of the container.

For example, if you start a container with this command, its name is set to gitlab-runner: 

docker run -d --name gitlab-runner --restart always \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -v /srv/gitlab-runner/config:/etc/gitlab-runner \
  gitlab/gitlab-runner:latest

To view its logs, run this command, replacing gitlab-runner with your container name: 

docker logs gitlab-runner

For more information about handling container logs, see docker container logs in the Docker documentation.

Install trusted SSL server certificates

If your GitLab CI/CD server uses self-signed SSL certificates, make sure your runner container trusts the GitLab CI server certificate. This prevents communication failures.

Prerequisites:

  • Your ca.crt file should contain the root certificates of all the servers you want GitLab Runner to trust.
  1. Optional. The gitlab/gitlab-runner image looks for trusted SSL certificates in /etc/gitlab-runner/certs/ca.crt. To change this behavior, use the -e "CA_CERTIFICATES_PATH=/DIR/CERT" configuration option.
  2. Copy your ca.crt file into the certs directory on the data volume (or container).
  3. Optional. If your container is already running, restart it to import the ca.crt file on startup.

Docker images

In GitLab Runner 16.1, the Docker image based on Alpine uses Alpine 3.18. These multi-platform Docker images are available:

  • gitlab/gitlab-runner:latest based on Ubuntu, approximately 800 MB.
  • gitlab/gitlab-runner:alpine based on Alpine, approximately 460 MB.

See the GitLab Runner source for possible build instructions for both Ubuntu and Alpine images.

Create a runner Docker image

You can upgrade your image’s operating system before the update is available in the GitLab repositories.

Prerequisites:

  • You are not using the IBM Z image, as it does not contain the docker-machine dependency. This image is not maintained for the Linux s390x or Linux ppc64le platforms. For the current status, see issue 26551.

To build a gitlab-runner Docker image for the latest Alpine version:

  1. Create alpine-upgrade/Dockerfile. 

    ARG GITLAB_RUNNER_IMAGE_TYPE
ARG GITLAB_RUNNER_IMAGE_TAG
FROM gitlab/${GITLAB_RUNNER_IMAGE_TYPE}:${GITLAB_RUNNER_IMAGE_TAG}

RUN apk update
RUN apk upgrade

  2. Create an upgraded gitlab-runner image. 

    GITLAB_RUNNER_IMAGE_TYPE=gitlab-runner \
GITLAB_RUNNER_IMAGE_TAG=alpine-v17.5.0 \
docker build -t $GITLAB_RUNNER_IMAGE_TYPE:$GITLAB_RUNNER_IMAGE_TAG \
  --build-arg GITLAB_RUNNER_IMAGE_TYPE=$GITLAB_RUNNER_IMAGE_TYPE \
  --build-arg GITLAB_RUNNER_IMAGE_TAG=$GITLAB_RUNNER_IMAGE_TAG \
  -f alpine-upgrade/Dockerfile alpine-upgrade

  3. Create an upgraded gitlab-runner-helper image. 

    GITLAB_RUNNER_IMAGE_TYPE=gitlab-runner-helper \
GITLAB_RUNNER_IMAGE_TAG=x86_64-v17.5.0 \
docker build -t $GITLAB_RUNNER_IMAGE_TYPE:$GITLAB_RUNNER_IMAGE_TAG \
  --build-arg GITLAB_RUNNER_IMAGE_TYPE=$GITLAB_RUNNER_IMAGE_TYPE \
  --build-arg GITLAB_RUNNER_IMAGE_TAG=$GITLAB_RUNNER_IMAGE_TAG \
  -f alpine-upgrade/Dockerfile alpine-upgrade

Use SELinux in your container

Some distributions, like CentOS, Red Hat, and Fedora use SELinux (Security-Enhanced Linux) by default to enhance the security of the underlying system.

Use caution with this configuration.

Prerequisites:

  • To use the Docker executor to run builds in containers, runners need access to /var/run/docker.sock.
  • If you use SELinux in enforcing mode, install selinux-dockersock to prevent a Permission denied error when a runner accesses /var/run/docker.sock.
  1. Create a persistent directory on the host: mkdir -p /srv/gitlab-runner/config.

  2. Run Docker with :Z on volumes: 

    docker run -d --name gitlab-runner --restart always \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -v /srv/gitlab-runner/config:/etc/gitlab-runner:Z \
  gitlab/gitlab-runner:latest