Install and set up Gitlab CI Runner to use Docker

GitLab CI allows you to use Docker Engine to build and test docker-based projects.

We will follow the official guide: Using Docker Build

Here we choose the first method "Use shell executor".

1.Install GitLab Runner:

Here we install gitlab-ci-multi-runner on linux. Follow this official guide until "Register the runner": Install using
official GitLab repositories

2. Register the runner:

Using Docker Build is trying to register the runner in non-interactive way. Somehow it doesn't work. Here we follow the registration step in Install
using official GitLab repositories, installing in interactive way.





As we can see from the above picture, we will need to provide coordinator URL and token. They can be found in your repository at "Settings" -> "Runners":





After registering, we should be able to see the runner in "Settings" -> "Runners":





3. Install docker, set up privileges.

Just continue following Using Docker Build

4. Register multiple runners and make them run builds concurrently.

The runner config file is located at:

/etc/gitlab-runner/config.toml





The concurrent is default to 1. Here we use 3 concurrent runners, so we set it to 3.