Which Docker image to use for GitLab Runner?
To use GitLab Runner with Docker you need to register a new Runner to use the docker executor. The registered runner will use the ruby:2.6 Docker image and will run two services, postgres:latest and mysql:latest , both of which will be accessible during the build process.
What is GitLab runner for?
GitLab runner is a build instance which is used to run the jobs over multiple machines and send the results to GitLab and which can be placed on separate users, servers, and local machine. You can register the runner as shared or specific after installing it.