Problem Statement
What are GitLab Runners?
Explanation
GitLab Runners are agents that execute jobs defined in .gitlab-ci.yml. Runners can be shared (available to all projects), group (available to group projects), or specific (dedicated to particular project). Runners run on various platforms (Linux, Windows, macOS, Docker, Kubernetes) and can be hosted by GitLab.com (shared runners) or self-hosted by organizations.
Runner types include Shell executor (runs commands directly on runner machine), Docker executor (runs jobs in Docker containers for isolation), Kubernetes executor (runs jobs as Kubernetes pods), and VirtualBox/Parallels executors (runs jobs in VMs). Docker executor is most popular providing clean, isolated environments for each job.
Runner registration connects runner to GitLab instance using registration token from GitLab settings. After registration, runner polls GitLab for jobs matching its tags. Jobs can specify required tags targeting specific runners: tags: ['docker', 'linux']. Multiple runners provide parallel job execution and high availability. Understanding runners is essential for GitLab CI/CD execution infrastructure.
