I have some questions regarding Gitlab Server & Gitlab Runner.
Must GitLab Runner be installed to perform CI/CD deployments?
Must GitLab Server be installed for GitLab Runner?
Must GitLab Runner be installed on the same server as Gitlab if Gitlab Runner requires Gitlab server?
Gitlab Runners are a software component that can execute Gitlab CI jobs. Runners can operate on a stand alone server (or desktop/laptop), in docker, in kubernetes, and with minimal requirements. A runner must connect to the server to accept jobs from the server it is registered with, so a gitlab runner is dependent on a Gitlab server. It's actually sensible to have different runners executing jobs in the same pipeline.
A server may have many runners in many different network locations. About the only place you SHOULD NOT deploy a gitlab runner is on your gitlab server. Gitlab.com provides runners some for free and some for pay, but they are generally deployed on separate infrastructure, because this is just good design.
Gitlab Runners and Gitlab CI jobs and pipelines are good way to implement CI/CD deployments. They are not the only way, however. They are the way supported by Gitlab, and all things considered, I'd say they are a very good choice. Lots of other CI/CD tools exist, however, and different repositories on the same server can make different choices about how to implement their CI/CD pipeline.
