GitLab is the leading platform for hosting Git repositories, CI pipelines, and DevOps workflows. It is available as a SaaS offering on GitLab.com or as a self-managed distribution for your private use on your own hardware.
GitLab is a complex system of different components and dependencies. Installing GitLab packages directly onto your operating system will add important new services to your machine, including PostgreSQL, Redis, Gitaly, and the main Rails-based GitLab web application. 
Deploying GitLab as a Docker container is one way to avoid polluting the environment with all these components. Everything related to GitLab will live in the container, separate from the host's filesystem.
In this guide, we'll use Docker to deploy a production-ready GitLab instance that you can use to host your source code and collaborate on projects. One thing to consider before proceeding is that Docker doesn't eliminate GitLab's basic hardware requirements: you need at least 4GB of free RAM and about 10GB of unused storage.