In this guide, we’ll explore how to use the GitLab container registry, including setting it up, pushing and pulling images, and integrating it into CI/CD pipelines. By the end, you’ll be equipped to manage container images effectively for your projects.

What Is the GitLab Container Registry?

The GitLab container registry is a private, Docker-compatible registry that allows you to store and manage container images within your GitLab projects. It integrates seamlessly with GitLab CI/CD and provides role-based access control for managing images securely.

Key Features:

  • Built-In Integration: Available in all GitLab projects.
  • Private and Secure: Provides fine-grained access controls.
  • CI/CD Integration: Automate building, pushing, and pulling images in pipelines.
  • Efficiency: Reduces context switching by managing images within GitLab.

Step 1: Enabling the Container Registry

The container registry is enabled by default in most GitLab projects. To verify:

  1. Navigate to your GitLab project.
  2. Go to Settings > General > Visibility, Project Features, Permissions.
  3. Ensure that Container Registry is enabled.

Step 2: Authenticating with the Registry

To push and pull images, authenticate to the GitLab container registry using your GitLab credentials or a personal access token.

Login Command:

docker login registry.gitlab.com

You’ll be prompted to enter your GitLab username and password (or personal access token).

Step 3: Building and Pushing Images

Here’s how to build a Docker image and push it to the GitLab container registry:

  1. Build the Image: 
    docker build -t registry.gitlab.com//: .
    Replace <namespace> with your GitLab namespace (username or group name), <project-name> with the project name, and <tag> with the image tag.
  2. Push the Image: 
    docker push registry.gitlab.com//:

Example:

docker build -t registry.gitlab.com/my-user/my-project:latest .
docker push registry.gitlab.com/my-user/my-project:latest

Step 4: Pulling Images

To pull an image from the GitLab container registry, use the docker pull command:

docker pull registry.gitlab.com//:

Example:

docker pull registry.gitlab.com/my-user/my-project:latest

Step 5: Integrating with GitLab CI/CD

You can use the container registry in your GitLab CI/CD pipelines to build and deploy applications. Here’s an example pipeline configuration:

stages:
  - build
  - deploy

build-image:
  stage: build
  script:
    - docker build -t registry.gitlab.com//:latest .
    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" "$CI_REGISTRY"
    - docker push registry.gitlab.com//:latest

deploy-image:
  stage: deploy
  script:
    - docker pull registry.gitlab.com//:latest
    - docker run -d -p 80:80 registry.gitlab.com//:latest

GitLab provides predefined CI/CD variables, such as $CI_REGISTRY, $CI_REGISTRY_USER, and $CI_REGISTRY_PASSWORD, to simplify authentication in pipelines.

Managing Images in the GitLab UI

You can view and manage container images directly in the GitLab interface:

  1. Navigate to Packages & Registries > Container Registry in your project.
  2. View a list of all images and their tags.
  3. Delete outdated or unused images to free up storage space.

Best Practices for Using the GitLab Container Registry

  • Tag Images Properly: Use meaningful tags like latest, v1.0.0, or staging to organize your images.
  • Clean Up Unused Images: Regularly delete outdated images to conserve storage.
  • Secure Access: Use fine-grained access controls to restrict who can push or pull images.
  • Integrate with CI/CD: Automate image building and deployment in your pipelines for efficiency.
  • Monitor Usage: Keep track of storage usage and clean up unnecessary images periodically.

Common Use Cases

  • Application Deployment: Use container images to deploy your application in a consistent environment.
  • Microservices: Manage and deploy multiple microservices as Docker containers.
  • Testing Environments: Use images to set up isolated testing environments.

Conclusion

GitLab’s container registry is a powerful tool for managing Docker images directly within your projects. Its integration with CI/CD pipelines and robust access controls make it an essential feature for modern DevOps workflows. Start using the GitLab container registry today to streamline your containerized application development and deployment process.