GitLab CI/CD

Automate your software delivery pipeline with GitLab's integrated CI/CD system.

When to Use This Skill

Use this skill when:

• Setting up CI/CD pipelines in GitLab
• Configuring GitLab runners (shared or self-hosted)
• Creating multi-stage deployment pipelines
• Implementing GitLab Auto DevOps
• Managing CI/CD variables and secrets

Prerequisites

• GitLab repository (gitlab.com or self-hosted)
• Basic understanding of YAML
• For self-hosted runners: Linux server or Kubernetes cluster

Pipeline Configuration

Create .gitlab-ci.yml in repository root:

stages:
  - build
  - test
  - deploy

variables:
  NODE_VERSION: "20"

build:
  stage: build
  image: node:${NODE_VERSION}
  script:
    - npm ci
    - npm run build
  artifacts:
    paths:
      - dist/
    expire_in: 1 hour

test:
  stage: test
  image: node:${NODE_VERSION}
  script:
    - npm ci
    - npm test
  coverage: '/Coverage: \d+\.\d+%/'

deploy:
  stage: deploy
  script:
    - ./deploy.sh
  environment:
    name: production
    url: https://example.com
  only:
    - main

Job Configuration

Rules-Based Execution

deploy:
  script: ./deploy.sh
  rules:
    - if: $CI_COMMIT_BRANCH == "main"
      when: manual
    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
      when: never
    - when: on_success

Parallel Jobs

test:
  stage: test
  parallel: 3
  script:
    - npm test -- --shard=$CI_NODE_INDEX/$CI_NODE_TOTAL

Matrix Builds

test:
  stage: test
  parallel:
    matrix:
      - NODE_VERSION: ["18", "20", "22"]
        OS: ["alpine", "slim"]
  image: node:${NODE_VERSION}-${OS}
  script:
    - npm test

Caching

cache:
  key:
    files:
      - package-lock.json
  paths:
    - node_modules/
  policy: pull-push

build:
  cache:
    key: build-cache
    paths:
      - .cache/
    policy: pull

Artifacts

build:
  artifacts:
    paths:
      - dist/
      - coverage/
    reports:
      junit: junit.xml
      coverage_report:
        coverage_format: cobertura
        path: coverage/cobertura.xml
    expire_in: 1 week
    when: always

Environments and Deployments

deploy_staging:
  stage: deploy
  script:
    - deploy --env staging
  environment:
    name: staging
    url: https://staging.example.com
    on_stop: stop_staging

stop_staging:
  stage: deploy
  script:
    - undeploy --env staging
  environment:
    name: staging
    action: stop
  when: manual

Docker Builds

build_image:
  stage: build
  image: docker:24
  services:
    - docker:24-dind
  variables:
    DOCKER_TLS_CERTDIR: "/certs"
  script:
    - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
    - docker build -t $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA .
    - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA

GitLab Runners

Install Runner

# Download and install
curl -L https://packages.gitlab.com/install/repositories/runner/gitlab-runner/script.deb.sh | sudo bash
sudo apt install gitlab-runner

# Register runner
sudo gitlab-runner register \
  --url https://gitlab.com/ \
  --registration-token TOKEN \
  --executor docker \
  --docker-image alpine:latest

Runner Configuration

# /etc/gitlab-runner/config.toml
[[runners]]
  name = "docker-runner"
  url = "https://gitlab.com/"
  token = "TOKEN"
  executor = "docker"
  [runners.docker]
    image = "alpine:latest"
    privileged = true
    volumes = ["/cache", "/var/run/docker.sock:/var/run/docker.sock"]

Runner Tags

build:
  tags:
    - docker
    - linux
  script:
    - make build

CI/CD Variables

Protected Variables

Define in Settings > CI/CD > Variables:

• AWS_ACCESS_KEY_ID (protected, masked)
• AWS_SECRET_ACCESS_KEY (protected, masked)

Using Variables

deploy:
  script:
    - aws s3 sync dist/ s3://$S3_BUCKET
  variables:
    AWS_DEFAULT_REGION: us-east-1

Include and Extend

Include Templates

include:
  - template: Security/SAST.gitlab-ci.yml
  - project: 'group/shared-ci'
    file: '/templates/deploy.yml'
  - local: '/ci/jobs.yml'

Extend Jobs

.base_job:
  image: node:20
  before_script:
    - npm ci

build:
  extends: .base_job
  script:
    - npm run build

test:
  extends: .base_job
  script:
    - npm test

Multi-Project Pipelines

trigger_downstream:
  stage: deploy
  trigger:
    project: group/downstream-project
    branch: main
    strategy: depend

Common Issues

Issue: Pipeline Stuck

Problem: Jobs stay pending Solution: Check runner availability and tags matching

Issue: Docker-in-Docker Fails

Problem: Cannot connect to Docker daemon Solution: Use docker:dind service with proper TLS configuration

Issue: Cache Not Working

Problem: Cache misses between jobs Solution: Verify cache key and ensure runners share distributed cache

Best Practices

• Use rules instead of only/except for complex conditions
• Leverage GitLab's built-in security scanning templates
• Use job dependencies to optimize pipeline speed
• Implement review apps for merge requests
• Cache dependencies aggressively
• Use artifacts for passing data between stages

Related Skills

• github-actions (github-actions) - GitHub CI/CD alternative
• argocd-gitops (argocd-gitops) - GitOps deployments
• container-registries (container-registries) - Registry management

Limitations

• Guidance executes against real environments: confirm target, blast radius, and rollback plan before applying anything.
• Never deploy to production without explicit approval. Docs-only import: upstream scripts and templates not bundled.

Example

git status && git diff --stat
kubectl diff -f manifest.yaml

Adapted from BagelHole/DevOps-Security-Agent-Skills (MIT); frontmatter, When to Use/Limitations, and safety boundaries added for upstream compliance. Docs-only import: helper scripts and templates not bundled.