🚀 How to Use Linux Parallel to Speed Up CI

When your CI pipeline takes too long, it often means too many tasks are running sequentially. The tool GNU Parallel allows you to execute commands in parallel, saving a lot of time — especially for builds, tests, or deployments.

🧩 What Is GNU Parallel?

GNU Parallel is a command-line utility for running multiple shell commands at once. It splits your workload into parts and executes them across available CPU cores.

Example:

cat jobs.txt | parallel

Each line in jobs.txt is treated as a separate job and executed in parallel.

⚙️ Typical Use in CI

Let’s say you have multiple integration test suites:

parallel ::: "pytest tests/api" "pytest tests/db" "pytest tests/ui"

This runs all three test suites simultaneously.

Or build multiple Docker images at once:

parallel docker build -t myapp-{} ./{} ::: frontend backend worker

Why It’s Great for CI/CD

  • Reduces build and test times
  • Fully compatible with most CI runners (GitLab, Jenkins, GitHub Actions)
  • Simple and lightweight — no need for extra dependencies

🧭 Pro Tip

Combine parallel with caching and conditional steps in your CI to achieve the best performance. Example for GitLab CI:

build:
  script:
    - parallel ::: "make build-frontend" "make build-backend"

With this, your CI/CD pipeline will feel twice as fast — with almost no extra effort.