Docker Compose: up --build Command

Overview

docker compose up --build is used to build (or rebuild) and start Docker containers as defined in your docker-compose.yml file. This ensures your containers use the latest code and configuration.

Command Breakdown

When to Use --build

✅ Use --build when:

• You’ve updated your Dockerfile.
• You’ve changed your application code and need it reflected in the container.
• You suspect the existing image is outdated or corrupted.

❌ Avoid --build when:

• No changes have been made to the code or Dockerfile.
• You want to save time (rebuilding can be slow).

Example Workflow

1. First Run (or after changes):

docker compose up --build

Builds images and starts containers with the latest changes.

2. Normal Start (no changes):

docker compose up

Uses cached images for faster startup.

3. After Code or Dockerfile Updates:

docker compose up --build

Ensures containers use the latest code and configuration.

Tips

• Use --build sparingly to save time during development.
• To rebuild only a specific service, use:

  docker compose build <service_name>
  docker compose up
  

• Check your docker-compose.yml and Dockerfile for changes before deciding to rebuild.

Written by A.M. Rinas