Bits of .NET

💾 Made Changes Inside Container? Save Them!

You debugged inside container. Installed packages. Now you want to save it. docker commit creates image from running container.

📝 Basic Commit

# Start container
docker run -it ubuntu bash

# Inside container: install packages
apt-get update
apt-get install -y nginx

# Exit (Ctrl+D or exit)

# Commit changes to new image
docker commit CONTAINER_ID myapp:nginx

# Now you have image with nginx pre-installed
docker run -it myapp:nginx bash

🎯 Advanced Commit

# Commit with message and author
docker commit -m "Added nginx" -a "John Doe" CONTAINER_ID myapp:nginx

# Commit with different tag
docker commit CONTAINER_ID myapp:1.0

# Commit to specific repository
docker commit CONTAINER_ID myrepo/myapp:latest

# Pause container before commit (avoid corruption)
docker pause CONTAINER_ID
docker commit CONTAINER_ID myapp:saved
docker unpause CONTAINER_ID

# Change CMD and ENTRYPOINT during commit
docker commit --change 'CMD ["nginx", "-g", "daemon off;"]' CONTAINER_ID myapp:nginx

💡 When to Use (and Not Use)

• Good for: Debugging sessions, temporary snapshots, experimenting
• Not for: Production images (use Dockerfile for reproducibility)
• Not for: Secrets (they get committed to image)
• Prefer Dockerfile over commit for production