Debugging with Logs¶

Problem¶

Something is not working, and you need to find out what the container is actually doing.

Symptoms¶

A container errors, returns an unexpected result, or behaves differently than you expect.

The First Move¶

Almost every Docker problem starts here. Read what the container printed.

docker logs CONTAINER_NAME

Useful Variations¶

Follow logs live as they happen.

docker logs -f CONTAINER_NAME

Show only the most recent lines.

docker logs --tail 50 CONTAINER_NAME

For Compose, view all services together.

docker compose logs

Reading the Output¶

• A stack trace or error message points directly at the cause
• "connection refused" or "could not resolve host" suggests a networking problem
• No output at all may mean the app logs to a file instead of the screen

Why This Matters¶

A browser or client often shows only a vague error. The logs show the real cause. When in doubt, check the logs before changing anything.

Related¶

• Inspecting Containers