How to debug a container that crashes or hangs?

If a container crashes or hangs, you can perform the following debugging steps:

1. View container logs:

docker logs <container_id>

This helps understand what happens before the crash.

2. Run the container in interactive mode:

docker run -it --entrypoint /bin/bash <image_name>

To manually check the environment and run processes step by step.

3. Attach to a running container:

docker exec -it <container_id> /bin/bash

To examine the state and run debugging commands.

4. Check resources:

There might be a lack of memory or CPU, causing the hang.

5. Use monitoring tools:

docker stats, top inside the container, or external tools.

6. Add logging and debug messages to the application:

To understand where exactly the failure occurs.

7. Check Dockerfile and configuration:

There might be an error in startup settings.

This systematic approach helps localize and resolve the issue.