Debugging & Monitoring Docker Containers

1. Introduction

Docker makes it easy to run applications, but sometimes containers fail to start, crash, or use too many resources.

Just like checking your car’s dashboard 🚗 to see fuel levels or errors, Docker provides built-in tools to debug and monitor containers.

In this guide, you’ll learn how to check logs, monitor resources, debug failures, and troubleshoot issues using simple commands.

2. Checking Container Logs & Status

Docker logs help you understand what’s happening inside a container.

Viewing Logs of a Running Container

docker logs <container_id>

Example:

docker logs myapp

✅ This shows the container’s output (errors, warnings, or normal activity).

Checking a Container’s Status

docker ps -a

This lists all containers and their status:

CONTAINER ID  IMAGE   STATUS          PORTS
123abc456def  myapp   Exited (1) 2m ago   8080->80/tcp

🚨 If a container has "Exited (1)" status, it means something went wrong!

3. Monitoring Resource Usage with docker stats

To check CPU, memory, and network usage of running containers:

docker stats

Example output:

CONTAINER   CPU %   MEM USAGE / LIMIT   NET I/O
myapp       5.3%    120MB / 512MB       2MB / 1MB

✅ This helps identify high-memory or CPU-consuming containers.

4. Debugging Failed Builds & Crashes

If your docker build command fails, check for errors:

docker build -t myapp .

🚨 Common issues:
❌ Missing files – Ensure all files are in the correct location.
❌ Permission errors – Run with sudo if needed.
❌ Incorrect syntax in Dockerfile – Double-check commands.

To see why a container crashed, check its logs:

docker logs <container_id>

5. Using docker inspect for Troubleshooting

The docker inspect command provides detailed container information.

Check Container Details

docker inspect <container_id>

✅ This shows network settings, volume mounts, and configuration details.

6. Conclusion

Now you can debug & monitor Docker containers like a pro! 🎉

✅ Check logs with docker logs
✅ Monitor resources with docker stats
✅ Debug build failures & crashes
✅ Use docker inspect for detailed info

Try these commands next time you face an issue! 🚀