Viewing container logs in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Viewing logs of a running container

You have a Docker container named webapp running. Which command shows the logs of this container?

A docker logs webapp

B docker show logs webapp

C docker container logs webapp

D docker get logs webapp

💡 Hint

The command to see logs starts with docker logs.

The correct command to view logs of a container is docker logs [container_name]. Other options are invalid commands.

💻 Command Output

intermediate

Viewing real-time logs with follow option

You want to see live logs from a container named db as they are generated. Which command will do this?

A docker logs db -r

B docker logs --tail=0 db

C docker logs -f db

D docker logs db --live

💡 Hint

The option to follow logs live is a single letter.

The -f or --follow option streams logs live. Other options are invalid or do not stream logs.

❓ Configuration

advanced

Limiting log output to recent lines

You want to see only the last 50 lines of logs from a container named api-server. Which command achieves this?

A docker logs -n 50 api-server

B docker logs --tail 50 api-server

C docker logs --last 50 api-server

D docker logs api-server --limit 50

💡 Hint

The option to limit lines is --tail.

The --tail option followed by a number shows that many recent lines. Other options are invalid or do not exist.

❓ Troubleshoot

advanced

Error when viewing logs of a stopped container

You run docker logs myapp but get the error: Error: No such container: myapp. What is the most likely cause?

A You must use <code>docker logs -a myapp</code> to see logs of stopped containers

B You need to add <code>-f</code> option to see logs

C Docker daemon is not running

D The container named <code>myapp</code> does not exist or was removed

💡 Hint

Check if the container is listed with docker ps -a.

The error means Docker cannot find a container named myapp. It may have been removed or never created. The -f option or -a do not fix this error.

✅ Best Practice

expert

Efficiently managing large container logs

Your container produces very large logs. Which approach is best to avoid filling disk space while still being able to view recent logs?

A Configure Docker logging driver to use log rotation with size limits

B Manually delete log files in /var/lib/docker/containers regularly

C Use <code>docker logs --tail 10</code> every time to limit output

D Stop the container frequently to clear logs

💡 Hint

Docker supports built-in log rotation settings.

Setting a logging driver with rotation and size limits prevents disk from filling up automatically. Manual deletion or stopping containers is inefficient and risky. Using --tail limits output but does not reduce log file size.