joe, 16 days ago

Yesterday, I wrote about how I moved a mastodon bot from Pipedream to a docker container. Docker is an efficient way of running isolated little scripts like that. Today, I wanted to review some basic debugging techniques to ensure your script runs as expected.

What docker images exist on the system?

When we looked at how to dockerize a node app, I said that you create a docker image and then run it as a container. So, how do you list the docker images on a system? You run docker images.

https://i0.wp.com/jws.news/wp-content/uploads/2024/05/Screenshot-2024-05-04-at-12.37.35%E2%80%AFPM.png?resize=1024%2C856&ssl=1

What docker containers exist on the system?

If you run docker ps, you can get what containers are running, and if you run docker ps -a, it will include containers that aren’t running.

https://i0.wp.com/jws.news/wp-content/uploads/2024/05/Screenshot-2024-05-04-at-12.46.33%E2%80%AFPM.png?resize=1024%2C856&ssl=1

How do you access a container’s shell?

Like a VM or a system running on bare metal, you can get a shell inside of the docker container. The first step is knowing the container ID for the container you want a shell for. If you look at the output from the docker ps command, you can find it.

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At this point, you run docker exec -it [container id] /bin/sh to get a shell inside the container.

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Once you know that the image is there, know if it is running or not, and have a shell inside the container, you should be able to find what is wrong with your container.

Have a questions, comment, etc? Feel free to drop a comment, below.

https://jws.news/2024/debugging-a-docker-container/

#Docker