Dockerイメージとコンテナの管理

Two core concepts: an image is a read-only template (like a class), and a container is a running instance of it (like an object). One image, many containers.

List the images on your machine with docker images. Each row shows the repository, tag, id, and size.

docker ps shows running containers; add -a to include stopped ones too.

docker inspect prints detailed JSON about a container or image — its config, network, mounts, and more.

Read a container's output with docker logs. Add the -f flag to follow the stream live, like tail -f.

docker stop halts a container gracefully (SIGTERM, then SIGKILL after a grace period) and docker start brings it back.

Delete a stopped container with docker rm. You can't remove a running one unless you force it with -f.

Remove an image with docker rmi. It fails if any container still references it, so clear those dependent containers first.

docker exec runs a command inside a running container. With -it you get an interactive shell to poke around.

Stopped containers and dangling images pile up over time. docker system prune reclaims all that space in one command.

Give a container a friendly handle with --name at run time, so you reference it by name instead of a random id.

Recap: list with docker images and ps -a, dig in with inspect and logs, control lifecycle via stop/start/rm/rmi, and clean up with system prune.