Docker

Docker runs apps as isolated containers built from images, defined via Dockerfile, and managed via Docker Compose for multi-service apps.

1. Mental flow (must know)

Dockerfile → Image → Container → Running App
           (build)   (run)

2. Context

Controls which Docker engine you are using.

docker context ls
docker context show
docker context use desktop-linux   # or default

If you mess this up → containers “disappear”.

3. Daily essential commands

Check status

docker ps          # running containers
docker ps -a       # all containers
docker images      # stored images

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Run / stop containers

docker run IMAGE                  # start container
docker run -d IMAGE               # background
docker run -it IMAGE bash         # shell access

docker stop CONTAINER
docker start CONTAINER
docker restart CONTAINER
docker rm CONTAINER

Debug

docker logs CONTAINER
docker exec -it CONTAINER bash
docker inspect CONTAINER

4. Docker Compose

Used for full stacks (API + DB + Redis + workers)

docker compose up -d      # start everything
docker compose down       # stop everything
docker compose ps         # check services
docker compose logs       # see logs
docker compose build      # rebuild images

This will build the container from the image then start it

docker compose up <name of container> --build

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5. Images (build system)

docker build -t name .    # build image
docker pull image         # download image
docker rmi image          # delete image

6. System cleanup (optional but useful)

docker system df
docker system prune
docker image prune

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7. Volumes (data persistence)

docker volume ls
docker volume create NAME
docker volume rm NAME

8. Networks (containers talking)

docker network ls
docker network inspect NAME

9. Your real debugging checklist (use this always)

If something “doesn’t work”:

docker context show
docker ps -a
docker compose ps
docker logs <container>