Docker Basic Command

Command

1. Windows Sub linux Ubuntu start docker
   sudo service docker start
2. show basic information of docker engine
   docker info
3. show local images
   docker image ls
4. remove image
   docker rmi {repo:tag} or docker rmi {image_id}
docker image prune remove all not used
5. show image config
   docker image inspect hello-world hello-world is the image name.
   ContainerConfig.Cmd is important.
6. build image
   docker build -t karl/hello:1.0 . need a Dockerfile in current directory
7. pull from a registry other than docker hub
   docker pull private-docker-registry.example.com/nginx
8. docker start a container
   docker run -p 80:80 nginx
docker run -it --name <container-name> <image-name> run at inrerative mode

   -p the port on the Docker host : the port within the container which is showed on "Config.ExposedPorts" in image inspect
   docker start -ai container-name start docker container interactively

docker run --entrypoint ifconfig bash run image "bash" but overwrite the default command by --entrypoint ifconfig
docker run --entrypoint ping bash google.com -c1 overwrite default command with parameters

1. show running containers
   docker ps
2. show all containers
   docker ps -a
3. tag an image
   docker tag <image id> <repository:tag name>
docker tag <old tag> <new tag>
4. Remove all stopped containers
   docker container prune -f
docker rm $(docker ps --filter status=exited -q)
5. Copy files from container
   docker cp <container-id>:/path-in-container <path-in-local>
docker cp <container-name>:/path-in-container <path-in-local>
6. run sh in container
   docker exec -it <container name> sh

Dockerfile Instructions

1. WORKDIR /path/to/directory : sets the current working directory for the RUN, CMD, ENTRYPOINT, COPY, and ADD instructions.
   it is the path in the docker container.

2. ADD <source> <destination>
COPY <source> <destination>

3. RUN
   1>shell form:to use shell variables, subcommands, command pipes, and command chains
   RUN <command>

   A program started in shell form will run as a subcommand of /bin/sh -c. This means the executable will not be running as PID and will not receive UNIX signals. As a consequence, a Ctrl+C to send a SIGTERM will not be forwarded to the container and the application might not exit correctly.

   2>exec form
   RUN ["executable", "parameter 1", " parameter 2"]

4. Docker creates a new layer whenever it encounters RUN, COPY, or ADD instructions.
   it is best to chain the update and installs,
   RUN apt-get update && apt-get install -y
   pkg1
   pkg2 \

5. You can override the CMD instruction by passing arguments to the docker run command.

   CMD ["executable","param1","param2"] (exec form)
   CMD ["param1","param2"] (as default parameters to ENTRYPOINT)
   CMD command param1 param2 (shell form)
   

6. ENTRYPOINT　set the program to run, pass the parameter in the command line.
   ENTRYPOINT ["curl", "-s"]
docker run sathyabhat/curl wttr.in

7. ENV <key>=<value> ...
   set env value at run:
   docker run -it -e LOGS_DIR="/logs" -e APPS_DIR="/opt" karl/hello:0.1

8. The EXPOSE instruction tells Docker that the container listens for the specified network ports at runtime.
   EXPOSE 53/tcp
EXPOSE 53/udp
   Default is TCP

9. Dockerfile Sample

FROM python:3.11
LABEL author="Karl"
LABEL description="An example Dockerfile for python"
RUN echo `uname -rv` > $HOME/kernel-info
RUN apt-get update
WORKDIR /app
COPY hello.py hello.py
ENTRYPOINT ["python"]
CMD ["/app/hello.py"]