Docker

Containers

Basics

1. Run container (e.g. nginx)
   • docker run nginx
2. Run container with specific version (tag)
   • docker run <container_name>:<tag>
   • docker run redis:4.0
3. List containers
   • Running
     • docker ps
   • All
     • docker ps -a
4. Stop container
   • docker stop <container_id/name>
5. Remove container
   • docker rm <container_id/name>
6. Map Ports
   • Map Docker Host port to Docker Container port
     • docker run -p <host_port>:<container_port> <container_id/name>
   • E.g. Map port 80 of Docker Host to port 5000 of Docker Container
     • docker run -p 80:5000 my_container
7. Map Volumes
   • Map Docker Host Volume to Docker Container Volume
     • docker run -v <host_path>:<container_path> <container_id/name>
     • docker run -v /opt/datadir:/var/lib/mysql mysql
8. Get more detailed info of container
   • docker inspect <container_id/name>
9. Show Container logs
   • docker logs <container_id/name>
10. Set Environmental Variables
    • docker run --env <variable>=<value> <container_id/name>
    • docker run --env JAVA_VERSION=11 my_container
    • --env ~ -e
11. Display Environmental Variables
    • Use docker inspect command

Images

1. Build docker image
   • docker build <path_of_Dockerfile>
   • docker build .
2. Tag docker image you are building
   • docker build . -t <repository>/<image_name>
3. Tag docker image you have built
   • docker tag <image> <repository>/<image_name>:<tag>
4. Download image
   • docker pull <image_name>
5. Show downloaded images
   • docker images
6. Download image into computer
   • docker image save <image> > image.tar
7. Show image history (some commands and sizes)
   • docker history <image>
8. Remove image
   • docker rmi <image_name>

Commands

1. Run container with command
   • docker run ubuntu <command>
   • docker run ubuntu sleep 5
2. Run command on a running container
   • docker exec <container_id/name> <command>
   • docker exec my_ubuntu cat /etc/hosts
3. Run container in detached mode
   • docker run -d <container_id/name>
4. Attach to running container
   • docker attach <container_id/name>
5. Enable interactive mode to make container receive input
   • docker run --interactive <container_id/name>
   • --interactive ~ -i
6. Attach to terminal (to see its output)
   • docker run --tty <container_id/name>
   • --tty ~ -t
7. Run container in combined mode to have both terminal input and output
   • docker run -it <container_id/name>

COMMANDs and ENTRYPOINTs

1. Specifying Commands in Dockerfile
   • Shell form
     • CMD <command> <param>
   • JSON Array form
     • CMD ["<command>", "param"]
2. CMD vs ENTRYPOINT
   • CMD allows to override Dockerfile command and arguments
     • docker run my_container <command> <arguments>
   • ENTRYPOINT only appends arguments into Dockerfile
     • docker run my_container <arguments>
3. Set default arguments
   • It must be JSON Array form
   • You provide both ENTRYPOINT and CMD

     • ENTRYPOINT ["sleep"]
       CMD ["5"]
       

4. Override ENTRYPOINT
   • docker run --entrypoint <command> <image> <args>
   • docker run --entrypoint sleep2 ubuntu-sleeper 10

Networking

Network: Bridge

• Default network
• Network within Docker Host, allows communication between all containers
• You need to map Ports to access containers
• By default one Bridge Network is created
  • If you need more, you have to specify this explicitly

Network: Host

• Ports are shared with the “real” network
• You don’t have Network isolation in this case (so beware of port collision with “real” network)
• Also you can’t run multiple containers on the same container ports, as they are now published
• --network=host

Network: None

• No network - totally isolated
• --network=none

Commands

1. Create new Network
   • docker network create --driver <driver> --subnet <a.b.c.d/n> <network_name>
   • docker network create --driver bridge --subnet 182.18.0.0/16 my_network
2. Embedded DNS
   • All Docker containers are accessible by their names
   • This DNS runs at 127.0.0.11
3. Show Network info of container
   • Use docker inspect