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Docker in Action, Second Edition: Starting learning Docker following hands-on instructions:

  1. Running software in containers for isolation:

  • Docker builds container using 10 major system features:

    Feature Illustration
    PID namespace Process identifiers and capabilities.
    UTS namespace Host and domain name.
    MNT namespace Filesystem access and structure.
    IPC namespace Process communication over shared memory.
    NET namespace Network access and structure.
    USR namespace User names and identifiers.
    chroot syscall Controls the location of the filesystem root.
    cgroups Resource protection.
    CAP drop Operating system feature restrictions.
    Security modules Mandatory access controls.

  • Docker use those features as above to build containers at runtime, but it uses another set of technologies to package and ship containers.

  • Example:

    # `-d/--detach` := running new container as a background-process, this means that the program started but isn't attached in our terminal.
docker run --detach --name web nginx:latest

docker run -d --name mailer dockerinaction/ch2_mailer

# NOTE: Runnning an interactive containers with the terminal:
# `-i/--interactive` := Keep the standard-input-stream (`stdin`) open for the container even if no terminal is attached.
# `-t/--tty` := To allocate a virtual terminal for the container, which will allow users to pass signals to the container.
# `--link` := Add link to another container.
docker run -it --link web:web --name web_test busybox:1.29
# -> Access: `/bin/sh` inside `busybox` container.
# -> Run this command: `wget -O - http://web:80/` (remember to disable http(s)_proxy || HTTP(S)_PROXY if your Docker configuration have one).
# NOTE: `wget -O <FILE> <URL>` := Save to <FILE> ('-' for stdout).

docker run -it --name agent --link web:insideweb --link mailer:insidemailer dockerinaction/ch2_agent
    • NOTE:
      • Everytime you run docker run and creare a new container, that new container will get an unique identifier (blob of characters).
      • Running detached container suitable with programs that sit quietly in the background. That type of program is called as a daemon, or a service.
      • A daemon generally interacts with other programs or humans over a network or some other communication channel.

  • List of some basic commands that can easily take effect on a container:

    Action Command Display information
    Listing docker ps -a - The container ID.
    - The image used.
    - The command executed the container.
    - The time since the container was created.
    - The duration that the container has been running.
    - The network ports exposed by the container.
    - The name of the container itself.
    Stop docker stop <CONTAINER_NAME>/<CONTAINER_ID>
    docker stop $(docker ps -aq)
    Restart docker restart <CONTAINER_NAME>/<CONTAINER_ID>
    docker restart $(docker ps -aq)
    docker restart $(docker ps -aq | sort -r)
    Logging docker logs <CONTAINER_NAME>/<CONTAINER_ID
    for con in $(docker ps -a --format '{{.Names}}'); do docker logs $con; done