Container management

docker container management

Container creation#

• Create a docker container using CentOS image
  • -it flag means executing container with attaching their terminal (TTY) and standard input (STDIN)
  • --name flag makes us set a human readable name of the container
    • You can easily manage the container if it is named.
    • If you don’t specify a name of the container, it uses a commit tag as the name and you can use 3 or 4 leading alphanumeric of the name hash to manage it.

docker run --name centos -it centos

• Detach the attached TTY
  • You hit Ctrl-p Ctrl-q to exit the attached terminal without shutting down the container.
  • If you type and run exit in your attached terminal, it makes the container turned off. In order to turn on it, use docker start centos.
    • Refer to the next section to connect the restarted container.

Connect to your container#

Check container’s status#

• Use docker ps command to list running containers.
• For listing all containers event if not running, run docker ps -a.
• You can retrieve the container named by centos by docker ps -a -f name=centos.
  • For more details on filter, refer to filter section in the official site.
  • Instead of the filter, you can use grep as docker ps -a | grep centos.
• You can get the minimum information by docker ps --format "table {{.Names}}\t{{.Status}}\t{{.Ports}}".
  • You can learn about format on docker format section in the official site.

Connect into the container#

• exec sub-command helps us to connect into the container.
  • You must add -it flags to connect it, the following command shows execution of bash command to connect to the container.

docker exec -it centos bash

• You can use attach sub-command to attach your container.
  • Note that attach sub-command makes you directly attach to running environment. It means that if you run exit or invoke SIGTERM, it terminates your container. Therefore, you use Ctrl-p Ctrl-q shortcut to detach the container.

Docker hub#

What is docker hub?#

• Docker image portal
  • In order to search docker images, you can use search sub-command.
    • Also, you can containerize the searched images.

docker search ubuntu

Using the docker hub#

• Docker hub

  • Docker hub is a website for searching docker images.
    • In the results, you can find tags of an image in tags tab.

  

Using docker image and tags#

• Searching docker images on docker hub
  • In tags tab, find a tag you want to containerize.
  • In order to containerize an image, describe the image and tag formed by {image repository}:{tag}.
    • The below command show a way to run ubuntu 20.04.

docker run -it --name ubuntu ubuntu:20.04