How to play with Docker containers on Linux

In our previous article, we have instructed about Docker installation and configuration on Major Linux distribution such as Debian, Ubuntu, LinuxMint, CentOS, RHEL, Fedora, openSUSE, Arch Linux and also we have played around with Docker Images. Now, we are going to play with Docker containers. Two types of containers are available Interactive & Daemonized. Interactive container runs in the foreground. Daemonized container runs in the background.

1) Run a Interactive Docker container

Docker Hub repository holds multiple variants of an image. say for example, ubuntu image having multiple versions like 12.04, 14.04, 14.10, 15.04 & 15.10. Each variant is identified by a tag. so whenever we run docker better to use image:tag so that we can run the specific one. If you don’t specify a variant, by default Docker will use latest version of image. To run container we need to specific the format like below.

[Docker Command Syntax Usage]
[docker [command] [flags] [arguments].....]

[Run a Docker Container]
# docker run -ti ubuntu:12.04 /bin/bash
root@0182f4f65333:/# cat /etc/*-release
VERSION="12.04.5 LTS, Precise Pangolin"
PRETTY_NAME="Ubuntu precise (12.04.5 LTS)"

Note : To exit from the interactive session, use Ctrl+p and Ctrl+q keys.

  • docker : Applicatin binary
  • run : Docker Command
  • -ti : Flags: (-t) enable terminal inside our new container, (-i) making an interactive connection
  • ubuntu:12.04 : Image with tag
  • /bin/bash : This will launch a Bash shell inside our container

1a) Run a Daemonized Docker container

For Daemonized Docker container, no need to go inside container like Interactive and we can do everything from host system itself.

# docker run ubuntu:12.04 cat /etc/issue
Ubuntu 12.04.5 LTS \n \l

2) Playing inside container

Once we launched the container which will display similar like below. Now, we are in inside container and going to execute few commands and when you’re done you can use the exit command or enter Ctrl-D to finish.

root@0182f4f65333:/# pwd

root@0182f4f65333:/# free -m

root@0182f4f65333:/# ls -lh

root@0182f4f65333:/# exit

3) List Docker Containers

When you are launching container, docker will automatically generate Unique container ID for that. Make sure you should not the container id by issuing the below command. So that we can start,stop,attach the container again when it’s required.

[List Out Running containers]
# docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
5064f89fa47b        ubuntu:12.04        "/bin/bash"         54 seconds ago      Up 53 seconds                           loving_bardeen

[List Out All containers (Include Running and Non-Running)]
# docker ps -a
CONTAINER ID        IMAGE               COMMAND             CREATED              STATUS                          PORTS               NAMES
0d602401979b        ubuntu:12.04        "cat /etc/issue"    About a minute ago   Exited (0) About a minute ago                       cranky_sinoussi
c1e38de2dd95        ubuntu              "cat /etc/issue"    2 minutes ago        Exited (0) 2 minutes ago                            grave_wing
be59a09e9af5        centos              "cat /etc/issue"    2 minutes ago        Exited (0) 2 minutes ago                            admiring_mcclintock
39f02c8657b3        centos              "cat /etc/issue"    5 minutes ago        Exited (0) 5 minutes ago                            amazing_murdock
0182f4f65333        ubuntu:12.04        "/bin/bash"         25 minutes ago       Exited (127) 23 minutes ago                         berserk_einstein
38d0baa625e9        centos:latest       "/bin/bash"         51 minutes ago       Exited (0) 44 minutes ago                           tiny_franklin
ab27e46390c2        centos              "/bin/bash"         56 minutes ago       Exited (0) 51 minutes ago                           sleepy_wing
7b0fbc7f3136        hello-world         "/hello"            About an hour ago    Exited (0) About an hour ago                        naughty_mccarthy
11fc40821bee        hello-world         "/hello"            5 weeks ago          Exited (0) 5 weeks ago                              tender_engelbart

4) Start Docker container

If you know the container ID, we can easily start,stop the container by firing the below command. Not only container id we can use auto generated name also.

# docker start [container ID or Name]

# docker start c1e38de2dd95

5) Attach/Reconnect Docker container

If you want to reconnect running container, we can easily attach it by using below command.

# docker attach [container ID or Name]

# docker attach c1e38de2dd95

6) Stop Docker container

If you want to stop the running container, use the below command to stop it.

# docker stop [container ID or Name]

# docker stop c1e38de2dd95

7) Delete Docker container

You have played around the container and want to Remove/Delete, you can do by running below commands. Make sure the container should be stop before proceeding removal.

# docker rm [container ID or Name]

# docker rm c1e38de2dd95

8) Stop Docker container from Host

To stop running container from Master Host.

# docker kill [container ID or Name]

# docker kill 5064f89fa47b


About Magesh Maruthamuthu

Love to play with all Linux distribution

View all posts by Magesh Maruthamuthu

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