Module 2: Play with Ubuntu image

In this section, we are going to run a Ubuntu container and play with the docker run command.

$ docker pull ubuntu:18.04

The pull command fetches the ubuntu image from Docker Hub and store into the system.

$ sudo docker images

REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
ubuntu              18.04               a2a15febcdf3        2 weeks ago         64.2MB
hello-world         latest              fce289e99eb9        8 months ago        1.84kB

Docker Run

Let's run an Ubuntu container based on this image, using docker run

$ sudo docker run ubuntu:18.04

Nothing happened! But it is not a BUG. When running run command, Docker client will create the contwainer from image then runs a command in that container. In above case, we did not provide a command, so container ran an empty command and existed.

Now, try again with the command

$ sudo docker run ubuntu:18.04 echo 'hello, I am ubuntu'
hello, I am Ubuntu

Finnaly, it ran echo command in the Ubuntu container and exited.

Docker PS

Next, to show all containers that are running, using docker ps

$ sudo docker ps

CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

We got the empty list since no containers are running. Let's try again with new parameter -a

$ sudo docker ps -a

CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                     PORTS               NAMES
5edf418a12f2        ubuntu:18.04        "echo 'hello, I am U…"   7 minutes ago       Exited (0) 6 minutes ago                       clever_hertz

Do notice that the STATUS column shows that container exited a few minute ago.

How to access container

$ sudo docker run -it ubuntu:18.04 bash

root@82ba45277562:/# ls
bin  boot  dev  etc  home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var
root@82ba45277562:/#

Running this command with the -it flags attaches us to an interactive tty in the container. Now we try to run commands to install nano in the container

root@82ba45277562:/# nano text1.txt
bash: nano: command not found
root@82ba45277562:/# apt-get update
...

root@82ba45277562:/# apt-get install nano
Reading package lists... Done
...

root@82ba45277562:/# nano -V
 GNU nano, version 2.9.3
 (C) 1999-2011, 2013-2018 Free Software Foundation, Inc.
 (C) 2014-2018 the contributors to nano
 Email: nano@nano-editor.org	Web: https://nano-editor.org/
 Compiled options: --disable-libmagic --disable-wrapping-as-root --enable-utf8

Clean up containers

Find the docker container which wants to remove

$ sudo docker ps -a

In order to clean up / remove container, we use the docker rm command

$ sudo docker rm 11048001c4af 82ba45277562
11048001c4af
82ba45277562

To delete all exited containers, using the following

$ sudo docker rm $(sudo docker ps -a -q -f status=exited)
ea21c89eda2b
c1160c25919b
ec3a52538290
cef1e24c1851

The -q parameter, only return the IDs and -f is filter.

In the latest of Docker version, the docker container prune command can be used to achieve the same effect.

$ sudo docker container prune

Are you sure you want to continue? [y/N] y
Deleted Containers:
f1cf74322599388df6bf6ea4752ed91258026b5d8eba812d3e5325dfa88ce0b6
bccd0fa7ebb04f7a69c3120dc6daf7bb18230b02d9e634e0b32bc6c0167c54a1
d53835eca30a7304c0862660c4322096f4a4bfc12d82b5eca8fa9863b7446138

Total reclaimed space: 0B

Clean up images

$ sudo docker rmi ubuntu:latest
Untagged: ubuntu:latest

Or

$ sudo docker image prune
WARNING! This will remove all dangling images.
Are you sure you want to continue? [y/N]

← Set up your Docker environment Create and run a Docker application →

# Module 2: Play with Ubuntu image

# Docker Run

# Docker PS

# How to access container