Docker HelloWorld example

In this tutorial we will learn how to move the first steps with Docker images by pulling and executing a Fedora Docker image. We will also learn how to check the active running Docker containers and their status.

Having installed Docker it's time to run your first Docker image. Verify at first that Docker is running:

[francesco@dhcp-64-183 ~]$ sudo service docker status

Here is the output:

  docker.service - Docker Application Container Engine
   Loaded: loaded (/usr/lib/systemd/system/docker.service; disabled; vendor preset: disabled)
   Active: active (running) since ven 2015-09-18 16:03:40 CEST; 5min ago
 Main PID: 3726 (docker)
   CGroup: /system.slice/docker.service
       	└─3726 /usr/bin/docker daemon -H fd://

We will now pull and run a Fedora Docker image. Here 's how to do it:

$ sudo docker run -i -t fedora /bin/bash

A first check on the local repository will be performed. As we don't have any image yet it will be downloaded:

Unable to find image 'fedora:latest' locally
latest: Pulling from library/fedora
48ecf305d2cf: Pull complete
ded7cd95e059: Pull complete
library/fedora:latest: The image you are pulling has been verified. Important: image verification is a tech preview feature and should not be relied on to provide security.
Digest: sha256:49ae2d6d0b51f713a18db1c0da9fb1b5c94e92eb43cd712ba09028161ea22880
Status: Downloaded newer image for fedora:latest
Now, once downloaded, the /bin/bash shell will be executed which will put us into the Fedora shell:

Now, once downloaded, the /bin/bash shell will be executed which will put us into the Fedora shell:

[root@73f9935376c5 /]# id
uid=0(root) gid=0(root) groups=0(root)

[root@73f9935376c5 /]# env
[root@73f9935376c5 /]# pwd

[root@73f9935376c5 /]# ls
bin   dev  home  lib64   	media  opt   root  sbin  sys  usr
boot  etc  lib   lost+found  mnt	proc  run   srv   tmp  var

If we open another shell, we can check the docker ps command which will show the active docker images:

$ sudo docker ps
CONTAINER ID    	IMAGE           	COMMAND         	CREATED         	STATUS          	PORTS           	NAMES
73f9935376c5    	fedora          	"/bin/bash"     	6 minutes ago   	Up 6 minutes                        	fervent_tesla

Another command you have to learn is docker images which shows the images you have downloaded so far:

$ sudo docker images
REPOSITORY      	TAG             	IMAGE ID        	CREATED         	VIRTUAL SIZE
fedora          	latest          	ded7cd95e059    	3 months ago    	186.5 MB

When done, switch to the docker container and exit the shell:

[root@73f9935376c5 /]# exit

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