Introduction to Docker
Docker and more generic Linux containers technology are a hot topic these days. The website says “for developers and sysadmins”, I am neither of the two but I can still find some useful applications for containers as a Network Engineer.
Let’s start from the basics.
Install docker and first run
We can apt-get to install docker on Ubuntu Linux:
apt-get install docker.io
Now start docker service:
service docker start
That was easy.
Now we can download an Ubuntu 15.04 container from the official Ubuntu repository:
docker pull ubuntu:15.04
It will take some time, that’s about 130MB.
Pulling repository ubuntu Status: Downloaded newer image for ubuntu:15.04
Check if the new image is available in the local images list:
docker images REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE ubuntu vivid bd94ae587483 17 hours ago 131.3 MB ubuntu vivid-20150427 bd94ae587483 17 hours ago 131.3 MB ubuntu 15.04 bd94ae587483 17 hours ago 131.3 MB
Run the container and start bash inside of it:
docker run -i -t ubuntu:15.04 /bin/bash
(to exit the container without stopping it: CTRL+P CTRL+Q)
Notice the command prompt changes:
Good, we’re inside the container now!
A container lives as long it is running the process used to start it, in this case “/bin/bash”.
If you type “exit” now the container would be killed.
To leave the container without closing it type
Useful docker commands
List available images:
List all running containers:
Kill a container:
docker kill CONTAINER_ID
Connect to a container:
docker attach CONTAINER_ID
More commands in the Docker User Guide.
In the next post I’ll show you some more advanced Docker configurations and how to add software to a Docker image. Stay tuned!