I have followed the docker installation doc for installing it on my machine which is a 32 bit machine running Ubuntu 12.04
The step
$ sudo apt-get in
Now, you can install with this command sudo apt install docker.io. After this, you will see lots of lines for the installation of Docker and the installer will ask you "do you want to continue?", you need to type y. Then, the installation will be finished. Now, you can check it with this command docker version. If you see just client section, you need to type sudo docker version. After this, you will see the client and server.