You add a user to group docker so that you can run docker commands without having to be root or a sudoer.

On an Ubuntu 16.04 server which authenticates against AD using PBIS, I added users to group docker, but wasn’t getting recognized at all and had to use sudo, which defeats the purpose.

All I did was the following:

1. Edit /etc/group
2. go to the bottom of the file where you will find the docker group
3. change the name of the AD group from lower case to upper case characters and save, e.g.:

   docker:x:999:hobba\socrat to docker:x:999:HOBBA\socrat

4. Enjoy!