Change hostname command?

Hi all, I need your help with change the hostname. When I have input in the command line 'hostname', it will display like this: # hostname server Do you know how I can change the hostname to make it to show 'server.mydomain.com'? I have already set the hostname in the WHM > Network Setup > Change Hostname. But this one is a bit different so I want to see if it is possible to change it. Thanks in advance! anyone?????????