My Mac Mini with OSX Server had this thing that the hostname (as displayed in the Terminal app) would change after a reboot. Something that annoyed me tremendously. Thankfully there are several (Terminal) commands to change the hostname (back) to its 'original name'.

Since I wanted to change my hostname PERMANENTLY, I used the following command:

sudo scutil –set HostName new_hostname

This worked perfectly. Or so I thought.