Set or Change Hostname (via the GUI)

• Open System Preferences
• Select Sharing
  Select the Edit button and enter your desired Local Hostname and click OK
  

Note:  If the Edit button is greyed out, click on the Lock Icon, authenticate with an admin account

To temporarily change the Hostname of your device via the terminal 

Set or Change Hostname (via Terminal) - OS X Mavericks or newer

• Open Terminal by going to Applications, then Utilities, and select Terminal

• The type the following:

sudo hostname -s new_hostname
For example:  sudo hostname -s ECE-MAC

To permanently change the Hostname of your device via the terminal

Set or Change Hostname (via Terminal) - OS X 10.6 - 10.8

• Open Terminal by going to Applications, then Utilities, and select Terminal

• The type the following:

sudo scutil –-set HostName new_hostname
For example: sudo scutil –-set HostName ECE-MAC

Note:  It may also be necessary to perform the following commands to solidify the changes

sudo scutil --set ComputerName <hostname>

For example:  sudo scutil --set ComputerName ECE-MAC

sudo scutil --set LocalHostName <hostname>

For example:  sudo scutil --set LocalHostName ECE-MAC