You can use SSH (Secure Shell) to access the command line on a ClearOS system.
Linux and MacOS X already have SSH clients installed by default. Open up a terminal window and type:
Change 192.168.1.1 to the IP address of your ClearOS system. Type in your system password and you will find yourself at the ClearOS command prompt.
For Windows users, you can download the free Putty SSH tool for remote shell / command line access.
For a more colorful/friendly GUI try Tunnelier. This allows you to save multiple connection profiles, which is useful if you have more than one system to administer.
After you startup the software:
You will find yourself at the ClearOS command prompt.