If you are trying to run the Java GUI from your Linux cell manager, the 'xomni' command no longer exists, because support for the Java GUI has gone away. You will need to use the Windows GUI
The system running the Windows GUI should be in the same domain as your cell manager, if not, you would need to create some firewall rules, and set a range of ports in the 'omnirc' file, but, lets jump off that bridge if we come to it