Linux driver

*OS is Ubuntu 16.04
*Arduino Uno
*Running as root
*This Uno board ran on a Windows system a couple of years ago but has been unused since

When I attempt to select a port from the tools menu, the only choice available is /dev/ttyACMO. Examination of the /dev directory shows there is no /dev/ttyACMO or other drivers as referred to in the Arduino Troubleshooting Section. Inquires at Ubuntu/Linux sites only get "inappropriate question, go away."

Any information on where I can get the correct driver, as well as any insights on making it work, would be greatly appreciated.

Thanks in advance.

If you unplug your Uno from the computer and then close and reopen the Tools menu (the Port doesn't update while the Tools menu is open), does the /dev/ttyACMO port disappear?