A “Ghost printer” is shown in Cups
The printer is removed from the UMC completely, but even after removing it from cups, the printer becomes visible again.
shows the printer
lpadmin -x <printer>
removes the printer, but after restarting cups it is shown in the list again.
You should know, that a failed listener command for printers is stored in
/var/cache/univention-printserver. Each restart of cups, it looks in this directory and tries to apply its content.
Remove the content of