deallocvt man page
deallocvt — deallocate unused virtual consoles
deallocvt [N ...]
The command deallocvt deallocates kernel memory and data structures for all unused virtual consoles. If one or more arguments N ... are given, only the corresponding consoles /dev/ttyN are deallocated.
A virtual console is unused if it is not the foreground console, and no process has it open for reading or writing, and no text has been selected on its screen.