deallocvt

deallocvt [TTY]

TTY
    The specific TTY (virtual console) to deallocate. If omitted, deallocates the current TTY.

The deallocvt command attempts to deallocate any unused virtual consoles.
Virtual consoles are logical terminals that allow users to run multiple login sessions on a single physical system. When a virtual console is no longer in use (no process has it open as controlling terminal), it remains allocated in memory. deallocvt reclaims this memory, making it available for other processes.
This is useful on systems with limited memory resources, especially when many virtual consoles have been created and then abandoned. By default, the command operates on the current TTY. Specifying a TTY with an argument limits operation to this virtual console.
It is typically run automatically as part of system shutdown scripts to free up resources before the system halts. If the command fails, a warning message is printed to standard error. Failures can occur, for example, if the virtual console is still active, or if the command does not have sufficient permissions.
deallocvt utilizes the ioctl system call VT_DISALLOCATE to achieve the deallocation. This command doesn't guarantee immediate memory release, but it signals to the kernel that the console is no longer needed and can be reclaimed when appropriate.

The deallocvt command returns 0 on success and a non-zero value on failure.

deallocvt usually requires root privileges to deallocate virtual consoles. Without root privileges, it may only be able to deallocate the current virtual console.

chvt(1), openvt(1), tty(1)