Обновление через терминал с LinuxMint 18.3 до 19.3 --Сколько места на диске?

А как насчет xtrlock?

xtrlock locks the X server till the user enters their password at the keyboard.

While xtrlock is running, the mouse and keyboard are grabbed and the mouse cursor becomes a padlock. Output displayed by X programs, and windows put up by new X clients, continue to be visible, and any new output is displayed normally.

The mouse and keyboard are returned when the user types their password, followed by Enter or Newline. If an incorrect password is entered the bell is sounded. Pressing Backspace or Delete erases one character of a password partially typed; pressing Escape or Clear clears anything that has been entered.

If too many attempts are made in too short a time further keystrokes generate bells and are otherwise ignored until a timeout has expired.

The X server screen saver continues to operate normally; if it comes into operation the display may be restored by the usual means of touching a key (Shift, for example) or the mouse.

В моей системе Debian он находится в репозиториях:

sudo aptitude install xtrlock