xlock

Lock screen immediately

$ xlock

$ xlock -mode [blank]

$ xlock -message "[Away from desk]"

$ xlock -nolock

$ xlock -timeout [30]

$ xlock -help

xlock [options]

xlock locks the X display until the user enters their password. While locked, the screen displays a configurable animation or pattern, and new X server connections are refused.
Multiple display modes provide visual effects during lock. The blank mode simply blacks out the screen, while others show animations like life simulation, mazes, or geometric patterns.
The tool blanks the screen, hides the mouse cursor, and requires the user's system password to unlock. All keyboard and mouse input is captured until authentication succeeds.

-mode name

Display mode (blank, life, maze, etc.).

Message to display on lock screen.

Demo mode; no password required.

Password timeout in seconds.

Echo characters when typing password.

Use first character of password prompt.

Allow X clients while locked.

Allow remote locking.

X11 screen lockers have fundamental security limitations. Consider xsecurelock for higher security needs. Settings like -allowaccess reduce security. May not prevent all bypass methods on X11.

xlock has been part of X11 utilities since the early days of the X Window System. While functional, modern alternatives like xsecurelock address various security concerns inherent to X11's architecture that traditional screen lockers cannot fully mitigate.

xscreensaver(1), xsecurelock(1), physlock(1), i3lock(1)