Session lock

From ArchWiki

There are numerous utilities to lock the screen of a session. But it is important to note that the utility to use is highly dependent on the environment you are in, either the virtual console, or a specific display server (Xorg or Wayland).

See List of applications/Security#Screen lockers.

By environment

This article or section is a candidate for merging with List of applications/Security#Screen lockers.

Notes: Same purpose, only split into categories. (Discuss in Talk:Session lock)

Virtual console

You can use vlock or physlock to lock a virtual console.

Xorg

There are many ways to lock the session under Xorg, so this section is likely to be incomplete. Some methods however include:

Most desktop environments come with some way to lock the session.

Wayland

You can lock the session with one of the following methods:

Triggering the lock

You can lock a session using different methods:

  • from a terminal
  • using a GUI:
    • from a desktop icon
    • using hot corners
    • from a menu (mouse or keyboard driven)
  • from a shortcut
  • from an event:

The last point (triggering a lock from an event) is the trickiest, because you can do it in one of two ways:

  • get the action trigger to execute your lock, then to execute the initial action.
  • from the event trigger, add the lock to the event chain. So far this can only be done using systemd.

Shell triggers

Zsh

To execute a command after terminal inactivity, you can use the TMOUT environment variable.

You can combine it with a trap on the ALARM signal to execute the lock. Without a trap, it will just terminate the shell.

You might want to detect if you are in a graphical environment, otherwise your GUI terminals might start disappearing without you understanding why.

Xorg triggers

xss-lock

xss-lock is triggered by one of two things:

  • systemd events
  • DPMS

The advantage of this is that you can control a lock issued manually, by inactivity, and by a suspend command at the same place.

To execute an action on one of those events: 

$ xss-lock locker-utility
systemd events

By default, xss-lock subscribes to suspend, hibernate, lock-session, and unlock-session with appropriate actions (run locker and wait for user to unlock or kill locker).

You can prevent xss-lock from being triggered by suspend and hibernate using --ignore-sleep.

You can trigger a manual lock using loginctl lock-session, or lock all current sessions with loginctl lock-sessions.

DPMS

To configure DPMS signaling timeout: 

# Trigger screensaver after 10 minutes of inactivity
xset s on
xset s 600

DPMS signaling can also be configured in /etc/X11/xorg.conf.d/ in the Monitor section.

Using DPMS signaling, you can set a second timer, for example to notify the user or to dim the screen. For example (from xss-lock(1)): 

# Dim the screen after three minutes of inactivity, lock the screen two minutes later using i3lock:
xset s 180 120
xss-lock -n dim-screen.sh -- i3lock -n

An example dim-screen.sh script can be found in /usr/share/doc/xss-lock.

Note: When using xss-lock with DPMS, you will have to blank the screen yourself. It will not be triggered when looking at videos.

xautolock

Install the xautolock package. 

$ xautolock -time 12 -locker "systemctl suspend" -detectsleep
Note: xautolock has restrictive timer limits:
  • 1 min to 1 hour for time
  • 10 min to 2 hour for killtime
It might be necessary to add -detectsleep to prevent xautolock from locking the session after resuming. One nice feature of xautolock is the corners.

Wayland triggers

swayidle

swayidle listens for idle activity from the Wayland compositor, as well as systemd events, and executes commands accordingly. See Sway#Idle.

hypridle

hypridle Hyprland's idle daemon. See upstream for configuration.

D-Bus notification

Using loginctl lock-session, or the lock action in logind.conf(5), you can notify the system through DBUS that you want to lock. This notification can then be processed, for example by xss-lock.

Inactivity

In logind.conf(5), you can configure the IdleAction to lock. This will trigger a DBUS notification, that will have to be processed (for example by xsslock) to lock the session.

Note that this is for a global system (so this is not ideal for a multi user environment).

Note also that "this requires that user sessions correctly report the idle status to the system".

Units

Before suspend or hibernate

You can use a Sleep hook. 

[Unit]
Description=Lock the screen
Before=sleep.target

[Service]
User=%I
Type=forking
Environment=DISPLAY=:0
ExecStart=/usr/bin/i3lock -c 000000

[Install]
WantedBy=sleep.target

To enable it for a certain user, enable sleep@Username.service.

Lid closing

You can use the lock action using the related ACPI event.

See also