ScreenLock

A small Ubuntu/GNOME utility that watches for the screen locking and automatically suspends the machine 5 minutes later — but only if it's still locked when the timer runs out. Useful for laptops/desktops that are set to never dim/sleep on their own but should still suspend after being left locked and unattended for a while.

How it works

• bin/lock-suspend-timer.sh runs as a systemd user service. It uses dbus-monitor to watch the session bus for the GNOME screensaver's ActiveChanged signal (org.gnome.ScreenSaver).
• When a lock event (boolean true) is seen, it starts a 300-second countdown in the background and keeps watching for further signals. A relock partway through cancels the in-flight countdown and starts a fresh 300s timer; an unlock (boolean false) cancels it outright, so rapid lock/unlock cycles are always tracked correctly instead of the outcome depending on whichever countdown happened to start first.
• When a countdown runs to completion, it re-checks the current lock state via loginctl show-session --property=LockedHint rather than trusting the original event. If the session is still locked, it runs systemctl suspend. If you unlocked before the timer ran out, it does nothing and goes back to watching for the next lock.
• As a fallback for a dropped or delayed ActiveChanged broadcast (seen in practice during a gnome-shell stall), the script also reconciles state after every 60 seconds of D-Bus silence: it compares the actual LockedHint against whether a countdown is currently running and starts or cancels one to match if they disagree, instead of trusting the signal alone.
• systemd/lock-suspend.service is the user-level systemd unit that keeps the script running (auto-restarts on crash) and ties its lifecycle to your graphical session.
• desktop/restart-screenlock.desktop is an app-launcher icon that restarts the service on demand (handy after editing the script, or if it ever gets stuck).

Requirements

• Ubuntu with a GNOME (or GNOME-compatible) desktop session — the script depends on the org.gnome.ScreenSaver D-Bus interface, which is not present on non-GNOME sessions (e.g. plain Xfce, i3) without a compatible screensaver service.
• dbus-monitor, loginctl, and systemctl available on PATH (present by default on stock Ubuntu). The script checks for these at startup and exits with a clear error if any are missing.

Power management settings

This does not require any GNOME power settings to be changed — it just listens for the lock signal and layers on top of whatever's already configured. The one real prerequisite is that locking still has to happen somehow (manual Super+L, or GNOME's own idle-triggered auto-lock); if lock is fully disabled and you never lock manually either, there's never an event for the script to react to.

That said, most stock Ubuntu/GNOME installs also ship GNOME's own idle-based Automatic Suspend (Settings → Power → Automatic Suspend, i.e. org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type / sleep-inactive-battery-type) turned on by default. That's a second, independent suspend trigger — harmless to run alongside this script (systemctl suspend is idempotent, so there's no conflict), but since GNOME's timer counts from the start of overall inactivity while this script counts from the lock event, this script's timer usually fires first once locked, so the machine may end up suspending sooner than GNOME's own power settings suggest.

If you want this script's "suspend 5 minutes after lock" rule to be the actual, predictable suspend policy rather than a redundant second timer, turn off GNOME's Automatic Suspend (or set sleep-inactive-ac-type/sleep-inactive-battery-type to nothing) so this is the only thing putting the machine to sleep. Screen blanking (idle-delay) is unaffected either way — auto-lock-on-idle fires the same signal as a manual lock, so it works identically regardless of that setting.

Install

./install.sh

This symlinks bin/lock-suspend-timer.sh, systemd/lock-suspend.service, and desktop/restart-screenlock.desktop into ~/.local/bin, ~/.config/systemd/user, and ~/.local/share/applications respectively (backing up any existing non-symlink file first), then reloads and (re)starts the service. Safe to re-run any time.

Because the installed files are symlinks into this clone rather than copies, there's nothing to keep in sync by hand — see Update below.

Update

./update.sh

Runs git pull and then install.sh again — the equivalent of apt update && apt full-upgrade for this repo. Since install uses symlinks, there's no copying involved; this just pulls the latest code and restarts the service so it picks it up.

Verify it's running

systemctl --user status lock-suspend.service
journalctl --user -u lock-suspend.service -f

Lock your screen and watch the journal — you should see "Lock screen detected!" immediately, and either a suspend or an "Aborting suspend" message ~5 minutes later depending on whether you unlocked in time.

Uninstall

systemctl --user disable --now lock-suspend.service
rm ~/.config/systemd/user/lock-suspend.service
rm ~/.local/bin/lock-suspend-timer.sh
rm ~/.local/share/applications/restart-screenlock.desktop
systemctl --user daemon-reload

(These are symlinks if installed via install.sh, so rm just removes the link — the repo clone itself is untouched.)