This post configures automatic screen locking on power button press for i3 window manager on Linux. Here’s how:
/etc/systemd/logind.conf listens for power press events, and then produces the configured messages on dbus.
We would add HandlePowerKey=lock to this file. Rebooting the logind service kills the current login session too, so be careful.
Then install xss-lock. It is a utility that can hear for different power-related messages on dbus, and then do what we ask it to do when those messages are heard.
Add the following to ~/.config/i3/confg:
$ exec --no-startup-id xss-lock --transfer-sleep-lock -- i3lock -f --color=181a1b --nofork