/lib/udev/lmt-udev is in laptop-mode-tools 1.68-3ubuntu1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 | #!/bin/sh -e
# /usr is not guaranteed to be mounted when udev starts
non_systemd_way() {
	if [ -e /lib/udev/hotplug.functions ]; then
		. /lib/udev/hotplug.functions
		wait_for_file /usr/sbin/laptop_mode
		exec /usr/sbin/laptop_mode "$@"
	else
		file=$1
		timeout=$2
		[ "$timeout" ] || timeout=120
		count=$timeout
		while [ $count != 0 ]; do
			[ -e "/usr/sbin/laptop_mode" ] && exec /usr/sbin/laptop_mode "$@" && return 0
			sleep 1
			count=$(($count - 1))
		done
		mesg "$file did not appear before the timeout!"
		exit 1
	fi
}
# Under systemd, we don't do synchronous operations, so we can run in the foreground;
# And we need also need to run in foreground, because forked children get kill immediately
# under systemd/udev
if [ -d /run/systemd/system ]; then
	exec systemctl --no-block reload-or-restart laptop-mode
else
	# Under sysvinit/upstart, we need to fork as we start the long-running
	# /usr/sbin/laptop_mode process.
	#
	# Also, if this happens during boot, we may want to wait until /usr is available
	# This else stanza is going to be used rarely, because going forward we are
	# going to use systemd.
	# But for compatibility reasons, we'll carry this
	#
	# That said, we background the execution here, because, otherwise udevd will wait
	# for this process which will block
	
	exec > /dev/null 2>dev/null
	non_systemd_way "$@" &
fi
exit 0
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