Crontab setup for shutdown at midnight

30 23 * * * /sbin/shutdown -h +31 "Shutting down at 0:01"
59 23 * * * echo "Cron shutdown scheduled in 2 minutes" > /usr/bin/wall


Shutdown every day at midnight. With sysinit, it must be "+31", not "31", otherwise it is taken to be an hour. Full path is required to shutdown utility.
sysinit shutdown only issues warnings at 30 and 15 minutes; there will be no further warning. Therefor also do a wall about 2 minutes before shutdown