-on the terminals of all users logged in. Five minutes before
-shutdown, or immediately if shutdown is in less than 5 minutes,
-logins are disabled by creating
-.Pa /var/run/nologin
-and copying the
-warning message there. If this file exists when a user attempts to
-log in,
-.Xr login 1
-prints its contents and exits. The file is
-removed just before
-.Nm
-exits.