shutdown can be called from init(8) when the magic keys CTRL-ALT-DEL
are pressed, by creating an appropriate entry in /etc/inittab.
means that everyone who has physical access to the console keyboard can
shut the system down. To prevent this, shutdown can check to see if an
authorized user is logged in on one of the virtual consoles. Otherwise it will write the message
shutdown: no authorized users logged in to the (physical) system console.
If shutdown is called with the -a argument (add this to the
invocation of shutdown in /etc/inittab), it checks to see if the file
/etc/shutdown.allow is present. It then compares the login names in that
file with the list of people that are logged in on a virtual console (from
/var/run/utmp). Only if one of those authorized users or root is logged
in, it will proceed.
The format of /etc/shutdown.allow is
one user name per line. Empty lines and comment lines (prefixed by a #)
are allowed. Currently there is a limit of 32 users in this file.
Note that if /etc/shutdown.allow is not present, the -a argument is
This is from the 'shutdown' man page, it says that you can set up a file that will keep the command limited to some users but not others. You could create the 'shutdown.allow' file with the users you will want to be able to shutdown, then create an alias named 'halt', or some other name, with the "shutdown -a" as the command to be aliased. I hope this helps.