Prevent non root user from shutting down or restarting a redhat system

In the file /etc/X11/gdm/gdm.conf, change the line that reads:

SystemMenu=true

to

SystemMenu=false
In the file /etc/inittab, change the line that reads:

ca::ctrlaltdel:/sbin/shutdown -t3 -r now

to

ca::ctrlaltdel:echo < "message denoting prevention of reboot" >
In the directory /etc/security/console.apps/, delete the files reboot, poweroff, and halt.
Remove the file /usr/bin/poweroff.