Official Red Hat Linux Administrators Guide

By default, /etc/inittab specifies that your system is set to shut down and reboot the system in response to a Ctrl-Alt-Del key combination used at the console. If you would like to completely disable this ability, you will need to comment out the following line in /etc/inittab by putting a hash mark (#) in front of it:

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

Alternatively, you may just want to allow certain non-root users the right to shutdown the system from the console using Ctrl-Alt-Del. You can restrict this privilege to certain users by taking the following steps:

1. Add an -a option to the /etc/inittab line shown above, so that it reads:

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

   The -a flag tells shutdown to look for the /etc/shutdown.allow file, which you will create in the next step.

2. Create a file named shutdown.allow in /etc. The shutdown.allow file should list the usernames of any users who are allowed to shut down the system using Ctrl-Alt-Del. The format of the /etc/shutdown.allow file is a list of usernames, one per line, like the following:

   stephen jack sophie

According to this example shutdown.allow file, stephen, jack, and sophie are allowed to shut down the system from the console using Ctrl-Alt-Del. When that key combination is used, the shutdown -a in /etc/inittab checks to see if any of the users in /etc/shutdown.allow (or root) are logged in on a virtual console. If one of them is, the shutdown of the system will continue; if not, an error message will be written to the system console instead.

For more information on shutdown.allow, see the shutdown man page.