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Disabling Shutdown Via Ctrl-Alt-Del
By default, /etc/inittab specifies that your system is set to shutdown and reboot the system in response to a [Ctrl]-[Alt]-[Del] key combination used at the console. If you'd like to completely disable this ability, you will need to comment out the following line in /etc/inittab:
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:
Add a -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'll create in the next step.
Create a file named shutdown.allow in /etc. The shutdown.allow file should list the usernames of any users who are allowed to shutdown 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:
According to this example shutdown.allow file, stephen, jack, and sophie are allowed to shutdown 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.