Disable the Ctrl-Alt-Delete shutdown keys in Linux

On a production system it is recommended that you disable the [Ctrl]-[Alt]-[Delete] shutdown. It is configured using /etc/inittab (used by sysv-compatible init process) file. The inittab file describes which processes are started at bootup and during normal operation. You need to open this file and remove (or comment it) ctrlaltdel entry.
Ctrlaltdel specifies the process that will be executed when init receives the SIGINT signal. SIGINT is the symbolic name for the signal thrown by computer programs when a user wishes to interrupt the process, for example reboot/shutdown system using [Ctrl]-[Alt]-[Del].). This means that someone on the system console has pressed the CTRL-ALT-DEL key combination. Typically one wants to execute some sort of shutdown either to get into single-user level or to reboot the machine.

Disable CTRL+ALT+Del keys
Open /etc/inittab file, enter:
# vi /etc/inittab
Search for line that read as follows:
ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now
And remove the line or comment out the above line by putting a hash mark (#) in front of it:
# ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now
Save the file and exit to shell promot. Reboot system to take effect or type command:
# init q