Disable Ctrl + ALT + Del restart

01. Login as root

02. Edit the following system file (inittab)

03. To locate the system file
#whereis inittab

04. To find out the file type
#file /etc/inittab

05. To edit the text editor
#nano /etc/inittab

06. Comment this line
#ca::ctrlaltdel:/sbin/shutdown –ts –r now

07. Save this file
Ctrl + O

08. Exit the file
Ctrl + X

09. Reload the inittab file in to memory again
#init q
or otherwise we have to restart the system