Don’t think this as a flaw to the GNU/Linux system, but can be helpful in many situations. This part plays a vital role in the security of a system. In GNU/Linux system pressing Ctrl+Alt+Del can cause a shutdwon/reboot by default. As I said this isn’t a bad configuration and most of us may be using this as a shortcut. Moreover it is pretty important if you don’t have the best physical security to the machine. Commenting out the following line/lines will disable the possibility of using the Control-Alt-Delete command to shutdown your computer.
In debian based distros
Comment out the lines in the file to look like
# control-alt-delete – emergency keypress handling
# This task is run whenever the Control-Alt-Delete key combination is
# pressed, and performs a safe reboot of the machine.
description “emergency keypress handling”
#author “Scott James Remnant <firstname.lastname@example.org>”
#start on control-alt-delete
#exec shutdown -r now “Control-Alt-Delete pressed”
In redhat based distros
Comment the following line
ca::ctrlaltdel:/sbin/shutdown -t3 -r now
to look like
#ca::ctrlaltdel:/sbin/shutdown -t3 -r now
Save the file and logout.