What happens when you press Ctrl-Alt-Del is defined in /etc/inittab as stated eariler.
By default it is:
Code:
# What to do at the "Three Finger Salute".
ca::ctrlaltdel:/sbin/shutdown -r now
if you want it to shutdown instead you would change that to:
Code:
# What to do at the "Three Finger Salute".
ca::ctrlaltdel:/sbin/shutdown -h now
The settings are applied next reboot.