How to Disable Ctrl-Alt-Delete in Ubuntu ?

Having a physical access to the keyboard can simply use the Ctrl+Alt+Delete key combination to reboot the server without having to logged on, But we can prevent the use of this key combination on a production server for an accidental reboots.

To disable the reboot action taken by pressing the Ctrl+Alt+Delete key combination,

Comment out the following line in the file /etc/init/control-alt-delete.conf

$ sudo vi /etc/init/control-alt-delete.conf

Or

$sudo gedit /etc/init/control-alt-delete.conf

Find line that read as follows:

exec shutdown -r now “Control-Alt-Delete pressed”

delete configuration line or comment out line by prefixing # symbol

#exec shutdown -r now "Control-Alt-Delete pressed"

Save and close the file.

But In 16.04

In the systemd world, Ctrl+Alt+Delete is handled by ctrl-alt-del.target

ctrl-alt-del.target systemd starts this target whenever Control+Alt+Del is pressed on the console. Usually, this should be aliased (symlinked) to reboot.target.

Disable Ctrl+Alt+Delete using following command

$systemctl mask ctrl-alt-del.target

$systemctl daemon-reload