In previous Debian releases I would simply comment out the line controlling Ctrl-Alt-Del key presses in the /etc/inittab file, and this would prevent any action from occurring due to pressing those keys. As an example, here is what I had in the inittab file in Wheezy:
# What to do when CTRL-ALT-DEL is pressed.
#ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now
In Jessie, this is proving to be more challenging as there is no inittab file to edit, and while I could create one, it would only contain commented lines, having a null effect. It seems that in prior releases, one had to explicitly say what to do in order for anything to happen, and in Jessie, one has to explicitly say "do nothing" or action is taken (the logout/reboot/shutdown prompt is presented with a 30 second timeout).
I have seen discussions of manipulating the symbolic link file /etc/systemd/system/control-alt-del.target which points to reboot.target in the same directory. For example, it's been said that linking it to shutdown.target would cause a shutdown action instead of a reboot action. I haven't tried that, but I have tried pointing the link to /dev/null and followed the change with 'systemctl daemon-reload', however it had no effect - I still get the logout/reboot/shutdown prompt in response to pressing Ctrl-Alt-Del.
Per another thread, I have also tried creating /etc/init/ctrl-alt-del.conf containing only the single comment line '# do nothing when Ctrl-Alt-Del is pressed', yet this has no effect either - the prompt still appears.
So I'm at a loss for the moment. Please advise if you know how to completely disable Ctrl-Alt-Del in Jessie - I want the key press to be ignored, just like it was in Wheezy I commented out the line in inittab shown above. Thanks.