# What to do when CTRL-ALT-DEL is pressed.ca:012345:ctrlaltdel:/sbin/shutdown -t3 -r now
ACCESS CONTROL shutdown can be called from init(8) when the magic keys CTRL-ALT-DEL are pressed, by creating an appropriate entry in /etc/inittab. This means that everyone who has physical access to the console keyboard can shut the system down. To prevent this, shutdown can check to see if an authorized user is logged in on one of the virtual consoles. If shutdown is called with the -a argument (add this to the invocation of shutdown in /etc/inittab), it checks to see if the file /etc/shutdown.allow is present. It then compares the login names in that file with the list of people that are logged in on a virtual console (from /var/run/utmp). Only if one of those authorized users or root is logged in, it will proceed. Otherwise it will write the message shutdown: no authorized users logged in to the (physical) system console. The format of /etc/shutdown.allow is one user name per line. Empty lines and com- ment lines (prefixed by a #) are allowed. Currently there is a limit of 32 users in this file. Note that if /etc/shutdown.allow is not present, the -a argument is ignored.
# Action on special keypress (ALT-UpArrow).kb::kbrequest:/bin/echo "Keyboard Request -- edit /etc/inittab to let this work."
alt keycode 103 = KeyboardSignal