9.10. Adjust behaviour of Ctrl - Alt - Delete

The IBM PC used Ctrl - Alt - Delete to launch a reboot of the computer. Linux traps this key chord and makes it available to the init system. This is done by sending the init process a SIGINT signal (although ctrlaltdel hard can undo this trap and make the key chord reboot the comptuer immediately). The init system uses /etc/inittab to determine how to handle the signal generated by the Ctrl - Alt - Delete key chord.

Most distributions cleanly reboot the system, mimicing the behaviour that most users expect. Figure 9-14 shows how this is done.

Figure 9-14. Default handling of Ctrl - Alt - Delete in /etc/inittab

# Trap CTRL-ALT-DELETE
ca::ctrlaltdel:/sbin/shutdown -t3 -r now

Depending upon each individual site you may wish to disable Ctrl - Alt - Delete . This is shown in Figure 9-15 .

Figure 9-15. Ignoring Ctrl - Alt - Delete in /etc/inittab

# Trap CTRL-ALT-DELETE and do nothing
ca::ctrlaltdel:

Alternatively, you may wish to cleanly shut down the computer. This is very easy to explain to operators and instructions can be displayed on the monitor using /etc/issue or a Post-it Note . If the computer uses Advanced Power Management (or APM ) then shutting down the computer will also remove the power.

Figure 9-16. Shut down cleanly upon Ctrl - Alt - Delete in /etc/inittab

# Trap CTRL-ALT-DELETE and shut down
ca::ctrlaltdel:/sbin/shutdown -t3 -h now