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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

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

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