Shutdown from login prompt in tty

On most Linux systems, the Ctrl+Alt+Del key sequence action is configured in either /etc/inittab or /etc/init/control-alt-delete.conf.

Usually, this will reboot the system, but you could modify the command to halt the system instead.

In /etc/inittab:

ca::ctrlaltdel:/sbin/shutdown -t3 -h now

Or /etc/init/control-alt-delete.conf:

start on control-alt-delete    
exec /sbin/shutdown -h now "Control-Alt-Delete pressed"

I've done this before with a user named "s" and no password.

IIRC you set the user's shell to /sbin/shutdown. Prolly need to add it to /etc/shells.

Here's a nice little trick that kind of surprised me (life saver if you freeze a remote system with no iLO (or KVM). The Magic SysRq key. If it is active on your system, I believe hitting ALT + SysRq + o should turn off your system. This is a hard shutdown (if I recall correctly, don't want to test it right now!) so you can press: ALT + SysRq + e (nicely kill all processes) ALT + SysRq + i Kill everything else) ALT + SysRq + s sync all file systems, ALT + SysRq + u to remount partitions as read only, then do the b or o combination (reboot or shutdown)

Anyway, I don't think this is the best way to halt your system, the other answers may be more suitable, but the above should help you out if your stuck!