I had to clone a server to another server (1:1 copy using dd+netcat) but didn't want to stay at the customer's place until the task finished. So I executed 'Start ssh; passwd' to be able to login remotely. But how to reboot the server and get rid of the CD so the harddisk system boots instead of the grml-CD without manual interaction at customer's place? Server systems usually don't move in/re-insert an ejected CD on reboot - that's nice for what we need. So all I had to do was:
eject &>/dev/null
umount -l /cdrom
eject /dev/cdrom
echo b > /proc/sysrq-trigger
