Wiping and shutting down a headless linux server over SSH.
Copies zeros over the whole disk.
dd if=/dev/zero of=/dev/sdaX
Where sdaX is the device you want to wipe. Read discussion at security.stackexchange.
Since the shutdown command will be trashed by the wiping, we need to force shutdown in another way.
echo 1 > /proc/sys/kernel/sysrq
echo o > /proc/sysrq-trigger
Don’t try this at home.