I got the situation, when my remote server was not able to reboot or shutdown (well.. reboot with option -f does not help sometimes). In this case we should be prepared for “emergency reboot” (this is pretty much the same as pressing the reset button on the server).
Preparation steps - we should stop all unnecessary daemons (services), unmount unnecessary disks and flush the data to disks.
So, time for “magic commands”:
echo 1 > /proc/sys/kernel/sysrq echo s > /proc/sysrq-trigger echo u > /proc/sysrq-trigger echo b > /proc/sysrq-trigger