Sometimes, reboot or shutdown -r now, don’t work anymore.
That really sucks, especially if you have no access to the server room or you just don’t want to get up.
But there is another solution if your Kernel is compiled with CONFIG_MAGIC_SYSRQ (sysrq-trigger).
If so, you have the possibility so send binding command.
Reset your server (like pressing the hardware RESET button):
# echo b > /proc/sysrq-trigger
But, it might be a good idea to sync the hard disks before:
# echo s > /proc/sysrq-trigger