A Linux Journal article about rebooting a failing box remotely using the magic sysrq key.. without needing console access. Assumes that you compiled this support into the kernel (many distros do by default while users might not).
- echo 1 > /proc/sys/kernel/sysrq
- echo b > /proc/sysrq-trigger
Optionally: echo "kernel.sysrq = 1" >> /etc/sysctl.conf