Press ALT+SYSRQ+H and check what is printed at the hardware node console, for example:
SysRq: unRaw Boot Sync Unmount showPc showTasks showMem loglevel0-8 tErm kIll \
killalL Calls Oops
This output shows you what ALT+SYSRQ sequences you may use for performing this or that command. The capital letters in the command names identify the sequence. Thus, if there are any troubles with the machine and you’re about to reboot it, please use the following key sequences before pressing the Power button:
- ALT+SYSRQ+M to dump memory info
- ALT+SYSRQ+P to dump processes states
- ALT+SYSRQ+S to sync disks
- ALT+SYSRQ+U to unmount filesystems
- ALT+SYSRQ+L to kill all processes
- ALT+SYSRQ+U try to unmount once again
- ALT+SYSRQ+B to reboot
If the server is not rebooted after that, you can press the Power button.
