if you can access to console: ALT+SysRq + s for sync, ALT+SysRq + u for remount all mounted fs in ro and ALT+SysRq+b for reset. or, if your system is xen domU: /usr/sbin/xm sysrq domU s, /usr/sbin/xm sysrq domU u, /usr/sbin/xm sysrq domU b Alexander