sysrq key is a very useful feature that can unmount the disks and reboot the machine during system freezes. It is already compiled into the kernel but I don't know why it is explicitly disabled by default in /etc/sysctl.conf. This feature is extremely useful since it prevents possible filesystem corruptions and it is very unlikely that there is any hotkey conflicts.(And pressing the sysrq key combinations by accidents is almost impossible since these keys are so far apart.) Please bring this feature back. Thanks.