Hi all, I've been having fun today trying to get the Magic Sysrq key to work on my Ubuntu 10.04 system (most recent kernel .config was for 2.6.37-rc7). I noticed it wasn't working by accident when I tried to use it (which presumably means I haven't used it since I was using Gentoo - ouch, a while ago.) This is probably not strictly a kernel issue - I apologise if you think it doesn't belong here, but I thought I'd share my adventure with the list in case anyone else had this problem and looks for help here. I always build the Sysrq into the kernel so I went back to check that my .config was right - sure enough, CONFIG_MAGIC_SYSRQ was set to "y". Documentation/sysrq.txt states: *'When running a kernel with SysRq compiled in, /proc/sys/kernel/sysrq controls the functions allowed to be invoked via the SysRq key. By default the file contains 1 which means that every possible SysRq request is allowed (in older versions SysRq was disabled by default, and you were required to specifically enable it at run-time but this is not the case any more).'* Hmm, not on my machine: *julie@zeus:/proc/sys/kernel$ cat sysrq 0* After a considerable amount of faffing about and searching I managed to find the solution, which is to find the sysctl.conf file (*/etc/sysctl.conf*) and add the following line: *kernel.sysrq = 1* The system now boots with the Magic Sysrq key enabled by default. Note that trying to sudo echo a value into /proc/sys/kernel/sysrq doesn't work: *julie@zeus:/proc/sys/kernel$ cat sysrq 0 julie@zeus:/proc/sys/kernel$ sudo echo "1" > sysrq bash: sysrq: Permission denied julie@zeus:/proc/sys/kernel$ ls -l sysrq -rw-r--r-- 1 root root 0 2010-12-29 19:37 sysrq * Instead, I have to explicitly log in as root: *julie@zeus:/proc/sys/kernel$ cat sysrq 0 julie@zeus:/proc/sys/kernel$ su Password: root@zeus:/proc/sys/kernel# echo "1" > sysrq root@zeus:/proc/sys/kernel# exit exit julie@zeus:/proc/sys/kernel$ cat sysrq 1* or sudo a shell: *julie@zeus:/proc/sys/kernel$ sudo bash [sudo] password for julie: root@zeus:/proc/sys/kernel# echo "1" > sysrq root@zeus:/proc/sys/kernel# exit exit julie@zeus:/proc/sys/kernel$ cat sysrq 1* Which I presume might be counter-intuitive for some Ubuntu users, as AFAICR they're not encouraged to create an explicit root account but are expected to sudo everything instead - in other words they're likely to simply tag 'sudo' in front of any CL operation that would normally be root-only and expect it to work. ............................................. I don't know enough about things that are outside the kernel tree to know whether the /proc/sysrq configuration default is a distro thing or whether it's resulted from the recent kernel discussions about restricting access for security reasons to files/settings exposed by /proc. Does anyone know this or might anyone point me to the corresponding discussion? Thanks Julie