Comment 3 for bug 303601

I can also confirm this. And to repeat what I previously posted here ( http://www.reddit.com/r/linux/comments/7vry9/help_my_magic_sysrq_keys_reisub_no_longer_work_in/ ) :

Ever since I started running Ubuntu 8.10 (Intrepid Ibex), I found that the magic SysRq keys (REISUB or similar) no longer work from inside X. [It worked before, on prior versions.]

If I hit Ctrl+Alt+F1 to switch to a text mode console, the keys work fine there. (The easiest way to check is just to press AltGr+SysRq+R and it will print a message to the console.)

I can also see that the magic SysRq feature is turned on:

$ cat /proc/sys/kernel/sysrq

1

However, in the X Window environment (you typically hit Ctrl+Alt+F7 to switch back), I find that the keys do not work; when pressing AltGr+SysRq+R while having the GNOME terminal open, I can see that it just echos a registered trademark character (®).

I am using a standard Irish keyboard layout and a generic 105-key keyboard. I saw that by default the right Alt key (AltGr) was specified as a third level chooser and I first suspected that, but deactivating this didn't help. Switching to a US layout didn't appear to change anything either, except that it caused AltGr+SysRq+R to send an r instead of ®.

...

I did try the full REISUB sequence from X.

When I do that it doesn't work, and nothing gets echoed to the text mode console. However, if I happen to have a text entry box such as this one or the GNOME Terminal open while typing the REISUB sequence, I get ®éíßú when typing it using the right Alt key (AltGr). When I try the same with the left Alt key, then GNOME goes berserk and tries to take a gazillion screenshots as soon as I start holding down Alt+SysRq -- which I can recover from by going Ctrl+Alt+F1 and killall gnome-screenshot. The latter is sort of expected, as left Alt+PrintScreen is for taking screenshots of windows while the REISUB keys are supposed to work via the right Alt key (AltGr on UK and Irish keyboards). That's also how it used to work before Ubuntu 8.10. [I think.]

If I try the REISUB sequence from the text mode console it works ok.

...

...you do have an AltGr key. (...) it's the same key as the right Alt key. It's only labelled differently on on US / non-US keyboards. Whether or not you're getting the graphical characters or not depends on your keyboard layout settings, which is a software issue. But the kernel, and thus, the REISUB magic, doesn't care about that, because it always uses the same keys irrespective of higher level layout settings, because it queries the keyboard at a very low level. Which is why AltGr+SysRq+R,E,I,S,U,B. should work regardless of what's printed on the key or what your console or X keyboard layout settings are.

...

Does anyone have any ideas how to troubleshoot this? I tried googling and reading the Ubuntu forums, but all I found via that route appeared to be... even less informed.