Comment 74 for bug 642792

On precise (fresh install):

Alt-PrtScn does a full-screen screenshot (screenshot is taken when I release Alt). My keyboard settings pane still says that Alt-Print should screenshot a single window.

I haven't run sysctl and my sysrq value seems to have defaulted to 1:

$ cat /proc/sys/kernel/sysrq
1

Except that something has modified it:

$ ls -ul /proc/sys/kernel/sysrq
-rw-r--r-- 1 root root 0 Aug 8 09:13 /proc/sys/kernel/sysrq
$ ls -l /proc/sys/kernel/sysrq
-rw-r--r-- 1 root root 0 Aug 8 09:13 /proc/sys/kernel/sysrq

(That's 3 minutes before I started writing this comment.) I haven't done any sudo commands today, but maybe one of the PrtScn key combos did it?