Fwd: Is disabling ctrl-alt-backspace really such a good idea?

John Moser john.r.moser at gmail.com
Thu Feb 12 06:36:43 UTC 2009

Thomas Jaeger wrote:
> John Moser wrote:
>> On 2/12/09, Thomas Jaeger <thjaeger at gmail.com> wrote:
>>>> Things that can happen:
>>>> * Client can grab keys but hang.
>>> In that case, you get the X Server back to normal by killing the client
>>> and you should try and fix the client.
>> Killing the client actually prevents X from having any input; you lose
>> the input until you open a similar client (i.e. qemu) that regrabs,
>> then close it normally so it releases.
> This is not how grabs work.  If a client that has grabbed the
> Keyboard/Pointer/Server is killed all grabs are automatically released.

Try this when qemu freezes.  I've frequently had to C-A-F1, kill qemu, 
then alt-F7 back and ... wow, nothing works.  C-A-F1, DISPLAY=0:0 qemu, 
go back, hit a button, hit C-A to release grab, and close qemu.  Repeatably.

>>>> * Xorg/drivers can have a bug that locks the screen.
>>> As I said before, I doubt C-A-B will help you there. Shift+SysRq+K
>>> might, though.
>> Happens occasionally.  Shouldn't.  It breaks X clients' ability to
>> talk to the screen, doesn't update the screen, so everything waiting
>> on X hangs; but X still picks up the C-A-B somehow and dies.
> Bug report?
>> Computers will always do very strange thnigs, most of which don't make
>> sense and shouldn't happen.
> Those things can be fixed though.

Yes, exactly.  Just don't be surprised if someone says something happens 
that shouldn't.

More information about the Ubuntu-devel-discuss mailing list