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Tom Furie 02-08-2010 12:01 AM

Alt+F7 fails to switch to graphical console (X server) from a text console under some conditions
 
On Sun, Feb 07, 2010 at 06:02:30PM -0500, Stephen Powell wrote:

> I have been having trouble lately with losing access to my graphical console.
> The basic symptom is that I am in the graphical console, I switch to a text
> console via Ctrl+Alt+F1, do some stuff in the text console, then when I
> attempt to switch back to the graphical console again with Alt+F7, I get
> a black screen. I can then switch back to console number 1 simply by
> using Alt+F1. I don't need to include the Ctrl key. This would normally
> indicate to me that the X server died somehow, except that "ps aux"
> still shows processes associated with the X server, such as gdm, active.
>
> I am running the GNOME desktop on a Debian "testing" system. All packages
> are from testing, none are from unstable. I can't swear to this, but
> I think my troubles began with kernel 2.6.32. One scenario that often
> causes this failure is when the little "sun" icon appears in the upper
> right corner, indicating that there are updates available. I switch
> to text console number 1 via Ctrl+Alt+F1, login as root, run "dselect
> update", "aptitude -R full-upgrade", and "aptitude clean". I then attempt
> to switch back to the graphical desktop with Alt+F7 to cleanly shut
> things down in preparation for a reboot. But I can't get there.
> Has anybody else seen or heard of this problem? I did some internet
> searches, but didn't turn up anything that looked promising.

Have you checked Alt+F8, Alt+F9, possibly even beyond? On one of my
systems, for reasons that are still unclear to me, GDM occasionally runs
somewhere between tty8-10 after I've logged in and out a few times. I
can only guess it's restarting before it's fully stopped.

Cheers,
Tom

--
Do you mean that you not only want a wrong answer, but a certain wrong answer?
-- Tobaben

Tom Furie 02-08-2010 10:26 AM

Alt+F7 fails to switch to graphical console (X server) from a text console under some conditions
 
On Sun, Feb 07, 2010 at 10:06:20PM -0500, Stephen Powell wrote:

> I must confess I never even thought to check that. The next time
> it happens, I'll give it a try. Have either of you come up with
> a consistent scenario that always reproduces the failure? I'm not
> explicitly stopping and restarting the X server or the GDM daemon.
> I'm just switching back and forth between a text console and the
> graphical console. Has either of you filed a bug report?
> The only reason I haven't asked about this before is that I was
> hoping to come up with a consistent failure scenario. There's
> nothing worse than a bug that can't be reproduced on demand.

I haven't filed a bug report because I'm not sure what to file it
against. I'm not even sure it could be called a bug, I don't have
anything in my config to tell GDM to specifically start on tty7, so it
just grabs the first available one.

You aren't restarting X or GDM, but if GDM started on tty8, because tty7
was unavailable for whatever reason, the first you would know about it
is when you tried to switch back to it from another tty.

Cheers,
Tom

--
Truth is the most valuable thing we have -- so let us economize it.
-- Mark Twain

Tom Furie 02-08-2010 03:58 PM

Alt+F7 fails to switch to graphical console (X server) from a text console under some conditions
 
On Mon, Feb 08, 2010 at 10:13:48AM -0500, Stephen Powell wrote:

> /var/log/Xorg.0.log tells you what console it started on, and the flags
> indicate that the option is supplied on the command line. For example,
>
> Markers: (--) probed, (**) from config file, (==) default setting,
> (++) from command line, (!!) notice, (II) informational,
> (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
> ...
> (++) using VT number 7
>
> The double plus sign is the marker for "from command line". So if you
> find the script that starts the X server and supplies that command line
> option, you'll be well on your way to finding the bug. The next step
> will be to find the logic that "calculates" this command line switch.
> And if you find the faulty logic you'll know which package to report a
> bug against. (i.e. which package is this script file shipped with?)
> And you'll even be able to supply a patch file with the bug report.
> I'll start looking too, but I won't have access to that machine until
> this evening. Maybe a good place to start looking would be
> /etc/init.d/gdm.

Looking at /usr/share/gdm/defaults.conf, VT7 appears to be a coded-in
default on Linux systems.

# Automatic VT allocation. Right now only works on Linux. This way we
# force
# X to use specific vts. Turn VTAllocation to false if this is causing
# problems.
#FirstVT=7
#VTAllocation=true

The commented option lines are showing their default values. It might be
worth setting VTAllocation=false (in /etc/gdm/gdm.conf, [daemon]
section) and see if that has any effect.

Hmm, from a gdm session logged in on tty7, logging out restarts X but on
tty8. Logging out of that session also restarts X, but it stays on tty8.
Restarting, or stopping and starting, gdm brings it back up still on
tty8. This behaviour doesn't seem to be altered by the VTAllocation
setting. According to Xorg.0.log, VT8 is being passed in from the
command line.

Cheers,
Tom

--
Airplanes are interesting toys but of no military value.
-- Marechal Ferdinand Foch, Professor of Strategy,
Ecole Superieure de Guerre


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