nvidia 304 and fc23: black screens after updating today

[stan]

On Tue, 11 Oct 2016 22:40:28 +0100
John Pilkington <J.Pilk at tesco.net> wrote:

> Thanks for coming back to me about this.  Because I can't access the 
> usual desktop features I'm in unfamiliar ground. The system was
> updated on 3 Oct and worked.  The update on 10 Oct caused the
> problems from which I have been trying to recover. 
> xorg-xll-drv-nvidia-304xx-304.131-3 was working; 304.132-1 did not.
> I believe there was a kernel update too.

From the other email (from Nicolas), it sounds like there might be a
problem with the nvidia driver.

> I have been through several cycles of 'dnf remove' and 'dnf install', 
> akmods-shutdown, akmods --force.  I now have a mockuser defined.  But 
> most recently the kmod builds were failing and the logs are 
> incomprehensible.

If you get into multiuser (old runlevel 3) as described below, you
should be able to log in as root and view /var/log/dnf*.log to see
exactly which updates occurred, and any messages that dnf issued about
them.
> 
> I have now removed all nvidia packages in the hope of getting a
> working system with nouveau.  There's a long thread now on
> fedora-users about that, although it has wandered off course.

I think getting nouveau working is a good idea.  It's been a while, but
I remember that there were things hiding in unlikely places that had
to be removed on this switch.  Try searching online to find recent
instructions for the best way to do this.

> Currently (KDE) plasma login with nouveau appears normal for perhaps
> 10 seconds, then collapses to a featureless screen with a mouse
> cursor that moves but seems to do nothing else.  ctrl/alt/F2 brings
> up the tty2 screen as mentioned below, which, without an active
> window, is the only way I know to access the file system;  I haven't
> yet tried an emergency boot.

I'm not sure what boot process you are using, but can you edit the menu
during boot to boot to multiuser?  If you have access to the system,
edit /boot/grub2/grub.cfg and make sure that you have set_timeout=10 or
some other number that gives you a chance to interact.  Also check that
the linux16 line has no quiet on it.  Be sure that nouveau isn't
blacklisted on that line as well.  And put a 3 on the end of the
linux16 line, so you come up in multiuser instead of graphical.  That
will give you a working system to look at the graphical setup.  Or, the
10 second pause will give you a chance to put an e on the boot line,
hit enter, and use the arrow keys to go to that line, and add the 3
temporarily.

> startx from tty2 allows login but then collapses again.  Doing it
> from tty3-ish says 'Could not start ksmserver.  Check your
> installation' which prompts unfriendly feelings but does perhaps give
> some clue about what has gone wrong.  But maybe it's because too many
> screens are being referenced.  xrandr 'Can't open display'.

Unless you are in X, xrandr isn't going to work, and it sounds like you
aren't able to bring up X.  

> the green nvidia logo appears briefly.  I don't think it should do
> that with nouveau.  But there's a multi-screen factor here (VGA and
> HDMI (TV)) and I saw it only on the HDMI.

I agree that you shouldn't see the nvidia logo flash with nouveau.
Is it easy to move to a single display?  That will remove a variable
from consideration.

Nasty problem.