Bug#819190:

[Luca Boccassi]

On 4 April 2016 at 00:03, Bernat Arlandis <bernat.arlandis at gmail.com> wrote:
> I was having this problem and I think it's solved now.
>
> I was using the current nvidia driver until my graphics card became
> obsolete, then I installed the legacy driver and  uninstalled the current
> driver. It was left in a broken state after that.
>
> I tried to dist-upgrade or remove the nvidia packages but it failed telling
> me to run "dpkg --configure -a". When I tried to do that the command would
> hang so I was stuck.. Examining the running processes in another console I
> could see it was the /usr/lib/nvidia/check-for-mismatching-nvidia-module
> script that hang.
>
> I edited said script putting an exit command at the start of the script so I
> could resume dpkg execution, then I purged all nvidia packages and installed
> the legacy package succesfully this time.
>
> Questions:
>  - what is your Nvidia card (lspci verbose output please)?
>
> 01:00.0 VGA compatible controller: NVIDIA Corporation G92 [GeForce 9800 GT]
> (rev a2) (prog-if 00 [VGA controller]) Subsystem: ASUSTeK Computer Inc. G92
> [GeForce 9800 GT] Flags: bus master, fast devsel, latency 0, IRQ 31 Memory
> at f6000000 (32-bit, non-prefetchable) [size=16M] Memory at c0000000
> (64-bit, prefetchable) [size=256M] Memory at f4000000 (64-bit,
> non-prefetchable) [size=32M] I/O ports at e000 [size=128] Expansion ROM at
> f7000000 [disabled] [size=128K] Capabilities: <access denied> Kernel driver
> in use: nouveau Kernel modules: nvidia
>
> (This is after succesfully removing the nvidia packages, thus the nouveau
> driver.)
>
>  - are you on stable, testing or unstable?
>
> Testing.
>
>  - if I understand correctly you have an amd64 installation. Did you add
> i368 via dpkg --add-architecture?
>
> Yes. Had nvidia i386 packages installed.
>
>  - did you ever have non-legacy-340xx packages installed?
>
> Yes. I had them until they become incompatible with my card.
>
>  - are you installing from a tty or is yours a laptop with an optimus
> system?
>
> It's a desktop system and tried from a gnome terminal and a remote ssh
> session.
>
> I hope this helps someone.

Hi,

Thanks, this is useful info. If you run
/usr/lib/nvidia/check-for-mismatching-nvidia-module manually now (with
the current version as the parameter, eg: "340.96"), does it still
hang? If so, could you please add "set -x" at the top and run again,
to see where it hangs exactly?
I will try to reproduce this myself sometimes this week, but I've
never seen it hang before, although I do not possess hardware not
supported by the current series. I'll try to hack it to make it think
I do.

In general, removing nvidia-driver is not necessary when switching to
a legacy, they are built to be able to co-exist. You can simply switch
from one to the other with "sudo update-glx --config nvidia" and
picking the one you want.

When you installed the legacy and removed the current, do you still
have the logs? Which packages exactly did you remove? Did you issue a
--purge?  There might be a log in /var/log/apt/history.log
Not all packages are duplicated between -current and -legacy, one of
the possibilities is that one of those got removed and that's what
might have caused the issue. The other possibility is that script
hanging for some reasons, which I hope we can get to the bottom of. Or
maybe something else I can't think of right now :-)

Kind regards,
Luca Boccassi