bug#36924: fixing GDM + GNOME Shell

[Mark H Weaver <mhw@netris.org>]

Hi Ricardo,

Ricardo Wurmus <rekado@elephly.net> writes:

> Today I again couldn’t log into my workstation after upgrading the
> system.  I’m using GDM + GNOME Shell.
>
> At first GDM wouldn’t start.  I knew what to do: remove /var/lib/gdm,
> because some state must have accumulated there.
>
> GDM came up after a reboot, but I still couldn’t log in.  Instead I was
> thrown back to the login screen without any error message.  I looked in
> ~/.cache/gdm/session.log for information, but it only told me that
> gnome-shell was killed.  Thanks.
>
> After removing both .local/share and .cache out of the way I could log
> in again.
>
> This happens whenever I upgrade the system.  This makes the system
> rather frustrating to use.  I don’t know if booting into an older system
> generation would result in the same problem, but my guess is that it
> would because both GDM and GNOME Shell appear to be leaving some binary
> files behind that cause different versions to crash unceremoneously.
>
> What can we do to make GDM and GNOME Shell more reliable?

It's interesting that I've never run into this problem, not even once,
in all my years of running GNOME on Guix systems.  Since recently
reverting to mostly using GNOME under X and GDM (whereas for a while I
was mostly launching GNOME manually under Wayland), I've run into some
other problems, e.g. GDM suspending my system automatically, sometimes
immediately after logging out, but I've *never* had to remove my caches.

I wonder if this is related to my use of Btrfs instead of Ext4.  Whereas
system crashes cause file system corruptions under Ext4 (usually in the
form of some files being left empty after a crash), I've never seen any
evidence of corruption from crashes under Btrfs.

       Mark