Bug#973474: gnome: Unable to log back in in after screen lock

[Simon McVittie]

On Sat, 27 Feb 2021 at 19:21:46 +0100, Marcin Owsiany wrote:
> Regarding the messages I see in syslog, see the screenshot I had attached to my
> previous message.

On a freshly-installed, up to date test VM, you should find that the gdm
login screen has a grey background, but the gnome-shell lock screen has a
dark blue background (it's a blurred version of your desktop background,
for which the default in Debian 11 is going to be dark blue). It would
be useful if you could describe the steps you use to reproduce this bug,
and at each step that involves a login screen, say whether the background
is grey or blue.

Here is a sequence of screenshots illustrating my
attempt to reproduce this, together with my system log:
<https://people.debian.org/~smcv/973474/> (and then after pressing Enter
for my test user's password, I'm back to my unlocked session, equivalent
to <https://people.debian.org/~smcv/973474/5.png>). At what point does
what you see diverge from that?

I'm surprised you see messages from Xorg: those should only appear when
you start a completely new session, not when you just lock and unlock
the screen. This suggests that maybe the session is crashing, and instead
of the gnome-shell lock screen on tty7, you are going back to the gdm
login screen on tty1.

Given that you see messages from Xorg, I would also expect to see more
messages than just those. Before locking the screen, please run

    logger "before locking"

to leave a marker in the system log; and then please look back through
the system log at least as far as that marker.

If you look at the systemd journal (as root) instead of syslog, you'll
also see "auth" messages, which could be relevant: for instance, when
you enter a wrong password, that should be logged as an "auth" message
from PAM.

Please describe the steps you took to install your test VM, including
any non-default settings used? For example, I wonder whether this is
locale-sensitive - I'm using en_GB.UTF-8 but you seem to be using a
non-English locale.

If your test VM does not contain any personal or confidential data,
and you can can transfer files off it with ssh, a shared filesystem or
paste.debian.net, it would be useful to see the entire systemd journal
(starting from boot) for this procedure:

- boot the VM
- log in as a user
- lock the screen
- unlock with a correct password

and compare it with
<https://people.debian.org/~smcv/973474/journalctl_-b.log.gz>.

Or if your test VM contains personal/confidential things, please could
you try to set up a similar VM without those and reproduce the bug there?

> Is there perhaps some setting I could tweak to convince gnome-shell to produce
> some debug output when I attempt unlocking?

Try these:

systemctl --user edit gnome-shell at x11.service
systemctl --user edit gnome-shell at wayland.service
sudo systemctl edit gdm.service

and in each case, add this:

[Service]
Environment=G_MESSAGES_DEBUG=all

Thanks,
    smcv