This rather unfortunate hanging event was caused by my neglecting to modify the firefox settings in my Debian, as outlined in the post
Debian Bullseye, KDE hangs - where to look for errors?
So, my own fault, but how do I get out of it.
A reboot does not work, not even a cold boot. I get a window system with an app menu and nothing else… blank screen and cant start a terminal.
So, boot it in recovery mode, login as root, and try to redo the upgrade, but
apt-get update says it cant find deb.debian.org
apt-get update says that I have to first do
dpkg --configure -a
because dpkg was interrupted
So I do that , and it says
pcre2-utils is in an inconsistent state, and I should reinstall it
so
apt-get purge pcre2-utils
apt-get install pcre2-utils
then run
apt-get check
and it says everything is OK.
then
sync
sync
halt
and when it stops ends with the message
`nouveau -0000:01:00.0 DRM: GPU: lockup - switching to software fbcon’
So it looks like that is what the firefox hangup was about.
On reboot, it now starts OK, and I have my Gnome window system back. Phew.
First thing I do is go into firefox and change those settings
- Use recommended performance settings OFF
- Use hardware acceleration when available OFF
Then I try another
apt-get update
apt-get upgrade
and everything is fine.
Lesson learnt… when you find out something useful , like those firefox settings, change it in ALL distros, not just the one you happen to be using at the time.a And I have to change it in Waterfox and Thunderbird as well as Firefox.