After solving a login issue caused by an old Yubikey setup (old thread here), I remain in a situation whereby I can enter my password, click login, it throws a blank screen for a second, then shows the login prompt again. I've tried all 3 flavours in the top right corner (xfce, xubuntu, etc), no change.

I purged the nvidia drivers, lspci now says the graphics card has no active driver. I have no idea how to select the nouveau driver outside of the GUI - it's already installed, and I backed up and removed xorg.conf to prompt it to rebuild that from scratch, still nothing.

Based on this, grep nouveau /var/log/Xorg.0.log:

(II) LoadModule: "nouveau"

(II) Loading /usr/lib64/xorg/modules/drivers/nouveau_drv.so

(II) Module nouveau: vendor="X.Org Foundation"

(==) Matched nouveau as autoconfigured driver 0

(II) LoadModule: "nouveau"

(II) Loading /usr/lib64/xorg/modules/drivers/nouveau_drv.so

(II) Module nouveau: vendor="X.Org Foundation"

(II) UnloadModule: "nouveau"

(II) Unloading nouveau

(II) Failed to load module "nouveau" (already loaded, 0)

It looks like it's trying to load it twice?

lsmod | grep nouveau

Suggests it is loaded.

lspci -nnk | grep -iA2 vga

Should show which driver is in use but the result is:

"grep: vga: No such file or directory".

Completely stumped as to how to get it to use this driver.

sudo lshw -c video

Gives some interesting bits:

*-display UNCLAIMED

configuration: latency=0

I.e. no driver again, and unclaimed, whatever that means.

lspci -nnk | grep -i vga -A3 | grep 'Kernel modules'

nvidiafb, nouveau

More: this says I can bind a module (nouveau) to a device (nvidia gpu) but there's no nvidia gpu in /sys/bus/pci/drivers/.

This has various useful approaches but nothing if there's no driver loaded, other than it's not loaded (comments on answer 1). The user said "When booting via BIOS, X ends up using VESA driver, but when booting via UEFI, X cannot start at all" but IDK how they came to this conclusion.

This says you can blacklist modules but nouveau isn't blacklisted (I checked).

Any ideas? xorg.conf? I've tried backing up & deleting to no avail. Doesn't seem like anything useful in GRUB?

Grub: edit /etc/grub/default as root, remove nomodeset, save, sudo update-grub, reboot. Now using nouveau. But login loop persists...

Spoke to Unit193 in https://xubuntu.org/irc/ seems I had 2 versions of exo in my system. Purged xfce4-screensaver, then exo, then installed exo from lunar repos (sudo apt install exo/lunar), then backed up /usr/local/lib to /evillib and it's now sorted. What an ordeal!

Screensaver bug:

xfce4-session: symbol lookup error: xfce4-session: undefined symbol: xfce_screensaver_new

How to keep packages current without having to install from github:

sudo apt-add-repository ppa:xubuntu-dev/staging

Very much helped by termbin.com (cat command | nc termbin.com 9999) and ~./xsession-errors file

1 Answer 1


Solved with huge help from Unit193 in https://xubuntu.org/irc/, see answer in question.

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