Login Loop:

• Analysis: something must have failed to start, figure out what journalctl -b on a shell (ctrl-alt-f3 or f2 or f1 from user login screen)

• To temporarily refrain from touching display drivers nomodeset can be tried (boot screen click e, after quiet splash on the line starting with linux) (another option: nouveau.modeset=0)

• Display managers(?): gdm3 (configured underneath: X11, lightdm, sddm), nouveau

  • switching may help but probably won't if it is not trivial (don't even try twice)
  • xauthority files only matter when you use a specific display manager...

• Kernels that give trouble: nvidia kernels & drivers

• If you didn't find the solution to your problem, make your google search phrase more specific

• 'Solutions' (bunch of packages that were probably intended to solve all all the issues) probably prepared by professionals sudo ubuntu-drivers autoinstall (information: sudo ubuntu-drivers devices) (sudo dpkg-reconfigure gdm3) [xorg driver] sudo apt-get install xserver-xorg xserver-xorg.core xserver-xorg-video-nouveau libgl1-mesa-glx ubuntu-drivers-common

X11 commands X -configure /var/log/Xorg.0.log (these also show when checking out journalctl)

• Config files/paths (do not try down the list) /etc/modprob.d/blacklist.conf
• people like to add blacklist nouveau to this file /etc/modprobe.d/blacklist-nvidia-nouveau.conf

blacklist nouveau blacklist lbm-nouveau options nouveau modeset=0 alias nouveau off alias lbm-nouveau off

-people also like to scrutinize gdm and force it to use X11 instead of wayland /etc/gdm3/custom.conf

WaylandEnable=false

$HOME/.Xauthority/ (lightgm config; look at permissions too) $HOME/.xsession-errors /etc/X11/xorg.conf (https://bbs.archlinux.org/viewtopic.php?id=208252) /usr/share/X11/xorg.conf.d/

other logs kernel: dmesg /var/log/boot.log --- System boot log(askubuntu91286) /var/log/dmesg --- print or control the kernel ring buffer

Don't even use/not using sudo dpkg-reconfigure sddm

Other parties involved in this process (without verification) gnome-shell, glx, KMS ('enabled, then wayland works'), Xorg xrandr

Default Drivers sudo add-apt-repository ppa:graphics-drivers/ppa sudo apt update sudo apt install nvidia-367

Updater update-initramfs -u sudo update-grub (apparently updates grub config the one edited using e)

Login manager sudo apt install --reinstall gdm3 ubuntu-desktop gnome-shell sudo systemctl reboot

• check secure-boot('usually it blocks unsigned gfx driver from loading to kernel')

Make sure the packages you download are updated sudo apt-get upgrade (askubuntu1224820)

Ways to break linux (ubuntu):

• build a kernel using a different GCC version than the target (operating) system is going to use
• change python versions so packages built using system's python breaks