Ubuntu 15.10 upgrade gives blank screen
I did the upgrade to 15.10 and I boot up into a blank screen. I am able to get to the consoles, tty1, tty2, and etc. I do have a video card; I think it is NVIDIA...
Tried all the above and also tried upgrading (and downgrading) my nvidia drivers.
In the end what worked was to uninstall nvidia using
sudo apt-get purge nvidia
and remove nvidia files from /etc/modprobe.d/ - these were stopping nouveau from loading I also copied a backup of xorg.conf file to /etc/X11/xorg.conf then rebooting worked.
[edit] In fact this was not a complete solution since it only worked sometimes. In the end I also needed to create a folder /var/lib/lightdm (see https://askubuntu.com/a/692627/451489) and also fix my .Xauthority permissions https://askubuntu.com/a/223634/451489) - now lightdm, X and unity all appear to be working reliably.
I had the exact same problem. I had to reinstall my desktop (kubuntu) which in turn reinstalled my display manager. One or both fixed the problem for me.
sudo apt-get install kubuntu-desktop
Just replace kubuntu-desktop with your desktop of choice and then reboot.
I followed a link to "How to backup settings and list of installed packages" thatwas very helpful. I also made a copy of /etc/passwd. I did that then found after the "clean install" I did not need to restore! The "clean install" left all my packages there (except TrueCrypt disappeared). When I reestablished my link to the home directory on the RAID array, The settings were generally restored. Working well now. Thank you. I was expecting that the "clean install" would format the drive first before installing the OS, but I am pleasantly surprised to find that my expectation was incorrect! I would rather be lucky than right.
This answer https://askubuntu.com/a/692627/172035 solved it for me:
It is possible that the folder /var/lib/lightdm has not been created.
You could try: mkdir -p /var/lib/lightdm; chown -R lightdm:lightdm /var/lib/lightdm ; chmod 0750 /var/lib/lightdm with root permission if needed.