F26: Dell XPS 15 hangs on reboot and shutdown

F26_Dell_XPS_15_hangs_on_reboot_adn_shutdown.txt

My Dell XPS 15 (9560) would hang whenever I tried reboot or shutdown under Fedora 26.

The soltion I found was to add the following boot parameter.  I believe it blacklists the nouveau video driver.

  nouveau.runpm=0
  
Of course the proper place to update /boot/grub2/grub.conf is to update /etc/default/grub as such:

  GRUB_TIMEOUT=5
  GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
  GRUB_DEFAULT=saved
  GRUB_DISABLE_SUBMENU=true
  GRUB_TERMINAL_OUTPUT="console"
  GRUB_CMDLINE_LINUX="rhgb quiet nouveau.runpm=0"
  GRUB_DISABLE_RECOVERY="true"
  
Don't forget to generate a new /boot/grub2/grub.conf using this command:

  sudo grub2-mkconfig -o /boot/grub2/grub.cfg
  
A reboot (hard power off is probably needed) will fix the issue of hanging during reboot or shutdown.