Yesterday i install gdm and set it default display manager then l notice ubuntu is running but there is several lines appear on desktop when i want to shutdown system after i powered off system and start Grub Menu appear and normal boot system but nothing is appear and black screen is regularly appear even after several restart.

marked as duplicate by karel, Seth Mar 13 '14 at 0:32

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  • The questions which this is marked as a duplicate of are: 1. A very, very lengthy page about boot issues of all sorts, mainly grub problems 2. A page on how to switch back to lightdm if you've made gdm your default display manager. Neither of them answer the question, which is "why is GDM showing a black screen instead of the usual login screen". Also the only answer below is also just info on how to switch back. – Damon Smith Oct 4 '15 at 22:14

Try this:

on that black screen click Ctrl+Alt+f1

enter your user-name

password:your password

$ sudo su

enter your password


# dpkg-reconfigure gdm


# dpkg-reconfigure lightdm

and choose lightdm


(sorry for my bad English)

  • 1
    can you try to use proper formatting please? I have no idea what you're recommending. – Seth Mar 13 '14 at 0:32
  • CTRL+ALT+Fx just yields a blank black screen with a blinking cursor in the top-left, no login prompt, no response. – Jonathan Neufeld Nov 5 '15 at 6:21

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