I have Ubuntu MATE 16.04.6 LTS installed on a system with two monitors.
They act normally when I login to default MATE 1.12.1 session.

But the LightDM login screen looks weird on both screens:

  1. 1600x900 normal landscape (no rotation)

    1600x900 landscape

  2. 1280x1024 left portrait rotation


Details about lightdm:

$ dpkg -l | grep -i lightdm
ii  liblightdm-gobject-1-0:amd64   1.18.3-0ubuntu1.1  amd64  LightDM GObject client library
ii  lightdm                        1.18.3-0ubuntu1.1  amd64  Display Manager
ii  lightdm-gtk-greeter            2.0.1-2ubuntu4     amd64  simple display manager (GTK+ greeter)
ii  lightdm-gtk-greeter-settings   1.2.1-0ubuntu1     all    settings editor for the LightDM GTK+ Greeter
ii  ubuntu-mate-lightdm-theme      16.04.7            all    LightDM theme and default configuration for Ubuntu MATE

$ cat .dmrc 

Details from /etc/default/grub.cfg:

$ cat /etc/default/grub | grep LINUX_DEFAULT

I see this on every boot-up and currently I enter my password blindly.

How and where should I fix this problem?

Update 1: passing nomodeset in GRUB fixes LightDM login, but disables screen rotation of right monitor.

Update 2: temporary fixed by installing kylin-greeter ("The greeter for the Kylin desktop fork from unity-greeter."), but still need solution for original problem with LightDM and unity-greeter.


For screen rotation restoration; Try this...

For the initial text console?

Check: http://askubuntu.com/questions/237963/how-do-i-rotate-my-display-when-not-using-an-x-server

... and/or check the content of /etc/default/grub and make sure it contains something similar to

GRUB_CMDLINE_LINUX_DEFAULT="noplymouth video=efifb fbcon=rotate:3"

then do

$ sudo update-grub

This should make all after the grub menus/screens be rotated accordingly.

For X?
Arrange your screens with the "System Settings" > "Displays"
Then make sure that /var/lib/lightdm/.config/monitors.xml is lightdm-owned copy of $HOME/.config/monitors.xml. Take into use: reboot to see the effect.

| improve this answer | |
  • Both solutions does not work. GRUB one rotates both screens, LightDM config is not applied even if I copy it manually with sudo cp $HOME/.config/monitors.xml /var/lib/lightdm/.config/monitors.xml; sudo chown -R lightdm: /var/lib/lightdm. – N0rbert Mar 12 '19 at 17:35
  • You should have instances saying other than "normal" in the output from grep on both files, as in: sudo grep rotation /var/lib/lightdm/.config/monitors.xml .config/monitors.xml - if you do have it, then I have no more clues. – Hannu Mar 17 '19 at 20:04
  • BTW, do: sudo chown -R lightdm:lightdm /var/lib/lightdm to ensure the group is set too ! – Hannu Mar 17 '19 at 20:06

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