Tag: GDM

Linux

change background / style of GDM login screen in Ubuntu

Post author By Frank
Post date 11. May 2020

If you are using GDM3 as display manager and you want to change your background of the login screen or lock screen, you won’t unfortunately find any option in a common settings dialog. In Ubuntu you will always have the nice purple background while entering your password.

But you can change it! (Tested with Ubuntu 18.04 and gdm3 3.28.3) First you have to copy you preferred background to a system directory, for example /usr/local/share/backgrounds.

#copy background
sudo mkdir -p /usr/local/share/background
sudo cp mybackground.jpg /usr/local/share/backgrounds

Then you have to copy the current used theme of GDM3 for your modifications:

#copy current theme into local share
sudo mkdir -p /usr/local/share/themes
sudo cp /etc/alternatives/gdm3.css /usr/local/share/themes/

Then open this file in your favorite editor and search for #loclDialogGroup. You should change it to:

#lockDialogGroup {                                                                                                                                                                                                                                                                      
  background: #000000 url(file:///usr/local/share/backgrounds/mybackground.jpg);                                                                                                                                                                                                             
  background-repeat: repeat;                                                                                                                                                                                                                                                            
  background-size: cover;                                                                                                                                                                                                                                                               
  background-position: center;                                                                                                                                                                                                                                                          
}

Then you have to install your new theme using update-alternatives and check that it was successfully installed.

sudo update-alternatives --install /usr/share/gnome-shell/theme/gdm3.css gdm3.css /usr/local/share/themes/gdm3.css 100
sudo update-alternatives --config gdm3.css

Unfortunately not all components uses the gdm3.css alternative, so you additionally have to copy your css over the ubuntu provided.

sudo cp --backup /usr/local/share/themes/gdm3.css /usr/share/gnome-shell/theme/ubuntu.css

After upgrading the package gnome-shell-common, you have to look at the differences between the new ubuntu.css and your backup and patch the ubuntu.css again.

Then you should reboot to apply the changes.

Tags background, customizing, GDM, Gnome, lock screen, login screen, theme

Linux

Preventing window resizing after resume

Post author By Frank
Post date 4. May 2020

I have a laptop with high DPI display (HiDPI). I use scaling factor 100%, but login and lock screen of GDM uses 200 % because of auto detection. This is the second error concerning GDM and HiDPI displays. After unlock my system (here Manjaro) I got the following screen:

Then I had to minimize and restore the window to get a correctly rendered window.

The solution is to set the scaling factor in GDM to the same as in your user session. You can check the current setting with:

gsettings get org.gnome.desktop.interface scaling-factor

0 means auto scaling, 1 means 100%, 2 means 200% and so on.

So you can change this value from auto detection to a static value, in my case 1 for 100% scaling factor:

gsettings set org.gnome.desktop.interface scaling-factor 1

Tags DPI, GDM, HiDPI, monitor, resolution, window-size

Linux

Modify screen resolution or dpi in display manager like gdm or lightdm

Post author By Frank
Post date 4. April 2020
1 Comment on Modify screen resolution or dpi in display manager like gdm or lightdm

If you have a screen with a large resolution (for example 4k) or you have a high DPI (HiDPI) screen, you will know that the display manager uses a lower resolution or a wrong DPI setting.

The solution is very easy. As gdm or lightdm also have a normal user account with normal home directory. So you can just copy your correct monitors.xml to the home directory of your display manager. For gdm this would be:

sudo mkdir -p ~gdm/.config
sudo chown gdm:gdm ~gdm/.config
sudo cp -a  ~/.config/monitors.xml ~gdm/.config/
sudo chown gdm:gdm ~gdm/.config/monitors.xml

After reboot you will see the correct screen resolution.

This is especially useful on HiDPI changes, because GNOME Shell in Manjaro (ArchLinux) makes all windows small on screen lock, so that you have to resize them after relogin.

Tags DPI, GDM, HiDPI, LightDM, monitor, resolution, screen

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