[Guide] Customize Qubes OS 4.3 Login Screen (Avatar + Dark Mode)

guides #version-r43 #configuration #dom0 #gui #theme

This is a step‑by‑step guide for changing the user avatar and enabling a dark theme on the Qubes OS 4.3 login screen (LightDM). It also explains why the lock screen behaves differently and what is (and isn’t) possible there.

If you see any errors in this guide, please inform me so I can make the necessary corrections.

[details="(IMG) Example"] Qubes|376x500 [/details]

Overview

Qubes OS 4.3 uses LightDM as the display manager for the initial login screen. That’s where you can:

When you lock your session, however, Qubes uses XScreenSaver, which works differently and has separate limitations (covered below).

All changes in this guide happen in dom0.

Prerequisites & Warnings

Change the Login Screen User Avatar

LightDM’s GTK greeter supports a default user image. You can point it to any PNG (or similar) image available in dom0.

3.1 Choose or add an image in dom0

  1. Open a terminal in dom0.
  2. Copy an existing image or add your own. Example using the Qubes logo:
# In dom0
sudo cp /usr/share/icons/hicolor/96x96/apps/qubes-logo-icon.png \
  /usr/share/pixmaps/my-user.png

sudo chmod 644 /usr/share/pixmaps/my-user.png

You can replace the source path with any image you’ve placed in dom0, but putting the final file under /usr/share/pixmaps/ is a simple, standard choice.

3.2 Copy a profile picture from an AppVM or DispVM

If your profile picture is in an AppVM or DispVM (for example, disp1234), you can copy it into dom0 with qvm-run --pass-io.

Warning: Only do this for images you fully trust. Importing files into dom0 can weaken your overall security if those files are malicious or come from untrusted sources.

  1. Make sure the picture exists in the VM, e.g. in ~/Downloads/ProfilePicture.jpg.
  2. In dom0, run:
qvm-run --pass-io disp1234 'cat /home/user/Downloads/ProfilePicture.jpg' \
  > /usr/share/pixmaps/ProfilePicture.jpg
  1. Set safe permissions in dom0:
sudo chmod 644 /usr/share/pixmaps/ProfilePicture.jpg
  1. You can now use /usr/share/pixmaps/ProfilePicture.jpg as your avatar path in the LightDM config (next section).

Again, before copying anything into dom0, be sure you trust the file and the VM it comes from. Dom0 is supposed to stay as clean and secure as possible.

3.3 Point LightDM to your custom image

  1. Edit the LightDM GTK greeter configuration in dom0:
sudo nano /etc/lightdm/lightdm-gtk-greeter.conf
  1. Find the [greeter] section. If it doesn’t exist, create it. Then add or edit (pick the filename you used above):
[greeter]
default-user-image=/usr/share/pixmaps/ProfilePicture.jpg

or, if you used the earlier example:

[greeter]
default-user-image=/usr/share/pixmaps/my-user.png

Make sure there is only one default-user-image= line in the [greeter] section.

  1. Save and exit (Ctrl+O, Enter, Ctrl+X in nano).

  2. Reboot (simplest and safest) so LightDM reloads the config:

sudo reboot

After reboot, your initial login screen should show the new avatar instead of the default icon.

Set a Dark Theme for the Login Screen

You can tell the LightDM GTK greeter to use a dark GTK theme, and you can control the background image by changing your desktop wallpaper in System Settings.

4.1 Edit the LightDM GTK greeter config (theme only)

  1. In dom0:
sudo nano /etc/lightdm/lightdm-gtk-greeter.conf
  1. Under [greeter], add or update this line (adjust theme name if you like):
[greeter]
theme-name=Adwaita-dark

Notes: - theme-name: The GTK theme. Common dark options in Xfce/Qubes include Adwaita-dark, Greybird-dark, or others you’ve installed.

  1. If the file already has a theme-name= line, either:
  2. Replace it with your value, or

  3. Comment it out with # and add your own line.

  4. Save and exit, then reboot:

sudo reboot

After reboot, the login window (the LightDM greeter) should use the dark GTK theme.

4.2 Change your desktop wallpaper (reflected on login)

The login screen background typically follows the system’s desktop background configuration. To change it through the graphical settings:

  1. In dom0, open the menu:
  2. Start (Qube Menu) → Settings (Gear/Cog Icon) → System Settings → Desktop
  3. Change your desktop wallpaper to the image or color you prefer.
  4. Apply the changes and log out or reboot.

Your new desktop wallpaper should now be reflected on the login screen background as well.

Important: Login Screen vs Lock Screen

A key point that often causes confusion:

Consequences:

Can I make the lock screen show the same user icon?

Not in any simple, supported way. To do that you would need to:

This is well outside normal configuration and would be unsupported and fragile across updates. Practically speaking, you should treat:

Troubleshooting