Last Review: Dec-04-2011

How to change GDM3 background within Linux Mint Debian (LMDE)

If one does'nt like the default greeting screen artworks there is an annoying problem arising every now and then when updating results in new design defaults for the GDM3 login manager (GNOME Display Manager) since changing GDM3 background is not possible via any configurations dialog.

Basically my approach is to overwrite the given background picture with my own one (after making a backup copy of the original one, named xyz_original.xyz; of course you do this as root). Until now I identified these background graphics files:

/usr/share/backgrounds/linuxmint-julia/emvalibe_silver.jpg
/usr/share/backgrounds/linuxmint-debian/gelsan_debian.png
/usr/share/images/desktop-base/login-background.svg

The latest one surprised me with being a vector image, so I transformed my personal background into an SVG file, renamed it to login-background.svg and overwrote the original file with it. While I thougt the job was done in the usual way, the result was a background picture accompanied with ugly blue stripes on both sides of my screen. Playing with the graphic's overall size produced more strange greeting screens until I realized, that GDM3 cannot stretch (zoom) SVG files as it does with pixel graphics, so if you don't match the original graphics exact size, you get weird results. Fortunately GDM3 still accepts pixelgraphics, so you can use your previous pictures.

Do the following things to change GDM3 background:

Step 1)
Delete the original background picture (This isn't really necessary, but after doing so, anyone knows for sure that login-background.svg is not in use):

rm /usr/share/images/desktop-base/login-background.svg

Step 2)
Copy your favored background picture to an appropriate directory. Note, that your home directory should not be the target directory since GDM3 has no permissions to read it. I use to keep the default directory, which actually is /usr/share/images/desktop-base/. While you may use an arbitrary filename, I think the original login-background naming is a good idea because it shows, what this file is for. You should use a filename extension commonly associated with the graphic's format (png for example):

cp /home/$USERNAME/$MYBACKGROUND.PNG /usr/share/images/desktop-base/login-background.png

Step 3)
Edit the file /etc/gdm3/greeter.gsettings by adding the following paragraph to it. This tells your system, what picture should be the login background (here the one of step 2), the zoom option stretches it to fill the entire screen.

# Background picture
[org.gnome.desktop.background]
picture-uri='file:///usr/share/images/desktop-base/login-background.png'
picture-options='zoom'

If the green touch of Linux Mint artworks appearing in the login dialog contrasts with your login-background, you can change this by altering the GDM3 theme. If you change it from Mint-X to Mist for example, the mintish green will be replaced by dark blue. To do so, edit the file /usr/share/linuxmint/adjustments/gdm3/greeter.gconf-defaults: Simply replace the theme's name with your choice (which must be a GTKtheme).

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# Theming options
/desktop/gnome/interface/gtk_theme $MYTHEMECHOICE
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