(Tested on Ubuntu Gnome Shell 16.04+)
Two ways. If you want to know what exactly you are doing, follow Solution #1. If you want a single script to do all for you, follow Solution #2 (All it does it automate Solution #1)
Solution 1
Background Info: Gnome Login Background is not a parameter which you can change directly (weird!). It's present within Gnome Shell CSS file which is present in binary file. Hence, you have to extract binary file, modify it, and replace new binary with old file.
Step1: Extracting Gnome shell binary file
Run the following script extractgst.sh to extract Gnome shell theme to ~/shell-theme directory
#!/bin/sh
workdir=${HOME}/shell-theme
if [ ! -d ${workdir}/theme ]; then
mkdir -p ${workdir}/theme
fi
gst=/usr/share/gnome-shell/gnome-shell-theme.gresource
for r in `gresource list $gst`; do
gresource extract $gst $r >$workdir/${r#\/org\/gnome\/shell/}
done
Step2: Modifying it
- Copy your background image to this folder
~/shell-theme/theme.
- Create file
~/shell-theme/theme/gnome-shell-theme.gresource.xml with content
- Replace filename with your background image filename
Now, open the gnome-shell.css file in the directory and change the #lockDialogGroup definition as follows:
#lockDialogGroup {
background: #2e3436 url(filename);
background-size: [WIDTH]px [HEIGHT]px;
background-repeat: no-repeat;
}
Set filename to be the name of the background image and background-size to your resolution.
Step3: Create new Gnome shell theme binary and replacing existing
Inside theme directory, run
glib-compile-resources gnome-shell-theme.gresource.xml
You will get a binary file. Copy it to
/usr/share/gnome-shell
Now restart GDM using
service gdm restart
If it doesn't work or got stuck, restart your computer to see your new login wallpaper :))
Solution 2
Ok, as promised, there is a simpler way to automate all this. Simply save this script as login-background.sh
WORKDIR=~/tmp/gdm-login-background
GST=/usr/share/gnome-shell/gnome-shell-theme.gresource
GSTRES=$(basename $GST)
mkdir -p $WORKDIR
cd $WORKDIR
mkdir theme
for r in `gresource list $GST`; do
gresource extract $GST $r >$WORKDIR$(echo $r | sed -e 's/^\/org\/gnome\/shell\//\//g')
done
cd theme
cp "$IMAGE" ./
echo "
#lockDialogGroup {
background: #2e3436 url(resource:///org/gnome/shell/theme/$(basename $IMAGE));
background-size: cover;
background-repeat: no-repeat;
}" >>gnome-shell.css
echo '<?xml version="1.0" encoding="UTF-8"?>
<gresources>
<gresource prefix="/org/gnome/shell/theme">' >"${GSTRES}.xml"
for r in `ls *.*`; do
echo " <file>$r</file>" >>"${GSTRES}.xml"
done
echo ' </gresource>
</gresources>' >>"${GSTRES}.xml"
glib-compile-resources "${GSTRES}.xml"
sudo mv "/usr/share/gnome-shell/$GSTRES" "/usr/share/gnome-shell/${GSTRES}.backup"
sudo mv "$GSTRES" /usr/share/gnome-shell/
rm -r $WORKDIR
if [ "$CREATED_TMP" = "1" ]; then
rm -r ~/tmp
fi
Run the script using
IMAGE=~/Bat.jpg sh login-background.sh
Now restart gdm using service gdm restart or restart laptop for your new login background :))
References:
https://wiki.archlinux.org/index.php/GDM
https://bbs.archlinux.org/viewtopic.php?id=197036
