RANDOM_LIGHTDM_BG.md

How to set a random lightdm-slick-greeter background

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Currently I don't use a random background in my slick-greeter.conf, but I've wrote a script that handles this in case you want to use it.

I found that the most convenient way to do this for me is to put everything in /usr/share/backgrounds/lightdm.

1. Create a script to select a random image

I've put some wallpapers in Pictures/lightdm, they come from this Reddit thread. Needless to say you can add pictures of your own choice.

The following script selects all PNG items from the directory and picks a random one, you'll have to change this script a bit to use other image extentions.

/usr/share/backgrounds/lightdm/random_background_picker.sh

#!/bin/bash

background_dir="/usr/share/backgrounds/lightdm"
background_files=("$background_dir"/*.png)

# Check if there are any PNG files in the directory
if [ ${#background_files[@]} -eq 0 ]; then
    echo "No PNG files found in $background_dir"
    exit 1
fi

random_index=$((RANDOM % ${#background_files[@]}))
selected_background="${background_files[$random_index]}"

# Replace the "selected_background" file with the selected image
cp "$selected_background" "/usr/share/backgrounds/lightdm/selected_background"

Save this script and make it executable.

chmod +x random_background_picker.sh

2. Configure lightdm-slick-greeter

Or any other greeter that allows you to set a background.

/etc/lightdm/slick-greeter.conf

# add the following line:
background = /usr/share/backgrounds/lightdm/selected_background

3. Create a systemd service

To run this on startup (and before the DM is loaded), create a systemd service that utilizes this script.

/etc/systemd/system/random_lightdm_background.service

[Unit]
Description=Random Background Selector

[Service]
ExecStart=/usr/share/backgrounds/lightdm/random_background_picker.sh

[Install]
WantedBy=multi-user.target

Save the file and enable the service.

sudo systemctl enable random_lightdm_background.service

Finally reboot your system to see if the changes have taken effect.