Change background wallpaper randomly on Ubuntu 8.10 (Intrepid Ibex)

Get bored with the default wallpaper? If yes, let's have some fun!

1. download suitable wallpapers from art.gnome.org using ftp. Assume your screen resolution is 1280x1024, so we can download all the wallpapers from art.gnome.org into $HOME/Pictures/Wallpapers/art.gnome.org. Please create the directory yourself :-)
   

   ftp ftp.gnome.org 
   Connected to ftp.acc.umu.se. 220 (vsFTPd 2.0.6) 
   Name (ftp.gnome.org:root): anonymous 
   331 Please specify the password. 
   Password: 
   230 Login successful. Remote system type is UNIX. Using binary mode to transfer files. 
   ftp> cd /pub/GNOME/teams/art.gnome.org 
   250 Directory successfully changed. 
   ftp> bin 
   200 Switching to Binary mode. 
   ftp> prompt off 
   Interactive mode off. 
   ftp> mget *1280x1024.jpg 

   Ok, now you should have lots of wallpapers ready to load.
2.  Change to a random wallpaper from command line
   export WALLPAPER_DIR=$HOME/Pictures/Wallpapers
/usr/bin/gconftool-2 -t str -s /desktop/gnome/background/picture_filename "`find $WALLPAPER_DIR -name \*.jpg | sort -R | tail -n 1`"

3. Pretty cool right? Now let’s create a shell so you don’t need to remember it each time. Save it as $HOME/bin/random_wallpaper
   #!/bin/sh
   echo "Changing to a random wallpaper"
   WALLPAPER_DIR=$HOME/Pictures/Wallpapers
   /usr/bin/gconftool-2 -t str -s /desktop/gnome/background/picture_filename "`find $WALLPAPER_DIR -name \*.jpg | sort -R | tail -n 1`"
    
4. Setup a cronjob to run the script every minute! no, every 10 minutes maybe better. Make sure your user account in /etc/cron.allow otherwise it won’t run your script!
   
   chmod a+x $HOME/bin/random_wallpaper
   crontab -e
   */10 * * * * /home/hkai/bin/random_wallpaper
    
5. Its running but the wallpaper is not changing! Why, I’m not sure, should be some environment parameters related to Dbus or Xauthority. So we need to put the environment into the script each time we login since it’s changing each time you login to gnome.
   DBUS_SESSION_BUS_ADDRESS=unix:abstract=/tmp/dbus-wqQ5W7fMS4,guid=6b489fd5651208f06087bb45492cb471
   XAUTHORITY=/tmp/.gdmN7XVKU
   
   So we need another script which generate the random_wallpaper each time after we login. Save it as $HOME/bin/generate_wallpaper_script
   #!/bin/sh
   
   SCRIPT_FILE=$HOME/bin/random_wallpaper
   WALLPAPER_DIR=$HOME/Pictures/Wallpapers
   
   # Export the dbus session address on startup so it can be used by cron
   echo ‘#!/bin/sh\n\n’ > $SCRIPT_FILE
   
   echo ‘echo “Changing to a random wallpaper”\n’ >>$SCRIPT_FILE
   echo ‘WALLPAPER_DIR=’$WALLPAPER_DIR >>$SCRIPT_FILE
   echo ‘export WALLPAPER_DIR’ >>$SCRIPT_FILE
   
   env | grep DBUS_SESSION_BUS_ADDRESS >> $SCRIPT_FILE
   echo ‘export DBUS_SESSION_BUS_ADDRESS’ >> $SCRIPT_FILE
   env | grep XAUTHORITY >> $SCRIPT_FILE
   echo ‘export XAUTHORITY’ >> $SCRIPT_FILE
   
   echo ‘echo “Old wallpaper:” `/usr/bin/gconftool-2 -g /desktop/gnome/background/picture_filename`’ >> $SCRIPT_FILE
   
   echo ‘/usr/bin/gconftool-2 -t str -s /desktop/gnome/background/picture_filename “`find $WALLPAPER_DIR -name \*.jpg | sort -R | tail -n 1`”‘ >> $SCRIPT_FILE
   
   echo ‘echo “New wallpaper:” `/usr/bin/gconftool-2 -g /desktop/gnome/background/picture_filename`’ >> $SCRIPT_FILE
    
6. Now add the script into gnome session so it will run each time after you login.
   Wait 10 minutes see if the wallpaper is changing and relax.
   
7. I'd uploaded the script here. generate_wallpaper_script