How to change wallpapers of all clients?

Set up a cron job on all machines that executes a script where you check 1 specific place for new images. Sample (untested) script with wget and ftp:

#!/bin/bash
wget -N -r -nH --cut-dirs=2 -t 180 -P /tmp ftp://user:[email protected]/dir/backgroundimage.gif
gconftool-2 --type string --set /desktop/gnome/background/picture_filename /tmp/backgroundimage.gif

Basically the 2nd line needs to be altered to the method you use to manually load the image to the machines. And then set up cron to execute this script to check every hour or once a day for new images.

You could even set it up to fetch a script where that script gets excecuted on the client machine and it then fetches the images and changes the background with gconftool-2. This would allow you to execute more than changing a background.

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You can create a cron job with sudo crontab -e. This will show a line similar to this:

# m h  dom mon dow   command

(m minutes, h hour, dom day of month, mon month, dow day of week) and underneath it you could add ...

0 * * * /path/to/executable

or

@hourly     /path/to/executable

to have /path/to/executable run every hour on the hour. Mind you: a script you put in here does not understand the path variable unless you include it. You can put this at the top to include $SHELL and $PATH:

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

Otherwise you need to make sure your script uses full path names to execute commands. More info on cron can be found on the Ubuntu wiki.

You can also use the /etc/cron.hourly directory to put a script there that gets run every hour. Example topics regarding the last part: What's wrong with my cron.hourly configuration? and Cron.hourly won't run.

It may be worth it to install a remote admin framework like puppet. It usually takes some time to properly install and configure it for your network, but once it's there it's quite easy to copy files to all the machines (or just a subset of them), run scripts on them and such.

You can make the wallpaper setting mandatory, meaning that users will not be able to customize their background.

In Ubuntu 11.04 and earlier, this command should work:

sudo gconftool-2 --direct --config-source \
xml:readwrite:/etc/gconf/gconf.xml.mandatory --type string --set \
/desktop/gnome/background/picture_filename \ 
"/usr/share/backgrounds/cosmos/blue-marble-west.jpg"

In Ubuntu 11.10 (or any GNOME 3 system), you should be able to do this with:

1. Create a file /etc/dconf/profile/user with the contents:

   user
   site
   

2. Make a default setting by creating a file /etc/dconf/db/site.d/background with the contents:

   [org/gnome/desktop/background]
   picture-uri='file:///usr/share/backgrounds/company-wallpaper.jpg'
   

3. And finally make the default mandatory by creating /etc/dconf/db/site.d/locks/background with the contents:

   /org/gnome/desktop/background/picture-uri
   

4. dconf settings need to be compiled to work so run sudo dconf update The first time you run this, you'll need to reboot to see the effect. Currently, there's a bug where users will still see the normal Background chooser; it just won't actually change the background.

Combine this solution with something like puppet to propogate this setting to all the computers in your company!