We cannot change the theme of Login screen of Gnome 3 GDM. We can only change the background image of the login screen. If you change that frequently then you will get a fresh feel of the operating system.
I tried this on Fedora 15 and worked well
GDM Customization
# su - gdm -s /bin/bash $ dbus-launch
This command will print DBUS_SESSION_BUS_ADDRESS and DBUS_SESSION_BUS_PID. We need to export them
$ export DBUS_SESSION_BUS_ADDRESS=unix:abstract=/tmp/dbus-Jb433gMQHS,guid=fc14d4bf3d000e38276a5a2200000d38 $ export DBUS_SESSION_BUS_PID=4283
Check to see if dconf-service is running and if not, start it like this
$ /usr/lib/dconf/dconf-service &
Wallpaper
$ GSETTINGS_BACKEND=dconf gsettings get org.gnome.desktop.background picture-uri $ GSETTINGS_BACKEND=dconf gsettings set org.gnome.desktop.background picture-uri "file:///usr/share/backgrounds/gnome/SundownDunes.jpg"
You will need to point to a file where the gdm user has permission to read, not in your home directory.
Start program automatically after login to GNOME 3
You can specify which programs to start automatically after login using the gnome-session-properties tool, which is a part of the gnome-session package.
$ gnome-session-properties
Turning off the sound
$ GSETTINGS_BACKEND=dconf gsettings set org.gnome.desktop.sound event-sounds false
Start program automatically after login to GNOME 3
You can specify which programs to start automatically after login using the gnome-session-properties tool, which is a part of the gnome-session package.
$ gnome-session-properties
There is lot more tweaks at Arch Linux Wiki about gnome 3.
Related articles
- LightDM To Replace GDM And Dialog Sheets To Make An Appearance In Ubuntu 11.10 (techie-buzz.com)
- Martin Owens: How to Make a Gnome Login Screen (in Python) (doctormo.org)
- Ubuntu 11.10 To Switch From GDM To LightDM (digitizor.com)
- Bilal Akhtar: GNOME3 on Ubuntu using the PPA (ubunturocking.wordpress.com)
- Ubuntu adopts LightDM, login screens to get more exciting (geek.com)
- GNOME3 packages begin trickling into Ubuntu 11.10 (omgubuntu.co.uk)
- Change Login Screen Resolution (martinwebster.eu)
- Vincent Untz: gnome-panel is dead, long live gnome-panel! (vuntz.net)
- Install Gnome 3 on ubuntu 11.04 Ubuntu 10.10 (ranjith.zfs.in)

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Can yoou suggest any other blogs/websites/forums
that cover the same topics? Thank you!