[Live-demo] changing the login screen backdrop on ubuntu 10.04 and 12.04

[Hamish]

Hi,

I don't think I've posted these notes yet & I'm not sure if they'll be
needed or not.

with 12.04 xubuntu has switch to lightdm instead of gdm for its login screen.
actually gdm takes a bit less memory to run at the current versions, but is
just fresh from a rewrite so maybe similarly buggy to the newly written
lightdm.

in the past we'd manually set gdm's auto-login config, and fortunately
lightdm is controlled by text files in /etc/lightdm/ not gnome's gconf
editor, so it's pretty simple to do, see /etc/lightdm/lightdm.conf.

one question that came up in the past is what if we wanted to change the
backdrop on that login screen to have some text saying what the pswd was
etc. with the current setup you only see that screen if you log out, which
you might do to change the language. If you didn't read the notes you
wouldn't otherwise know what the pre-set pswd was.  /shrug

anyway, if you ever want to do it, here it is. As a bonus for archive
searchers I'll throw in how to do it on Lucid too, and how to set up dual
monitors with lightdm's login screen on xubuntu 12.04.


ubuntu 10.04 lucid:

# set the image
sudo -u gdm gconftool-2 --set --type string \
   --set /desktop/gnome/background/picture_filename \
         /usr/local/share/images/your_new_background.jpg

(default is /usr/share/backgrounds/warty-final-ubuntu.png)

# also, you might want to scale it differently:
sudo -u gdm gconftool-2 --set --type string \
         --set /desktop/gnome/background/picture_options scaled

#scaling options are none, wallpaper (tiled), centered, scaled,
#  stretched, zoom, and spanned (across 2 monitors)


# if not stretching to full screen, do this to avoid purple borders:
sudo -u gdm gconftool-2 --set --type string \
     --set /desktop/gnome/background/primary_color "#000000"


----------------------------

ubuntu 12.04 precise:

lightdm background image is pretty easy:
  edit /etc/xdg/lubuntu/lightdm/lightdm-gtk-greeter.conf


To change the background image in GDM (regular ubuntu not xubuntu)

from  http://smashingweb.ge6.org/change-the-background-of-gnome-3-gdm-login-screen/

quoted:

"""
# su - gdm -s /bin/bash
$ dbus-launch

The above 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 &

Set the 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.
"""

then as root restart the gdm service.

for precise I had to "chown gdm.gdm /var/lib/gdm/.config -R" first, as root owned that not the gdm user, so the gdm user couldn't write the file.
seems like an oversight.


-------

finally, dual monitor setup for the login screen:

[if you installed the nVidia proprietary driver you can save an X.org
config file with that already set up, otherwise do this]

 (gdm on ubuntu 12.04)
- run arandr and make a setup script
- move it to /usr/local/bin/dual-monitors.sh
- edit /etc/gdm/Init/Default

add "/usr/local/bin/dual-monitors.sh" before gdmwhich()


lightdm on ubuntu 12.04:
- same as above, add script to 

cat << EOF >> /etc/lightdm/lightdm.conf

[SeatDefaults]
greeter-session=lightdm-gtk-greeter
user-session=xubuntu
display-setup-script=/usr/local/bin/dual-monitors.sh
EOF



maybe it helps sometime,
Hamish