Where do I set the lockscreen image path in Trusty?

Question

I don't want my desktop session wallpaper to be used as lockscreen background.

Thank you

Answer 1

Found a per user setting : launch dconf-editor then untick com.canonical.unity-greeter draw-user-backgrounds.

For a system wide setting the way is the same as for disabling greeter to use wallpapers and setting a common one from /usr/share/backgrounds:

Set a background with Ubuntu-tweak or

sudo -i
su lightdm -s /bin/bash
gsettings set com.canonical.unity-greeter background '/usr/share/backgrounds/MyTrusty.jpg'
gsettings set com.canonical.unity-greeter draw-user-backgrounds 'false'

Answer 2

If you mean the Login Screen you can change it for example with help of Ubuntu-Tweak.

1. Install:

   sudo apt-add-repository ppa:tualatrix/ppa
   sudo apt-get update
   sudo apt-get install ubuntu-tweak
   

2. Open Ubuntu-Tweak from Dash

3. Navigate to Tweaks > Login Settings
4. Click unlock and enter your sudo password
5. Set desired background image

For more look here