By default Ubuntu 12.04 uses LightDM as the login manager which looks like the following screenshot. it was very simple to change the login screen background. Now this tutorial explains you how you can easily customize your login screen.
After installing some other desktop environment like Kubuntu etc. Your GRUB loader automatically gets changed. For example after you install Kubuntu via apt-get command, it automatically changes default Ubuntu Boot Loader to blue plasma one. This tutorial explains you how you can gte back to old boot theme.
So first thing you ned to do is click Dash Home icon present on the top of Ubuntu Unity Launcher, type terminal in search box and open it.
Now run the following commands as described:
sudo update-alternatives --config default.plymouth
Choose the option you want.
Followup this with following command:
sudo update-initramfs -u
That’s all. Reboot your machine. It also sets default Ubuntu login screen back.
After installing KDE Plasma desktop in Ubuntu, it automatically takes over your default Ubuntu LigntDM login screen and displays KDM instead. You can easily switch back to LightDM by running a simple command in terminal.
Follow the given steps:
Step-1 So first thing you need to do is click Dash Home icon present on the top of Ubuntu Unity Launcher, type terminal in search box and open it.
Step-2 Second step is to type or copy-paste the following command in the terminal and hit ENTER
sudo dpkg-reconfigure kdm
Step-3 Now there should popping menu on your screen asking you to select default display manager. Use your arrow keys and select LightDM instead or KDM.That’s all with the settings.
Finally restart your PC.