Hi Guys,
I’have installed opensuse LEAP 42.3 with KDE Desktop. Yesterday i change it with the GNOME one from Yast but coming back to the KDE i did some mistake. I select from DISPLAYMANAGER in the DIsplay Manager ‘‘kde’’ and from DEFAULT_WM ‘‘kde4’’. After that i rebot the system and i obtain a grey login window. If i insert correctly the user and the pasword the system reload the login window. How i can exit from this trouble?
Thanx a lot to everybody.
There is no DISPLAYMANAGER called “kde”, so you get xdm as fallback.
If you did a default KDE installation, this should be “sddm”. “kdm” is still included so you can use that too, but you’d need to install it manually (unless this is an upgrade, then it likely may be installed already).
DEFAULT_WM should be set to “plasma5” or “kde-plasma”, but that actually doesn’t really matter much as you can choose the session on the login screen (and SDDM actually ignores that setting anyway).
Sorry I set ‘‘kdm’’ not ‘‘kde’’.
The problem is that now I can not go any further the login menu. If can be usefull to help me i can load the screenshot of the login window.
And is kdm installed?
As I said, the default installed DM is sddm, kdm has been dropped upstream 3 years ago and is no longer developed.
The problem is that now I can not go any further the login menu. If can be usefull to help me i can load the screenshot of the login window.
A screenshot won’t help much, I do know how xdm looks like… 
What’s the problem though?
Enter your username and password and press RETURN, and you should get logged in.
(although you’d probably end up in a simple twm session instead of Plasma, as DEFAULT_WM is wrong)
Note that you need to keep the mouse cursor over the text input field, otherwise it will lose the focus.
Or press Ctrl+Alt+F1 to switch to text mode, login there and make the changes, then reboot.
At this point I think that it was not installed…
If i insert username, password and press RETURN the screen becomes black as it is loading something and then turn back to the login window.
Now i press Ctrl+Alt+F1 as you said but I don’t know how to make the change now :‘(:’(…sorry but I’m a really new user of Linux
You can run YaST in text mode, or edit /etc/sysconfig/displaymanager with a text editor (vim, nano, pico, joe, emacs would be possible choices in text mode, no idea what you may have installed though)
Or run “sudo zypper in kdm” to install kdm, that should “solve” your problem as well.
i solved it from the YaST text mode 
thank you very very much!!