Put the system with the Russian keyboard layout, password English.
and
Now in KDM Russian layout is, and we must constantly switch it. Where it change?
It is not very clear to what you must switch

The keyboard layout for root and/or language setting for Login Screen (KDM).
Here is a manual for both of them.
Keyboard layout for root;
1. In KDM > Menu > Console Login > OK
2. ......... login:
root3. Password: <password of root>
4. ......... ~#
startx (command to start KDE)
5. System Settings > Input Devices > Keyboard > Layouts > ....
6. Restart Computer.
Language setting for Login Screen (KDM)
(can be done as normal user)
1. System Settings > Login Screen > General > Locale Language: .....
I hope this will solve you problem
