Setting the keyboard layout globally for desktop

Unfortunately during installation I skipped unintentionally the keyboard configuration and the layout is US (default). Now of course any user can set the keyboard layout in his desktop session, but this is undesirable and, anyway, the login manager keeps on seeing the default US keyboard.
When I started using the X environment there was still a file name XF86Config, but things must have changed quite a lot. Where am I supposed to operate?

Thanks in advance!

Andrea

UPDATE
Is a command like localectl set-keymap it the way?

Hi Andrea,

Yes, localectl set-keymap is the correct way to set this. It will change the layout used on the text console and graphical user interfaces.