(services (cons* (console-keymap-service "dvorak")
(gnome-desktop-service)
(xfce-desktop-service)
(modify-services %desktop-services
(slim-service-type config =>
(slim-configuration
(
startx (xorg-start-command
(xorg-configuration-file
'("Section \"InputClass\"
Identifier \"keyboard-all\"
Option \"XkbLayout\" \"dvorak\"
MatchIsKeyboard \"on\"
EndSection")))))))))
This successfully fixed the problem in the login manager. (GNOME, of
course, had to be configured separately.)