How to start Xorg server with startx

[Yoshinori Arai <kumagusu08@gmail.com>]

Hello,

I'm using slim display manager with ~/.xsession that is symbolic linked to
~/.xinitrc. My xinitrc script include keyboard setting with setxkbmaps, japanese
input method with uim, and exec windowmanager such as cwm, fluxbox at last line.

When I install another windowmanager, I think slim dispkay manager can't select
it by F1 key because new windowmanager desktop file is not in
/run/current-system/profile/share/xsessions but in
~/.guix-profile/share/xsessions.

I have installed xorg-server and xinit and stopped xorg-server service to try to
start Xorg server with startx command. But I couldn't start Xorg server with
error, load module intel, vesa, can't open /dev/tty0 (permission error).

Please tell me how to select windowmanager with F1 key on slim display manager
without system reconfigure and in case using startx command, what configuration
of Xorg is needed. 

Thank you.