switchdesk is, as far as I know, a Redhat / Fedora utility. You need to be root for system wide changes, but it should also work for a user.
For Debian:
You can create a .xinitrc file in your home directory, with the line:
This will only affect your account. Deleting ~/.xinitrc will then revert back to system default.
There should also be a file /etc/X11/xinit/xinitrc that is the system wide settings.
I hope this helps
--Ian