If you use startx rather than a display manager and have GNOME or KDE installed, add
to your ~/.xsessionrc.
Until you have learned to use Xmonad, you will want to keep an existing desktop environment available in the system. Xmonad is a possible alternative to Gnome for example. Invoke update-alternatives to have Xmonad take precedence. In this example, openbox is the extant alternative and xmonad is chosen.
me@computer:~$ sudo update-alternatives --config x-window-manager There are 2 choices for the alternative x-window-manager (providing /usr/bin/x-w indow-manager). Selection Path Priority Status ------------------------------------------------------------ * 0 /usr/bin/openbox 90 auto mode 1 /usr/bin/openbox 90 manual mode 2 /usr/bin/xmonad 20 manual mode Press enter to keep the current choice[*], or type selection number: 2 update-alternatives: using /usr/bin/xmonad to provide /usr/bin/x-window-manager (x-window-manager) in manual mode.
Log out and in again to work in Xmonad. Initially it will present a black screen. Type <Alt>+<Shift>+<Enter> to open a terminal and a selection cursor will appear. The guided tour in http://xmonad.org/documentation.html will be helpful to a novice. After experimenting with Xmonad, run update-alternatives again to reset the window manager. After another logout-login cycle of a display manager or another startx, the more familiar desktop environment should be running.
Xmonad in Debian
Xmonad and its community-maintained extension modules (contrib) can be installed via the standard repositories:
# aptitude install xmonad libghc6-xmonad-dev libghc6-xmonad-contrib-dev
The suckless-tools package is also recommended as it provides dmenu, a simple application launcher which integrates nicely with Xmonad.
Xmonad - Wikpedia article
http://xmonad.org - Xmonad project homepage
Using xmonad in GNOME - haskellwiki article
Xmonad.Config.Gnome - API documentation for Xmonad's GNOME-integration extension