Running xdm manually
xdm uses the X server to run on your local display. Therefore, you must have a working X configuration prior to using a display manager. Then, to start xdm, simply enter it as root:
xdm launches the X server and displays the graphical login, and you can log in as usual. xdm then starts your graphical environment. After you log out, xdm resets and again displays the login screen.
Most Linux distributions enable virtual consoles. You can switch among them using the key combinations Ctrl-Alt-F1, Ctrl-Alt-F2, and so on. (The Ctrl is required only when switching from an X console to a text or other X console.) Typically, the first six consoles are set up as text-mode screens, and X launches on console 7 (Ctrl-Alt-F7) or the first TTY not running mingetty or some other getty process. This means that, as with startx, your original text-mode console remains unchanged after you manually start xdm. Therefore, you must log out of your text-mode console if you plan to leave the system unattended with xdm running manually.
If you want to stop xdm, you first must be sure that all of the X sessions under its management are logged out. Otherwise, they’ll die when xdm exits and you could lose data. Simply stop the xdm process using kill or killall from a text console:
Of course, xdm isn’t very useful for your local system if you must always start it manually. That’s why most Linux distributions include a boot-time option to start xdm for you, eliminating the text-mode ...