Debian X session 啟動設定及腳本目錄

/etc/X11/Xsession.options 
/etc/X11/Xsession.d/
/etc/xdg/autostart
/usr/share/xfce4/panel/plugins

The Debian reference manual describes how the defaults work:
If the user has a ~/.xsessionrc file, read it.
If a specific session was selected in the DM (GDM, KDM, WDM, LightDM, ...) , run it.
Otherwise, if the user has a ~/.xsession or ~/.Xsession file, run it.
Otherwise, if the /usr/bin/x-session-manager command exists, run it.
Otherwise, if the /usr/bin/x-window-manager command exists, run it.
Otherwise, if the /usr/bin/x-terminal-emulator command exists, run it.