usrbinXsession

usrbinXsession, commonly referred to by the path /usr/bin/Xsession, is a shell script used by display managers in Unix-like systems to start a user session under the X Window System. It serves as a standardized entry point for launching the user’s chosen desktop environment or window manager and coordinates the initial environment setup required for an X session.

Location and role: In many Linux distributions, Xsession is provided by the x11-common package (for example on Debian and Ubuntu) or by a closely related package on other distros. Display managers such as GDM, LightDM, SDDM, or XDM invoke this script to begin a graphical session, passing along the user’s selected session type.

Operation: Xsession delegates much of its work to /etc/X11/Xsession, which aggregates environment and startup logic from a set of scripts in /etc/X11/Xsession.d. It determines which session to start by consulting the available desktop session definitions located in /usr/share/xsessions (and sometimes user-selected options). The script then executes the appropriate session command or desktop-specific startup script (for example, a session like GNOME, KDE, XFCE, or a window manager). It also handles environment variables such as DISPLAY, XAUTHORITY, DESKTOP_SESSION, and XDG_CURRENT_DESKTOP, and may source an optional ~/.xsessionrc for per-user tweaks.

Customization and considerations: Changes to the system-wide startup process are typically made by editing the scripts in /etc/X11/Xsession.d or by adjusting the desktop environment’s own startup files. Improper modifications can prevent a graphical login, so changes are usually performed with caution. This script is a foundational component ensuring consistent session initialization across diverse desktop environments.

See also: X session, X11, display manager, /usr/share/xsessions, /etc/X11/Xsession, /etc/X11/Xsession.d.