xinitrc

xinitrc is a shell script used by the X Window System to configure and start an X session. It is executed by the xinit program (and by the startx wrapper) to launch the window manager and any other programs that should run when an X session begins. The script allows a user to customize the startup sequence, controlling which applications, panels, background, and services start automatically for the session.

Location and precedence are as follows: a system-wide default is typically provided at /etc/X11/xinit/xinitrc, while users may create a personal copy at ~/.xinitrc. When a user-specific ~/.xinitrc exists, startx/xinit will use it in preference to the system default; otherwise the system-wide script is used. Some setups may source or include the system default from the user file to reuse common settings.

Contents and structure are generally simple and rely on the shell. A typical xinitrc loads X resources, launches background settings, and ends with an exec command to start the window manager or desktop session. Common elements include loading resources with xrdb -merge ~/.Xresources, setting a wallpaper, and starting a window manager or session, such as exec openbox-session, exec i3, or exec startwm.sh. The final line must be an exec to replace the shell process with the window manager, ensuring proper session lifecycle.

Relation to other session mechanisms: xinitrc is specific to the traditional xinit/startx workflow. Display managers (logind or graphical login programs) use their own session initiation files (such as Xsession or a display-manager-specific script) and may invoke ~/.xinitrc or a similar mechanism as part of starting an X session, depending on the system.

In summary, xinitrc provides a user-controllable entry point for launching and configuring an X session, with user-level customization taking precedence over the system default.