Linux User Process Startup

In Linux, what happens after a user logs in depends on the type of login:

• Character-mode (shell) login:

  This type of login happens from a terminal, pseudo-terminal, network connection (rsh, ssh, telnet), or from the conosle if not in GUI mode.

  The details depend on which shell is started, but each shell is similar. For our purposes here let's assume the BASH shell which is the most common shell in Linux.

  Once a login shell is started it runs two scripts to initialize the shell environment:

  • /etc/profile
  • $HOME/.bash_profile, or if that file is not present then $HOME/.profile
  • If there is a file specified by the environment variable, $BASH_ENV then that file is also run. (This file is also run by non-login shells when they start. It's purpose is to initialize data that is not passed to children, such as aliases.)

• Graphical (GUI) login:

  Once a user logs in, gdm-binary then starts gnome-session. This drives the Gnome login session. Gnome-session then starts other processes including:

  • The Window Manager. This program positions windows on the screen and draws the screen border, including the title bar and the widgets on the title bar. There are several window managers to choose from, and each user can pick his/her own. The normal window manager for gnome is Metacity.
  • A screensaver (which is initially inactive but watches for the keyboard and mouse to go idle in order to activate).
  • gnome-panel which displays the panel(s) at the edges of the screen. These panels provide much of the user interface to gnome.
  • nautilus which displays file-system windows when needed for the home directory, file system, etc. based on icons on the desktop.
  Once the desktop has initialized, the user can interact with the system. For example, using the interface provided by the desktop manager, the user can start gnome-terminal, which offers a bridge between character-mode programs (started by gnome-terminal) and the GUI environment (in which gnome-terminal lives). Gnome-terminal is most often used to run a shell.

  Return to main PC Boot Sequence page

  Return to my writing page

  Return to my home page