Startup files

If you want to startup your computer to a DM(Desktop Manger. Like XDM, GDM, Entrance) or to a shell

open /etc/inittab

change the last line in the file to the DM of your choice.

examples:

x:5:respawn:/opt/e17/sbin/entranced -nodaemon
x:5:respawn:/opt/gnome/sbin/gdm -nodaemon
x:5:respawn:/usr/X11R6/bin/xdm -nodaemon

Then you can set the first line in inittab to 5 to startup a DE as default or 3 to startup a shell(usually /bin/bash, you can set it by using chsh) as default.

example:

id:5:initdefault:

You can also specify this one on GRUB cmd-line when you bootup by adding 'init single' (to not load any modules) 'init 3' or 'init 5'.

After INIT X on startup

explanation: after you see INIT 3 (or5) when you startup your computer but before you have logged in: this file /etc/rc.local executes.

When /bin/bash is being used (through xterm or as login shell etc..)

~/.bashrc executes and set's all the ENVIRONMENT VARIABLES for itself. You can put whatever you want here if you want it to startup each time you open an xterm etc.

if you run startx or xinit

~/.xinitrc executes

XDM

From the xdm man page:

First, the xdm configuration file should be set up.  Make  a  directory
       (usually  /usr/X11R6/lib/X11/xdm) to contain all of the relevant files.

       Here is a reasonable configuration file, which could be named  xdm-con-
       fig:

            DisplayManager.servers:            /usr/X11R6/lib/X11/xdm/Xservers
            DisplayManager.errorLogFile:       /var/log/xdm.log
            DisplayManager*resources:          /usr/X11R6/lib/X11/xdm/Xresources
            DisplayManager*startup:            /usr/X11R6/lib/X11/xdm/Xstartup
            DisplayManager*session:            /usr/X11R6/lib/X11/xdm/Xsession
            DisplayManager.pidFile:            /usr/X11R6/lib/X11/xdm/xdm-pid
            DisplayManager._0.authorize:       true
            DisplayManager*authorize:          false

       Note  that  this  file mostly contains references to other files.  Note
       also that some of the resources are specified with ``*'' separating the
       components.  These resources can be made unique for each different dis-
       play, by replacing the ``*'' with the display-name, but  normally  this
       is  not  very useful.  See the Resources section for a complete discus-
       sion.

Note that these can also be in ~/.Xstartup and ~/.Xresources

DE startup files

explanation: when you launch a DE, these files startup things for you.

XFCE, GNOME, KDE

~/Desktop/Autostart/*

KDE

~/.kde/Autostart

Fluxbox

~/.fluxbox/startup

Arch Specific

/etc/rc.conf: Among other things executes modules and the daemons(scripts) inside /etc/rc.d/ at bootup before you have logged in
/etc/rc.d/* - configured deamons for the system.

Notes

make sure the various startup files have execute permissions for your user. here's an example.

chmod a+rwx name-of-startup-file