bash Login Scripts

Linux novices often get confused over the number of scripts that are executed when a user logs in. Here's the skinny. First you need to understand:

Login Shells vs Interactive Shells

A login shell is started when you log in at a virtual terminal. As far as bash is concerned, it is started with a "-" as its first argument on the command line, or with the "--login" option.

An interactive shell is a shell that is started from the command line after loggin in, or is started from a window manager after login

So, when you sit down at a Linux desktop system and log in via gdm or kdm - the "graphical login managers" - then start a terminal window containing bash, you are running an interactive shell. On the other hand, if you press Ctrl+Alt+F1 to switch to virtual terminal 1 and then log in, you will be starting a login shell. You can see the difference with the ps aux command:

[les@sleipnir les]$ ps aux | grep bash
les 1358 0.0 0.2 7344 2136 pts/1 S Oct01 0:00 /bin/bash
les 16831 0.0 0.2 7348 2156 pts/2 S 14:49 0:00 -bash
les 16868 0.0 0.2 7356 2160 tty1 S 14:50 0:00 -bash
les 16903 0.0 0.0 3756 564 pts/2 S 14:50 0:00 grep bash
[les@sleipnir les]$

The first line shows an interactive bash shell, running on pts/1 - that was started from within KDE (in fact, pstree will show it as a child of kdeinit). The second line shows a bash shell which was started from an SSH login, running on pts/2. The process name is shown as "-bash", indicating a login shell. The third line shows the login on tty1, which is also a login shell (pstree would show this bash shell as a child of "login".

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