The shell program /bin/bash uses a collection of startup files to help create an environment. Each file has a specific use and may affect login and interactive environments differently. The files in the /etc directory generally provide global settings. If an equivalent file exists in your home directory it may override the global settings.

An interactive login shell is started after a successful login, using /bin/login, by reading the /etc/passwd file. This shell invocation normally reads /etc/profile and its private equivalent ~/.bash_profile upon startup.

# Beyond Linux From Scratch - Version 2013-03-16
# Chapter 3. After LFS Configuration Issues
# -- http://www.linuxfromscratch.org/blfs/view/svn/postlfs/profile.html