Linux Variables

When a user logs in, an environment is created for that user automatically. This happens based on the following four configurations files:

/etc/profile -> Generic file that is processed by all users upon login. For a login shell only
/etc/bashrc -> This file is processed when subshells are started. For any shell
~/.bash_profile -> User-specific login shell variables can be defined
~/.bashrc -> Subshell variables are defined
~/.bash_logout -> Commands to execute anytime when you log out.

To update and apply source .bashrc

You shouldn’t edit this files directly. On Linux, may configuration files are used like for example for /etc/profile there is a /etc/profile.d This approach ensures that if the default configuration files are updated as well during a system update you’ll never lose your changes.

To display messages during the login process, Bash uses the /etc/motd and the /etc/issue files. Messages in /etc/motd display after a user has successfully logged in to a shell.

if you put color=blue only applies in that subshell export color=blue