User settings at login

When a user logins, getty gives him SHELL.

In case of /bin/bash, the following initialization/configuration scripts are executed:

`/etc/profile`	System wide initialization file. Runs at log in.
`~/.bash_profile`	Executed automatically after `/etc/profile`
`~/.bash_login`	If `~/.bash_profile` is absent, the script is executed after `/etc/profile`, otherwise, ignored.
`~/.profile`	If both `~/.bash_profile` and `~/.bash_login` are absent, the script is executed after `/etc/profile`, otherwise, ignored.
`~/.bashrc`	It is called from `~/.bash_profile` at startup. An interactive shell that is not a login shell also reads `~/.bashrc` .
`~/.bash_logout`	Executed automatically during log out
`~/inputrc`	Contains optional key bindings

When you need to specify environment variables, for example PATH, you can place them in /etc/profile for all users on the system, or in ~/.bashrc for the specific user.

When the user logs out, control returns to init, which wakes up and spawns a new getty on the terminal port.

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