Login procedure in Linux

User can login locally into the console when in runlevel # 3 or graphically when in runlevel # 5 (the level numbers may differ depending on the distribution). In both cases you need to provide username and password. Bash uses the following initialization and start-up files:

1. /etc/profile - The systemwide initialization file, executed for login shells.
2. /etc/bash.bashrc - The systemwide per-interactive-shell startup file. This is a non-standard file which may not exist on your distribution. Even if it exists, it will not be sourced unless it is done explicitly in another start-up file.
3. /etc/bash.logout - The systemwide login shell cleanup file, executed when a login shell exits.
4. $HOME/.bash_profile - The personal initialization file, executed for login shells.
5. $HOME/.bashrc - The individual per-interactive-shell startup file.
6. $HOME/.bash_logout - The individual login shell cleanup file, executed when a login shell exits.
7. $HOME/.inputrc - Individual readline initialization file.