Which configuration file is read first when a login bash shell is executed?

When a login bash shell is executed, the first configuration file that is read is /etc/profile. This file contains system-wide settings and configurations that are applied to all users on the system when they log into a bash shell. It sets up the environment for users, defining variables and executing scripts that configure the shell environment before the user-specific configurations are applied.

After /etc/profile is executed, if a user-specific configuration file exists, such as ~/.bash_profile, it would be read to apply personalized settings for that user. The ~/.bashrc file is generally executed for non-login interactive shells and is not read during the initial login process. Similarly, /etc/bash.bashrc applies to non-login shells and is executed for each interactive shell session thereafter. Thus, it is important to recognize that /etc/profile is the foundational configuration file that sets the stage for user-specific configurations upon the initial login.