Question

there are several startup files which are leveraged by bash please identity the files which are used by this shell. identify the role /purpose of each file and when each files is applied/executed

Answer 1

/etc/profile
Here is a base /etc/profile. This file starts by setting up some helper functions and some basic parameters. It specifies some bash history parameters and, for security purposes, disables keeping a permanent history file for the root user. It also sets a default user prompt. It then calls small, single purpose scripts in the /etc/profile.d directory to provide most of the initialization

The /etc/profile.d Directory

Now create the /etc/profile.d directory, where the individual initialization scripts are placed:

/etc/profile.d/dircolors.sh

This script uses the ~/.dircolors and /etc/dircolors files to control the colors of file names in a directory listing. They control colorized output of things like ls --color. The explanation of how to initialize these files is at the end of this section

/etc/profile.d/extrapaths.sh

This script adds some useful paths to the PATH and can be used to customize other PATH related environment variables (e.g. LD_LIBRARY_PATH, etc) that may be needed for all users.

/etc/profile.d/readline.sh

This script sets up the default inputrc configuration file. If the user does not have individual settings, it uses the global file.

/etc/profile.d/umask.sh

Setting the umask value is important for security. Here the default group write permissions are turned off for system users and when the user name and group name are not the same.

/etc/profile.d/i18n.sh

This script sets an environment variable necessary for native language support. A full discussion on determining this variable can be found on the LFS Bash Shell Startup Files page.

/etc/bashrc

Here is a base /etc/bashrc. Comments in the file should explain everything you need

~/.bash_profile

Here is a base ~/.bash_profile. If you want each new user to have this file automatically, just change the output of the command to /etc/skel/.bash_profile and check the permissions after the command is run. You can then copy /etc/skel/.bash_profile to the home directories of already existing users, including root, and set the owner and group appropriately.

~/.bashrc

Here is a base ~/.bashrc. The comments and instructions for using /etc/skel for .bash_profile above also apply here. Only the target file names are different.

~/.bash_logout

This is an empty ~/.bash_logout that can be used as a template. You will notice that the base ~/.bash_logout does not include a clear command. This is because the clear is handled in the /etc/issue file.

/etc/dircolors

If you want to use the dircolors capability, then run the following command. The /etc/skel setup steps shown above also can be used here to provide a ~/.dircolors file when a new user is set up. As before, just change the output file name on the following command and assure the permissions, owner, and group are correct on the files created and/or copied.

If you want to use the dircolors capability, then run the following command. The /etc/skel setup steps shown above also can be used here to provide a ~/.dircolors file when a new user is set up. As before, just change the output file name on the following command and assure the permissions, owner, and group are correct on the files created and/or copied.