There are two areas in which system administrators use the shell as part of their job: setting up a generic environment for users and system security. In this chapter, we’ll discuss bash’s features that relate to these tasks. We assume that you already know the basics of UNIX system administration. 
As a prelude to system-wide customization, we want to emphasize that bash can be installed as if it were the standard Bourne shell, /bin/sh. Indeed, some systems, such as Linux, come with bash installed instead of the Bourne shell.
If you want to do this with your system, you can just save the original Bourne shell to another filename (in case someone needs to use it) and either install bash as sh in the /bin directory, or better yet install bash in the /bin directory and create a symbolic link from /bin/sh to /bin/bash using the command ln -s /bin/bash /bin/sh. The reason we think that the second option is better is because bash changes its behavior slightly if started as sh, as we will see shortly.
As detailed in Appendix A, bash is backward-compatible with the Bourne shell, except that it doesn’t support ^ as a synonym for the pipe character |. Unless you have an ancient UNIX system, or you have some very, very old shell scripts, you needn’t worry about this.
But if you want to be absolutely sure, simply search through all shell scripts in all directories in your PATH. An easy way to perform the search is ...