Learning the Korn Shell, 2nd Edition

Chapter 10. Korn Shell Administration

System administrators use the shell as part of their job of setting up a system-wide environment for all users. In this chapter, we discuss the Korn shell’s features that relate to this task from two perspectives: customization that is available to all users and system security. We assume that you already know the basics of Unix system administration.^[123]

Installing the Korn Shell as the Standard Shell

As a prelude to system-wide customization, we want to emphasize something about the Korn shell that doesn’t apply to most other shells: you can install it as if it were the standard Bourne shell, i.e., as /bin/sh. Just save the real Bourne shell as another filename, such as /bin/bsh, in case anyone actually needs it for anything (which is doubtful), then rename (or link) your Korn shell as /bin/sh.

Many installations have done this with absolutely no ill effects. Not only does this make the Korn shell your system’s standard login shell, but it also makes most existing Bourne shell scripts run faster, and it has security advantages that we’ll see later in this chapter.

As we will see in Appendix A, the Korn shell 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 ...