It's easy to identify the most important issues and concerns system managers face, regardless of the type of computers they have. Almost every system manager has to deal with user accounts, system startup and shutdown, peripheral devices, system performance, security the list could go on and on. While the commands and procedures you use in each of these areas vary widely across different computer systems, the general approach to such issues can be remarkably similar. For example, the process of adding users to a system has the same basic shape everywhere: add the user to the user account database, allocate some disk space for him, assign a password to the account, enable him to use major system facilities and applications, and so on. Only the commands to perform these tasks are different on different systems.
In other cases, however, even the approach to an administrative task or issue will change from one computer system to the next. For example, "mounting disks" doesn't mean the same thing on a Unix system that it does on aVMS orMVS system (where they're not always even called disks). No matter what operating system you're using Unix, Windows 2000, MVS you need to know something about what's happening inside, at least more than an ordinary user does.
Like it or not, a system administrator is generally called on to be the resident guru. If you're responsible for a multiuser system, you'll need to be able to answer user questions, come up with solutions to problems that are more than just band-aids, and more. Even if you're responsible only for your own workstation, you'll find yourself dealing with aspects of the computer's operation that most ordinary users can simply ignore. In either case, you need to know a fair amount about how Unix really works, both to manage your system and to navigate the eccentric and sometimes confusing byways of the often jargon-ridden technical documentation.
This chapter will explore the Unix approach to some basic computer entities: files, processes, and devices. In each case, I will discuss how the Unix approach affects system administration procedures and objectives. The chapter concludes with an overview of the standard Unix directory structure.
If you have managed non-Unix computer systems, this chapter will serve as a bridge between the administrative concepts you know and the specifics of Unix. If you have some familiarity with user-level Unix commands, this chapter will show you their place in the underlying operating system structure, enabling you to place them in an administrative context. If you're already familiar with things like file modes, inodes, special files, and fork-and-exec, you can probably skip this chapter.