System administration is the job of keeping a system up and running, and providing a suitable environment for whatever work the system is doingwhether it's serving Web pages, being used for software development, or acting as a workgroup file server.
As we've mentioned, Max OS X comes in two versions, the version that we cover in this book (Mac OS X Tiger) and another version called Mac OS X Server Tiger. The two versions are almost identical but do have some differences. For example, Access Control Lists (ACLs) are turned on by default in Mac OS X Server. Mac OS X Server also comes with an iChat server, a Weblog server, and Xgrid (which enables turning a group of Macs into a supercomputer). If you are working on Mac OS X Server, everything in this chapter will work for you, but you'll need to learn about some additional tools.
Most Mac OS X users are working on single- user desktop machines, but some of you are stepping out into the strange new world of running a multiuser system. Perhaps you're giving friends accounts on your machine so that they can ssh in and edit Web pages, or running a mail server with accounts for dozens of colleagues. If so, you are starting to be concerned about backing up your users' data (at least you should be concerned about it!), managing users' accounts and permissions on the system, and troubleshooting problems for other people. You have now fallen into what may seem like the rabbit hole of system administration, where everything appears strange. This chapter will help you transcend that complexity and become the author of your own Wonderland, where in our worldthe Unix worldyou will be known as a sysadmin .
In this chapter we will give you a whirlwind tour of the basic elements of system administration. We're sure the information here will provide a good basis for learning even more as your skills and interest grow. Please note that most of the tasks in this chapter assume that you are logged in as an admin user . Admin users are specific to Mac OS X and are accounts that have been set to "allow user to administer this computer" when the account was created (see "Adding and deleting users with System Preferences," later in this chapter). Mac OS X admin users have a very powerful capacitya capacity known in the wider Unix world as "having root." That is, they have the ability to execute any command on the system with the privileges of the all-powerful root account. The first thing a system administrator needs to learn about is the power of root.