Understanding Basic Security
Christine Bresnahan, Richard Blum · 2012
This chapter describes how to understand basic security and identify user types. Accounts enable multiple users to share a single computer without causing one another too much trouble. They also enable system administrators to track who is using system resources and, sometimes, who is doing things they shouldn't be doing. Account features help users use a computer and administrators administer it. Understanding these features is the basis for enabling you to manage accounts. Some account features help you identify accounts and the files and resources associated with them. Knowing how to use these features will help you track down account-related problems and manage the computer's users. Linux permits multiple users to access the computer simultaneously. Most often, this is done by means of remote access servers such as the Secure Shell (SSH); however, you can use Linux's virtual terminal (VT) feature to log in multiple times with a single keyboard and monitor. Sometimes, you might want to know who is using the computer. Linux is modeled after Unix, which was designed as a multiuser OS. In principle, you can have thousands of accounts on a single Unix (or Linux) computer. At least one user, though, needs extraordinary power in order to manage the features of the computer as a whole.