Chapter 27. Basic UNIX System Concepts (Web site construction)
Chapter 27. Basic UNIX System Concepts The name UNIX may be familiar to you. You may even use a UNIX system at work, in which case this chapter may be of less interest. For those of you who have never used a UNIX system, reading this chapter is absolutely necessary. Understanding the concepts which will be introduced here will answer a surprisingly large number of questions commonly asked by beginners in the GNU/Linux world. Similarly some of these concepts will likely help you solve many of the problems you may encounter in the future. 1. Users and Groups Since they have a direct influence on all other concepts, this section will introduce the concepts of users and groups which are extremely important. Linux is a true multiuser system, and in order to use your GNU/Linux machine, you must have an account on the machine. When you created a user during installation, you actually created an account. In case you don’t remember, you were prompted for the following items: the user’s real name (which could actually be whatever you want); a login name; and a password. The two most important parameters here are the login name (commonly abbreviated to login) and the password. You must have both of these in order to access the system. When you create a user, a default group is also created. Later on, we will see that groups are useful when you want to share files with other people. A group may contain as many users as you wish, and it is very common to see such a separation in large systems. For example, at a university, you could have one group per department, another group for teachers, and so on. The opposite is also true: a user may be a member of one or more groups. A math teacher, for example, could be a member of the teachers’ group and also of his math students’ group. Now that we’ve covered the background information, let us look at how to actually log in. If the graphical interface is automatically started on boot up, your start-up screen will look like Figure 27.1, Graphical Mode Login Session [382].