Basic User and Group Concepts

Linux is a truly multiuser operating system. The concept of users and groups in Linux is inherited from the Unix tradition, and among other things provides a very clear and precise distinction between what normal users can do and what a privileged user can do (such as the root user, the superuser and ultimate administrator on a Linux system, who can do anything). The fact that the system of users and groups and the associated system of permissions is built into the system at the deepest level is one of the reasons why Linux (and Unix in general) is fundamentally secure in a way that Microsoft Windows is not. Although modern versions of Windows have a similar concept of users and groups, Windows tends to trade security for usability, and the associated concept of the permissions with which a process can be run leaves a lot to be desired. This is why there are so many Windows vulnerabilities that are based on exploiting the scripting capabilities of programs that are run with user privileges but that turn out to be capable of subverting the system.

p : tj If you're interested in the differences between the major operating systems, Eric Ray-

t-v ^ i-.-.,". \'CV..\*: mond, noted open source guru and philosopher, offers some interesting comparisons and discussion at www.catb.org/~esr/writings/taoup/html/ch03s02.html.

Every Linux system has a number of user accounts: Some of these are human users, and some of them are system users, which are user identities that the system uses to perform certain tasks.

The users on a system (provided it does authentication locally) are listed in the file /etc/ passwd. Look at your own entry in /etc/passwd; it will look something like this:

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