Users are the primary agents on the system. Each user is required to log in to the system. The user supplies the user name of an account and a password if the account has one (on a secure system, all accounts either have passwords or are invalidated). If the password is correct, the user is logged in to that account; the user acquires the access rights and privileges of the account. The /etc/passwd and /etc/security/passwd files maintain user passwords.
Groups are collections of users who can share access permissions for protected resources. A group has an ID, and a group is composed of members and administrators. The creator of the group is usually the first administrator. There are three types of groups:
|User group||User groups ...|