Anyone trying to access a UNIX system requires the correct login information, which is allocated by a system administrator. At login time, you are prompted to enter your login name, followed by your password; if this is correct, you will be allowed on the system. This process is carried out for a number of reasons, including the following:
It ensures that the system remains secure by only allowing users that know a login name and corresponding password to access the system.
It allows the administrator to determine who is logged on at any particular time and also how much time and/or space they are using.
It allows users to be gathered together into groups and assigned permissions as required.
While we often think of a user as being ...