Users and Groups

Every person who uses the system has an account on the system. To the system, they appear as different users. There are other users, too: usually each service that we provide (such as web, or mail) runs under its own user. Even though these users cannot log on in the usual way, the system treats them just the same.

Users are then placed in various groups: typically most users will just be a member of the users group, but a user can be in many groups. For example, committee members are also in the committee group; webteam members in the webteam group, and so on.

So who cares? The reason you need to know this is because each file on the system has associated with it an owner and a group. Each file is owned by some user. This is done so that different people have permission to do different things to a file: you might want it that only you can edit a page on your website, but that others can read it. The page needs to differentiate between you and everyone else, and it does that by being owned by you.

Next lets talk about the different kinds of permissions.