AFS Volume? Why do I care how loud my files are?

No, no, no; that's not what AFS volume means. In order to understand AFS, it is important to know some basic terminology. Following is a list of terms to provide you with some important background for when you use AFS:

Volume: An AFS volume is a collection of files and directories that are grouped together as one unit. A volume can be backed up, renamed, moved from one server to another, replicated, created, or destroyed as a unit.

User: A user is someone who is registered with AFS. You must be registered with AFS if you wish to be able to own files. The process of telling AFS who are you is called authentication.

Group: A group is a list of users. Currently, it is not possible for a group to contain other groups.

Cell: An AFS cell is essentially a domain of authority. It is currently the largest unit used in AFS. Each cell has a list of administrators, a list of users, a list of groups, and a list of volumes. Each of these lists is private to the cell. This means that an administrator in one cell may or may not have any access to another cell. A user in one cell may not even exist in another. A cell is also a domain of authentication. If you are the user qjb in the athena.mit.edu cell, you may not have any access at all to files belonging to a user named qjb in the andrew.cmu.edu cell. Likewise, someone who has administrative capabilities in the sipb.mit.edu cell may not be able to touch the athena.mit.edu cell.

ACL: ACL stands for Access Control List. When referring to access control lists, some people say the initials (``A-C-L'') and others pronounce the acronym (``ackle''). An access control list pairs users and groups with operations that they are allowed (or not allowed) to perform. Although access control lists are used for much more than just AFS, only AFS access control lists will be discussed here. A typical access control list would say something like, ``The user potato is allowed to create files in this directory. The user soup is allowed to modify existing files and create new files in this directory. Anyone else is allowed only to read files in this directory.'' AFS access control lists and how to use them are explained in more detail later in this document.