Because this is not a general book about operating system principles, there are many OS-related terms described throughout the book that do not have full, descriptive definitions. This chapter provides a glossary of these terms and filesystem-related terms.

/proc. The process filesystem, also called the /proc filesystem, is a pseudo filesystem that displays to the user a hierarchical view of the processes running on the machine. There is a directory in the filesystem per user process with a whole host of information about each process. The /proc filesystem also provides the means to both trace running processes and debug another process.

ACL. Access Control Lists, or more commonly known as ACLs, provide an additional level of security on top of the traditional UNIX security model. An ACL is a list of users who are allowed access to a file along with the type of access that they are allowed.

address space. There are two main uses of the term address space. It can be used to refer to the addresses that a user process can access—this is where the user instructions, data, stack, libraries, and mapped files would reside. One user address space is protected from another user through use of hardware mechanisms. The other use for the term is to describe the instructions, data, and stack areas of the kernel. There is typically only one kernel address space that is protected from user processes.

AFS. The Andrew File System (AFS) is a distributed filesystem developed at CMU as part ...

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