As I wrote in http://superuser.com/a/293160/38062:
The problem here is the word "filesystem". In the POSIX/Unix/Linux worlds, it is used to mean several different things.
- The "filesystem" is sometimes the entire system of files, rooted at
/and as presented to applications softwares by the operating system kernel. With this meaning, people talk of POSIX operating systems having a "single filesystem tree", for example.
- A "filesystem" is sometimes one (or more) slice(s) of a (or several) DASD(s) — one or more collections of contiguous disc sectors formatted as a single volume with a given format — as demarcated by some disc partitioning scheme. With this meaning, people talk of, say, "formatting my
/usr" here is the (expected) mountpoint of the volume, or (in some partitioning schemes) its identifying label.
- A "filesystem" is sometimes an abstract joinable tree of files and directories, presented by a filesystem driver (i.e. the VFS layer) to the rest of the system. With this meaning, people talk of, say, "mounting the proc filesystem on
/proc" or "using a tmpfs filesystem for
You're seeing meaning #1 when you see "
/usr/bin filesystem". It's a filesystem tree rooted at the directory
/usr/bin. Yes, Linux very much does have the concept of directories.
Meaning #2 and meaning #3 are what you're mis-reading it as. People are not talking about
/usr/bin as an on-disc data set, demarcated by disc slicing/partitioning. Nor are they talking about
/usr/bin as a particular type of filesystem driver, or a particular disc volume format.
- Ramesh Bangia (2010). "file system". Dictionary of Information Technology. Laxmi Publications, Ltd. ISBN 9789380298153. p. 224.
- File System. "Base Definitions". The Open Group Base Specifications. Issue 7 IEEE 1003.1. The Open Group. 2013.
- Binh Nguyen (2004-08-16). "filesystem". The Linux Dictionary. Version 0.16. p. 616.