What is Unix file system ?

The Unix file system has a hierarchical (or tree-like) structure with its highest level directory called root (denoted by /, pronounced slash). Immediately below the root level directory are several subdirectories, most of which contain system files. Below this can exist system files, application files, and/or user data files. Similar to the concept of the process parent-child relationship, all files on a Unix system are related to one another. That is, files also have a parent-child existence. Thus, all files (except one) share a common parental link, the top-most file (i.e. /) being the exception. Below is a diagram (slice) of a "typical" Unix file system. As you can see, the top-most directory is / (slash), with the directories directly beneath being system directories. Note that as Unix implementaions and vendors vary, so will this file system hierarchy. However, the organization of most file systems is similar.

While this diagram is not all inclusive, the following system files (i.e. directories) are present in most Unix filesystems:

 • bin - short for binaries, this is the directory where many commonly used executable commands reside 

• dev - contains device specific files 

• etc - contains system configuration files

 • home - contains user directories and files

 • lib - contains all library files

 • mnt - contains device files related to mounted devices 

• proc - contains files related to system processes 

• root - the root users' home directory (note this is different than /) 

• sbin - system binary files reside here. If there is no sbin directory on your system, these files most likely reside in etc 

• tmp - storage for temporary files which are periodically removed from the filesystem 

• usr - also contains executable commands