In a
computer file system, and primarily used in the
Unix and
Unix-like operating systems, the
root directory is the first or top-most
directory in a hierarchy. It can be likened to the trunk of a
tree, as the starting point where all branches originate from. The
root file system is the file system contained on the same
disk partition on which the root directory is located; it is the filesystem on top of which all other file systems are
mounted as the system
boots up.