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In a computer
file system In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one lar ...
, and primarily used in the
Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...
and
Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...
operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
s, the root directory is the first or top-most directory in a hierarchy. It can be likened to the trunk of a
tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
, 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 Mount is often used as part of the name of specific mountains, e.g. Mount Everest. Mount or Mounts may also refer to: Places * Mount, Cornwall, a village in Warleggan parish, England * Mount, Perranzabuloe, a hamlet in Perranzabuloe parish, ...
as the system boots up.


Unix-like systems

Unix abstracts the nature of this tree hierarchy entirely and in Unix and Unix-like systems the root directory is denoted by the / (slash) sign. Though the root directory is conventionally referred to as /, the directory entry itself has no name its path is the "empty" part before the initial directory separator character (/). All file system entries, including mounted file systems are "branches" of this root.


chroot

In UNIX-like operating systems, each process has its own idea of what the root directory is. For most processes this is the same as the system's actual root directory, but it can be changed by calling the
system call In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, acc ...
. This is typically done to create a secluded environment to run software that requires legacy libraries and sometimes to simplify software installation and debugging. Chroot is not meant to be used for enhanced security as the processes inside can break out.


Super-root

Some Unix systems support a directory below the root directory. Normally, "/.." points back to the same inode as "/", however, under , this can be changed to point to a super-root directory, where remote trees can be mounted. If, for example, two workstations "pcs2a" and "pcs2b" were connected via "connectnodes" and "uunite" startup script, "/../pcs2b" could be used to access the root directory of "pcs2b" from "pcs2a".


Related uses

On many
Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...
es, there is also a directory named (pronounced "slash root"). This is the home directory of the 'root' superuser. On many
Macintosh The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and software en ...
and iOS systems this superuser home directory is .


See also

*
Filesystem Hierarchy Standard The Filesystem Hierarchy Standard (FHS) is a reference describing the conventions used for the layout of a UNIX system. It has been made popular by its use in Linux distributions, but it is used by other UNIX variants as well. It is maintained b ...
(FHS) * Parent directory *
Working directory In computing, the working directory of a process is a directory of a hierarchical file system, if any, dynamically associated with each process. It is sometimes called the current working directory (CWD), e.g. the BSD getcwd function, or just ...


References

{{Reflist File system directories