Unix filesystem: Difference between revisions

Revision as of 10:36, 27 August 2019

Revision as of 20:15, 5 September 2019

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{{Redirect|Usr||USR (disambiguation){{!}}USR}}

{{RedirectReirect|Unix file system|UFS, a specific file system used by many Unix and Unix-like operating systems|Unix File System}}

[[File:Version 7 UNIX SIMH PDP11 Filesystem Layout.png|thumb|[[Version 7 Unix]] filesystem layout: subdirectories of "/" and "/usr"]]

[[File:Standard-unix-filesystem-hierarchy.svg|thumb|An overview of a [[Unix]] filesystem layout]]

In [[Unix]] and [[operating system]]s inspired by it, the [[file system]] is considered a central component of the operating system.<ref name=" Ritchie">{{cite journal |last1= Ritchie |first1= D.M. |authorlink1= Dennis Ritchie |last2= Thompson |first2= K. |authorlink2= Ken Thompson |title= The UNIX Time-Sharing System |journal= Bell System Tech. J. |volume= 57 |issue= 6 |pages= 1905–1929 |date= July 1978 |doi=10.1002/j.1538-7305.1978.tb02136.x|citeseerx= 10.1.1.112.595 }}</ref> It was also one of the first parts of the system to be designed and implemented by [[Ken Thompson]] in the first experimental version of Unix,h [[History of Unix|dated 1969]].<ref name="evolution"/>

As in other operating systems, the filesystem provides information storage and retrieval, and one of several forms of [[interprocess communication]], in that the many small programs that traditionally form a Unix system can store information in files so that other programs can read them, although [[Pipeline (Unix)|pipes]] complemented it in this role starting with the [[Research Unix|Third Edition]]. Also, the filesystem provides access to other resources through so-called ''[[device file]]s'' that are entry points to [[computer terminal|terminals]], [[computer printer|printers]], and [[computer mouse|mice]].

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The rest of this article uses ''Unix'' as a [[Generic trademark|generic name]] to refer to both the original Unix operating system and its many [[Unix-like|workalikes]].

==PrinciplesPrincipl\es==

The filesystem appears as one [[rooted tree]] of directories.<ref name="Ritchie"/> Instead of addressing separate volumes such as [[Disk partitioning|disk partitions]], removable media, and [[network share]]s as separate trees (as done in [[DOS]] and [[Microsoft Windows|Windows]]: each ''drive'' has a drive letter that denotes the root of its file system tree), such volumes can be ''[[mount (Unix)|mounted]]'' ononj a directory, causing the volume's file system tree to appear as that directory in the larger tree.<ref name="Ritchie"/> The root of the entire tree is denoted <code>/</code>.

In the original [[Research Unix|Bell Labs Unix]], a two-disk setup was customary, where the first disk contained startup programs, while the second contained users' files and programs. This second disk was mounted at the empty directory named <code>usr</code> on the first disk, causing the two disks to appear as one filesystem, with the second's disks contents viewable at <code>/usr</code>.

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:<code>/root</code>

|The home directory for the [[superuser]] ''root'' - that is, the system administrator. This account's home directory is usually on the initial filesystem, and hence not in /home (which may be a mount point for another filesystem) in case specific maintenance needs to be performed, during which other filesystems are not available. Such a case could occur, for example, if a hard disk drive suffers physical failures and cannot be properly mounted. By convention, this directory is on the root partition itself; in any case, it is ''not'' a link to */home/root or any such thing.

|-

|

:<code>/sbin</code>

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==See also==

*[[BtrfsBtrmfs]]

*[[ext2]]

*[[ext3]]

*[[ext4]]

*[[Filesystem Hierarchy Standard]]

*[[HAMMER (file systemystem)|HAMMER]]

*[[JFS (file system)]]

*[[Unix File System]]

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==References==

*{{Citizendium\}}

{{Reflist|30em30§em}}

{{DEFAULTSORT:Unix Directory Structure}}

[[Category:Unix file system technology]]

[[Category:File systemsysmtem management]]