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Encyclopedia > File system

In computing, a file system (often also written as filesystem) is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. File systems may use a data storage device such as a hard disk or CD-ROM and involve maintaining the physical location of the files, they might provide access to data on a file server by acting as clients for a network protocol (e.g., NFS, SMB, or 9P clients), or they may be virtual and exist only as an access method for virtual data (e.g., procfs). Image File history File links Mergefrom. ... It has been suggested that this article or section be merged into File_system#Types_of_file_systems. ... Library classification forms part of the field of library and information science. ... For the formal concept of computation, see computation. ... This article is about computer files and file systems in general terms. ... Many different consumer electronic devices can store data. ... Typical hard drives of the mid-1990s. ... The CD-ROM (an abbreviation for Compact Disc Read-Only Memory (ROM)) is a non-volatile optical data storage medium using the same physical format as audio compact discs, readable by a computer with a CD-ROM drive. ... Network File System (NFS) is a network file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network as easily as if the network devices were attached to its local disks. ... In computer networking, Server Message Block (SMB) operates as an application-level network protocol mainly applied to shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. ... 9P, or the Plan 9 Filesystem Protocol, is a network protocol developed for the Plan 9 distributed operating system as the means of connecting the components of a Plan 9 system (site). ... On Unix-like computer systems, procfs is short for process filesystem: a pseudo-filesystem which is used to access kernel information about processes. ...


More formally, a file system is a set of abstract data types that are implemented for the storage, hierarchical organization, manipulation, navigation, access, and retrieval of data. File systems share much in common with database technology, but it is debatable whether a file system can be classified as a special-purpose database (DBMS).[citation needed] In computing, an abstract data type (ADT) is a specification of a set of data and the set of operations that can be performed on the data. ... For other uses, see Data (disambiguation). ... A database management system (DBMS) is computer software designed for the purpose of managing databases. ...

Contents

Aspects of file systems

The most familiar file systems make use of an underlying data storage device that offers access to an array of fixed-size blocks, sometimes called sector, generally 512 bytes each. The file system software is responsible for organizing these sectors into files and directories, and keeping track of which sectors belong to which file and which are not being used. Most file systems address data in fixed-sized units called "clusters" or "blocks" which contain a certain number of disk sectors (usually 1-64). This is the smallest logical amount of disk space that can be allocated to hold a file. Many different consumer electronic devices can store data. ... In computing (specifically data transmission and data storage), block size indicates a nominal size, usually expressed in bytes or bits, of a block of data. ... This article is about computer files and file systems in general terms. ... In computing, a directory, catalog, or folder, is an entity in a file system which can contain a group of files and/or other directories. ... In certain filesystem types like the File Allocation Table (FAT) filesystem of MS-DOS or the NTFS filesystem of Windows NT, a cluster is the unit of disk space allocation for files and directories. ... In computing (specifically data transmission and data storage), block size indicates a nominal size, usually expressed in bytes or bits, of a block of data. ... In the context of computer hardware, a sector is a sub-division of a track on a magnetic disk or optical disc. ...


However, file systems need not make use of a storage device at all. A file system can be used to organize and represent access to any data, whether it be stored or dynamically generated (eg, from a network connection).


Whether the file system has an underlying storage device or not, file systems typically have directories which associate file names with files, usually by connecting the file name to an index into a file allocation table of some sort, such as the FAT in an MS-DOS file system, or an inode in a Unix-like file system. Directory structures may be flat, or allow hierarchies where directories may contain subdirectories. In some file systems, file names are structured, with special syntax for filename extensions and version numbers. In others, file names are simple strings, and per-file metadata is stored elsewhere. A filename is a special kind of string used to uniquely identify a file stored on the file system of a computer. ... File Allocation Table (FAT) is a partially patented file system developed by Microsoft for MS-DOS and was the primary file system for consumer versions of Microsoft Windows up to and including Windows Me. ... File Allocation Table (FAT) is a partially patented file system developed by Microsoft for MS-DOS and was the primary file system for consumer versions of Microsoft Windows up to and including Windows Me. ... Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... In computing, an inode is a data structure on a traditional Unix-style file system such as UFS. An inode stores basic information about a regular file, directory, or other file system object. ... Diagram of the relationships between several Unix-like systems A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification. ... A filename extension is a suffix to the name of a computer file applied to indicate its type. ... Metadata is data about data. ...


Other bookkeeping information is typically associated with each file within a file system. The length of the data contained in a file may be stored as the number of blocks allocated for the file or as an exact byte count. The time that the file was last modified may be stored as the file's timestamp. Some file systems also store the file creation time, the time it was last accessed, and the time that the file's meta-data was changed. (Note that many early PC operating systems did not keep track of file times.) Other information can include the file's device type (e.g., block, character, socket, subdirectory, etc.), its owner user-ID and group-ID, and its access permission settings (e.g., whether the file is read-only, executable, etc.). This page is a candidate to be copied to Wiktionary. ... For the computer industry magazine, see Byte (magazine). ... In computer science and computer programming, system time represents a computer systems notion of the passing of time. ... A stylised illustration of a modern personal computer A personal computer (PC) is a computer whose original sales price, size, and capabilities make it useful for individuals. ... A device file or special file is an interface for a device driver that appears in a file system as if it were an ordinary file. ... In computing (specifically data transmission and data storage), block size indicates a nominal size, usually expressed in bytes or bits, of a block of data. ... An Internet socket (or commonly, a socket or network socket), is a communication end-point unique to a machine communicating on an Internet Protocol-based network, such as the Internet. ... This article is about the computing term. ... User in a computing context refers to one who uses a computer system. ... In computing, the term group generally refers to a grouping of users. ... Most modern file systems have methods of administering permissions or access rights to specific users and groups of users. ...


The hierarchical file system was an early research interest of Dennis Ritchie of Unix fame; previous implementations were restricted to only a few levels, notably the IBM implementations, even of their early databases like IMS. After the success of Unix, Ritchie extended the file system concept to every object in his later operating system developments, such as Plan 9 and Inferno. Dennis Ritchie Dennis MacAlistair Ritchie (born September 9, 1941) is a computer scientist notable for his influence on ALTRAN, B, BCPL, C, Multics, and Unix. ... Plan 9 from Bell Labs is a distributed operating system, primarily used as a research vehicle. ... Inferno is an operating system for creating and supporting distributed services. ...


Traditional file systems offer facilities to create, move and delete both files and directories. They lack facilities to create additional links to a directory (hard links in Unix), rename parent links (".." in Unix-like OS), and create bidirectional links to files. In computing, a hard link is a reference, or pointer, to physical data on a storage volume. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®, sometimes also written as or ® with small caps) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... Diagram of the relationships between several Unix-like systems A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification. ...


Traditional file systems also offer facilities to truncate, append to, create, move, delete and in-place modify files. They do not offer facilities to prepend to or truncate from the beginning of a file, let alone arbitrary insertion into or deletion from a file. The operations provided are highly asymmetric and lack the generality to be useful in unexpected contexts. For example, interprocess pipes in Unix have to be implemented outside of the file system because the pipes concept does not offer truncation from the beginning of files. A pipeline of three programs run on a text terminal In Unix-like computer operating systems, a pipeline is the original software pipeline: a set of processes chained by their standard streams, so that the output of each process (stdout) feeds directly as input (stdin) of the next one. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®, sometimes also written as or ® with small caps) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ... In mathematics, truncation is the term used for reducing the number of digits right of the decimal point, by discarding the least significant ones. ...


Secure access to basic file system operations can be based on a scheme of access control lists or capabilities. Research has shown access control lists to be difficult to secure properly, which is why research operating systems tend to use capabilities. Commercial file systems still use access control lists. see: secure computing In computer security, an access control list (ACL) is a list of permissions attached to an object. ... A capability (also known as a key) is a concept in secure computing. ... Secure Computing Corporation, or SCC, is a public company (NASDAQ: SCUR) that develops and sells computer security products, such as: Network Gateway Security Solutions including Sidewinder, and SnapGear Messaging Gateway Security Solutions including IronMail Email Security , IronIM IM Security Appliance, IronNet Policy/Compliance Security Appliance, Edge Perimeter Email Security Appliances...


Arbitrary attributes can be associated on advanced file systems, such as XFS, ext2/ext3, some versions of UFS, and HFS+, using extended file attributes. This feature is implemented in the kernels of Linux, FreeBSD and Mac OS X operating systems, and allows metadata to be associated with the file at the file system level. This, for example, could be the author of a document, the character encoding of a plain-text document, or a checksum. XFS is a high-performance journaling file system created by Silicon Graphics for their IRIX operating system. ... The ext2 or second extended file system is a file system for the Linux kernel. ... The ext3 or third extended filesystem is a journalled file system that is commonly used by the Linux operating system. ... The UNIX file system (UFS) is a file system used by many Unix and Unix-like operating systems. ... HFS Plus or HFS+ is a file system developed by Apple Computer to replace their Hierarchical File System (HFS) as the primary file system used on Macintosh computers. ... Extended file attributes is a file system feature that enables users to associate computer files with metadata not interpreted by the filesystem, whereas regular attributes have a purpose strictly defined by the filesystem (such as permissions or records of creation and modification times). ... The Linux kernel is a Unix-like operating system kernel. ... FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4. ... Mac OS X (pronounced ) is a line of graphical operating systems developed, marketed, and sold by Apple Inc. ...


Types of file systems

File system types can be classified into disk file systems, network file systems and special purpose file systems.


Disk file systems

A disk file system is a file system designed for the storage of files on a data storage device, most commonly a disk drive, which might be directly or indirectly connected to the computer. Examples of disk file systems include FAT, FAT32, NTFS, HFS and HFS+, ext2, ext3, ISO 9660, ODS-5, and UDF. Some disk file systems are journaling file systems or versioning file systems. This article is about computer files and file systems in general terms. ... Many different consumer electronic devices can store data. ... Disk Drive is the afternoon show on CBC Radio Two. ... File Allocation Table (FAT) is a partially patented file system developed by Microsoft for MS-DOS and was the primary file system for consumer versions of Microsoft Windows up to and including Windows Me. ... File Allocation Table (FAT) is a file system that was developed for MS-DOS and used in consumer versions of Microsoft Windows up to and including Windows Me. ... NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, and Windows Vista. ... Hierarchical File System (HFS), is a file system developed by Apple Computer for use on computers running Mac OS. Originally designed for use on floppy and hard disks, it can also be found on read-only media such as CD-ROMs. ... HFS Plus or HFS+ is a file system developed by Apple Computer to replace their Hierarchical File System (HFS) as the primary file system used on Macintosh computers. ... The ext2 or second extended file system is a file system for the Linux kernel. ... The ext3 or third extended filesystem is a journalled file system that is commonly used by the Linux operating system. ... ISO 9660, a standard published by the International Organization for Standardization, defines a file system for CD-ROM media. ... Files-11, also known as on-disk structure, is the filesystem used by Hewlett-Packards OpenVMS operating system, and also (in a simpler form) by the older RSX-11. ... The Universal Disk Format (UDF) is a format specification of a file system for storing files on optical media. ... A journaling (or journalling) file system is a file system that logs changes to a journal (usually a circular log in a specially-allocated area) before actually writing them to the main file system. ... A versioning file system is a file system which provides for the concurrent existence of several versions of a file. ...


Flash file systems

A flash file system is a file system designed for storing files on flash memory devices. These are becoming more prevalent as the number of mobile devices is increasing, and the capacity of flash memories catches up with hard drives. This article is about computer files and file systems in general terms. ... A USB flash drive. ...


While a block device layer can emulate a disk drive so that a disk file system can be used on a flash device, this is suboptimal for several reasons: In computing (specifically data transmission and data storage), block size indicates a nominal size, usually expressed in bytes or bits, of a block of data. ...

  • Erasing blocks: Flash memory blocks have to be explicitly erased before they can be written to. The time taken to erase blocks can be significant, thus it is beneficial to erase unused blocks while the device is idle.
  • Random access: Disk file systems are optimized to avoid disk seeks whenever possible, due to the high cost of seeking. Flash memory devices impose no seek latency.
  • Wear levelling: Flash memory devices tend to wear out when a single block is repeatedly overwritten; flash file systems are designed to spread out writes evenly.

Log-structured file systems have all the desirable properties for a flash file system. Such file systems include JFFS2 and YAFFS. In computer science, random access is the ability to access a random element of a group in equal time. ... Seek time is one of the several delays associated with reading or writing data on a computers disk drive, and somewhat similar for CD or DVD drives. ... Wear levelling (also written -levelling) is a technique for prolonging the service life of some kinds of eraseable computer storage media, e. ... The Log-Structured File System (or LFS) is an implementation of a log-structured file system, originally developed for BSD. It was removed from FreeBSD and OpenBSD. In NetBSD, its still present, but it appears to be no longer completely functional as of NetBSD 2. ... The Journalling Flash File System version 2 or JFFS2 is a log-structured file system for use in flash memory devices. ... This article needs to be cleaned up to conform to a higher standard of quality. ...


Database file systems

A new concept for file management is the concept of a database-based file system. Instead of, or in addition to, hierarchical structured management, files are identified by their characteristics, like type of file, topic, author, or similar metadata. Example: dbfs. Metadata is data about data. ...


Transactional file systems

Each disk operation may involve changes to a number of different files and disk structures. In many cases, these changes are related, meaning that it is important that they all be executed at the same time. Take for example a bank sending another bank some money electronically. The bank's computer will "send" the transfer instruction to the other bank and also update its own records to indicate the transfer has occurred. If for some reason the computer crashes before it has had a chance to update its own records, then on reset, there will be no record of the transfer but the bank will be missing some money.


Transaction processing introduces the guarantee that at any point while it is running, a transaction can either be finished completely or reverted completely (though not necessarily both at any given point). This means that if there is a crash or power failure, after recovery, the stored state will be consistent. (Either the money will be transferred or it will not be transferred, but it won't ever go missing "in transit".) In computer science, transaction processing is information processing that is divided into individual, indivisible operations, called Each transaction must succeed or fail as a complete unit; it cannot remain in an intermediate state. ...


This type of file system is designed to be fault tolerant, but may incur additional overhead to do so.


Journaling file systems are one technique used to introduce transaction-level consistency to filesystem structures. A journaling (or journalling) file system is a file system that logs changes to a journal (usually a circular log in a specially-allocated area) before actually writing them to the main file system. ...


Network file systems

Main article: Network file system

A network file system is a file system that acts as a client for a remote file access protocol, providing access to files on a server. Examples of network file systems include clients for the NFS, SMB protocols, and file-system-like clients for FTP and WebDAV. For the protocol of this name, see Network File System (protocol). ... Network File System (NFS) is a network file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network as easily as if the network devices were attached to its local disks. ... In computer networking, Server Message Block (SMB) operates as an application-level network protocol mainly applied to shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. ... This article is about the File Transfer Protocol standardised by the IETF. For other file transfer protocols, see File transfer protocol (disambiguation). ... WebDAV, an abbreviation that stands for Web-based Distributed Authoring and Versioning, refers to the set of extensions to the Hypertext Transfer Protocol (HTTP) which allows users to collaboratively edit and manage files on remote World Wide Web servers. ...


Special purpose file systems

A special purpose file system is basically any file system that is not a disk file system or network file system. This includes systems where the files are arranged dynamically by software, intended for such purposes as communication between computer processes or temporary file space. This article is about computer files and file systems in general terms. ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ... In computing, a process is, roughly speaking, a task being run by a computer, often simultaneously with many other tasks. ...


Special purpose file systems are most commonly used by file-centric operating systems such as Unix. Examples include the procfs (/proc) file system used by some Unix variants, which grants access to information about processes and other operating system features. On Unix-like computer systems, procfs is short for process filesystem: a pseudo-filesystem which is used to access kernel information about processes. ... In computing, a process is an instance of a computer program that is being executed. ...


Deep space science exploration craft, like Voyager I & II used digital tape based special file systems. Most modern space exploration craft like Cassini-Huygens used Real-time operating system file systems or RTOS influenced file systems. The Mars Rovers are one such example of an RTOS file system, important in this case because they are implemented in flash memory. Categories: Jupiter | Saturn | NASA probes | Astronomy stubs ... Categories: Jupiter | Saturn | Uranus | Neptune | NASA probes | Astronomy stubs ... Cassini-Huygens is a joint NASA/ESA/ASI unmanned space mission intended to study Saturn and its moons. ... A real-time operating system (RTOS) is a multitasking operating system intended for real-time applications. ... A Mars Rover is an unmanned land vehicle for exploration of the planet Mars. ...


File systems and operating systems

Most operating systems provide a file system, as a file system is an integral part of any modern operating system. Early microcomputer operating systems' only real task was file management — a fact reflected in their names (see DOS). Some early operating systems had a separate component for handling file systems which was called a disk operating system. On some microcomputers, the disk operating system was loaded separately from the rest of the operating system. On early operating systems, there was usually support for only one, native, unnamed file system; for example, CP/M supports only its own file system, which might be called "CP/M file system" if needed, but which didn't bear any official name at all. An operating system (OS) is the software that manages the sharing of the resources of a computer and provides programmers with an interface used to access those resources. ... The Commodore 64 was one of the most popular microcomputers of its era, and is the best selling model of home computer of all time. ... This article is about the family of closely related operating systems for the IBM PC compatible platform. ... Disk Operating System (specifically) and disk operating system (generically), most often abbreviated as DOS (not to be confused with the DOS family of disk operating systems for the IBM PC compatible platform), refer to operating system software used in most computers that provides the abstraction and management of secondary storage... CP/M is an operating system originally created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc. ...


Because of this, there needs to be an interface provided by the operating system software between the user and the file system. This interface can be textual (such as provided by a command line interface, such as the Unix shell, or OpenVMS DCL) or graphical (such as provided by a graphical user interface, such as file browsers). If graphical, the metaphor of the folder, containing documents, other files, and nested folders is often used (see also: directory and folder). This article or section does not adequately cite its references or sources. ... Screenshot of a sample Bash session, taken on Gentoo Linux. ... DCL is the standard Command line interface (CLI) adopted by most of the operating systems that were sold by the former Digital Equipment Corporation (which has since been acquired by Hewlett-Packard). ... GUI redirects here. ... A file manager is a software tool that provides a user interface to work with computer files. ... Look up Folder in Wiktionary, the free dictionary. ... In computing, a directory, catalog, or folder, is an entity in a file system which can contain a group of files and/or other directories. ... Look up Folder in Wiktionary, the free dictionary. ...


Flat file systems

In a flat file system, there are no subdirectories—everything is stored at the same (root) level on the media, be it a hard disk, floppy disk, etc. While simple, this system rapidly becomes inefficient as the number of files grows, and makes it difficult for users to organise data into related groups. In computing, a directory, catalog, or folder, is an entity in a file system which can contain a group of files and/or other directories. ... In computer file systems, the root directory is the first or top-most directory in a hierarchy. ... Typical hard drives of the mid-1990s. ... A floppy disk is a data storage device that is composed of a disk of thin, flexible (floppy) magnetic storage medium encased in a square or rectangular plastic shell. ...


Like many small systems before it, the original Apple Macintosh featured a flat file system, called Macintosh File System. Its version of Mac OS was unusual in that the file management software (Macintosh Finder) created the illusion of a partially hierarchical filing system on top of MFS. This structure meant that every file on a disk had to have a unique name, even if it appeared to be in a separate folder. MFS was quickly replaced with Hierarchical File System, which supported real directories. The first Macintosh computer, introduced in 1984, upgraded to a 512K Fat Mac. The Macintosh or Mac, is a line of personal computers designed, developed, manufactured, and marketed by Apple Computer. ... This article is about the MFS file system. ... This article relates to both the original Classic Mac OS as well as Mac OS X, Apples more recent operating system. ... The Finder is the default application program used on the Mac OS and Mac OS X operating systems that is responsible for the overall user-management of files, disks, network volumes and the launching of other applications. ... Hierarchical File System (HFS), is a file system developed by Apple Computer for use on computers running Mac OS. Originally designed for use on floppy and hard disks, it can also be found on read-only media such as CD-ROMs. ... In computing, a directory, catalog, or folder, is an entity in a file system which can contain a group of files and/or other directories. ...


File systems under Unix-like operating systems

Wikibooks
Wikibooks Guide to Unix has a page on the topic of

Unix-like operating systems create a virtual file system, which makes all the files on all the devices appear to exist in a single hierarchy. This means, in those systems, there is one root directory, and every file existing on the system is located under it somewhere. Furthermore, the root directory does not have to be in any physical place. It might not be on your first hard drive - it might not even be on your computer. Unix-like systems can use a network shared resource as its root directory. Image File history File links Wikibooks-logo-en. ... Wikibooks logo Wikibooks, previously called Wikimedia Free Textbook Project and Wikimedia-Textbooks, is a wiki for the creation of books. ... Diagram of the relationships between several Unix-like systems A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification. ... In computer file systems, the root directory is the first or top-most directory in a hierarchy. ...


Unix-like systems assign a device name to each device, but this is not how the files on that device are accessed. Instead, to gain access to files on another device, you must first inform the operating system where in the directory tree you would like those files to appear. This process is called mounting a file system. For example, to access the files on a CD-ROM, one must tell the operating system "Take the file system from this CD-ROM and make it appear under such-and-such directory". The directory given to the operating system is called the mount point - it might, for example, be /media. The /media directory exists on many Unix systems (as specified in the Filesystem Hierarchy Standard) and is intended specifically for use as a mount point for removable media such as CDs, DVDs and like floppy disks. It may be empty, or it may contain subdirectories for mounting individual devices. Generally, only the administrator (i.e. root user) may authorize the mounting of file systems. Mounting, in computer science, is the process of making a file system ready for use by the operating system, typically by reading certain index data structures from storage into memory ahead of time. ... The CD-ROM (an abbreviation for Compact Disc Read-Only Memory (ROM)) is a non-volatile optical data storage medium using the same physical format as audio compact discs, readable by a computer with a CD-ROM drive. ... A mount point is a term used to describe where the computer puts the files in a file system on Unix-like systems. ... The Filesystem Hierarchy Standard (FHS) defines the main directories and their contents in Linux and other Unix-like computer operating systems. ... A system administrator, or sysadmin, is a person employed to maintain, and operate a computer system or network. ... The superuser is the term for the system administrator on many computer operating systems. ...


Unix-like operating systems often include software and tools that assist in the mounting process and provide it new functionality. Some of these strategies have been coined "auto-mounting" as a reflection of their purpose. Diagram of the relationships between several Unix-like systems A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification. ...

  1. In many situations, file systems other than the root need to be available as soon as the operating system has booted. All Unix-like systems therefore provide a facility for mounting file systems at boot time. System administrators define these file systems in the configuration file fstab, which also indicates options and mount points.
  2. In some situations, there is no need to mount certain file systems at boot time, although their use may be desired thereafter. There are some utilities for Unix-like systems that allow the mounting of predefined file systems upon demand.
  3. Removable media have become very common with microcomputer platforms. They allow programs and data to be transferred between machines without a physical connection. Common examples include USB flash drives, CD-ROMs and DVDs. Utilities have therefore been developed to detect the presence and availability of a medium and then mount that medium without any user intervention.
  4. Progressive Unix-like systems have also introduced a concept called supermounting; see, for example, the Linux supermount-ng project. For example, a floppy disk that has been supermounted can be physically removed from the system. Under normal circumstances, the disk should have been synchronised and then unmounted before its removal. Provided synchronisation has occurred, a different disk can be inserted into the drive. The system automatically notices that the disk has changed and updates the mount point contents to reflect the new medium. Similar functionality is found on standard Windows machines.
  5. A similar innovation preferred by some users is the use of autofs, a system that, like supermounting, eliminates the need for manual mounting commands. The difference from supermount, other than compatibility in an apparent greater range of applications such as access to file systems on network servers, is that devices are mounted transparently when requests to their file systems are made, as would be appropriate for file systems on network servers, rather than relying on events such as the insertion of media, as would be appropriate for removable media.

In computing, booting (booting up) is a bootstrapping process that starts operating systems when the user turns on a computer system. ... A system administrator, or sysadmin, is a person employed to maintain, and operate a computer system or network. ... The fstab (for file systems table) file is commonly found on Unix and Unix-like systems and is part of the system configuration. ... In computing, booting (booting up) is a bootstrapping process that starts operating systems when the user turns on a computer system. ... The Commodore 64 was one of the most popular microcomputers of its era, and is the best selling model of home computer of all time. ... JumpDrive redirects here. ... The CD-ROM (an abbreviation for Compact Disc Read-Only Memory (ROM)) is a non-volatile optical data storage medium using the same physical format as audio compact discs, readable by a computer with a CD-ROM drive. ... DVD (also known as Digital Versatile Disc or Digital Video Disc) is a popular optical disc storage media format. ... For other uses, see Distributed file system (disambiguation). ...

File systems under Mac OS X

Mac OS X uses a file system that it inherited from classic Mac OS called HFS Plus. HFS Plus is a metadata-rich and case preserving file system. Due to the Unix roots of Mac OS X, Unix permissions were added to HFS Plus. Later versions of HFS Plus added journaling to prevent corruption of the file system structure and introduced a number of optimizations to the allocation algorithms in an attempt to defragment files automatically without requiring an external defragmenter. Mac OS X (pronounced ) is a line of graphical operating systems developed, marketed, and sold by Apple Inc. ... This article relates to both the original Classic Mac OS as well as Mac OS X, Apples more recent operating system. ... HFS Plus or HFS+ is a file system developed by Apple Computer to replace their Hierarchical File System (HFS) as the primary file system used on Macintosh computers. ... Metadata is data about data. ... When a computer stores text, the computer may keep or discard case information. ... A journaling (or journalling) file system is a file system that logs changes to a journal (usually a circular log in a specially-allocated area) before actually writing them to the main file system. ...


Filenames can be up to 255 characters. HFS Plus uses Unicode to store filenames. On Mac OS X, the filetype can come from the type code, stored in file's metadata, or the filename. The Unicode Standard, Version 5. ... A file format is a particular way to encode information for storage in a computer file. ... A type code is a mechanism used in pre-Mac OS X versions of the Macintosh operating system to denote a files format, in a manner similar to file extensions in other operating systems. ...


HFS Plus has three kinds of links: Unix-style hard links, Unix-style symbolic links and aliases. Aliases are designed to maintain a link to their original file even if they are moved or renamed; they are not interpreted by the file system itself, but by the File Manager code in userland. In computing, a hard link is a reference, or pointer, to physical data on a storage volume. ... In computing, a symbolic link (often shortened to symlink and also known as a soft link) consists of a special type of file that serves as a reference to another file. ... In System 7 and later, an alias is a small file that represents another object in the file system. ... For information on the company called UserLand, see UserLand Software. ...


Mac OS X also supports the UFS file system, derived from the BSD Unix Fast File System via NeXTSTEP. The UNIX file system (UFS) is a file system used by many Unix and Unix-like operating systems. ... BSD redirects here; for other uses see BSD (disambiguation). ... NEXTSTEP is the original object-oriented, multitasking operating system that NeXT Computer, Inc. ...


File systems under Plan 9 from Bell Labs

Plan 9 from Bell Labs was originally designed to extend some of Unix's good points, and to introduce some new ideas of its own while fixing the shortcomings of Unix. Plan 9 from Bell Labs is a distributed operating system, primarily used as a research vehicle. ...


With respect to file systems, the Unix system of treating things as files was continued, but in Plan 9, everything is treated as a file, and accessed as a file would be (i.e., no ioctl or mmap). Perhaps surprisingly, while the file interface is made universal it is also simplified considerably, for example symlinks, hard links and suid are made obsolete, and an atomic create/open operation is introduced. More importantly the set of file operations becomes well defined and subversions of this like ioctl are eliminated. In computing, the system call ioctl (IPA: ), found on Unix-like systems, allows an application to control or communicate with a device driver outside the usual read/write of data. ... In computing, mmap() is a POSIX-compliant Unix system call that maps files or devices into memory. ...


Secondly, the underlying 9P protocol was used to remove the difference between local and remote files (except for a possible difference in latency). This has the advantage that a device or devices, represented by files, on a remote computer could be used as though it were the local computer's own device(s). This means that under Plan 9, multiple file servers provide access to devices, classing them as file systems. Servers for "synthetic" file systems can also run in user space bringing many of the advantages of micro kernel systems while maintaining the simplicity of the system. 9P, or the Plan 9 Filesystem Protocol, is a network protocol developed for the Plan 9 distributed operating system as the means of connecting the components of a Plan 9 system (site). ... For other uses, see Lag (disambiguation). ...


Everything on a Plan 9 system has an abstraction as a file; networking, graphics, debugging, authentication, capabilities, encryption, and other services are accessed via I-O operations on file descriptors. For example, this allows the use of the IP stack of a gateway machine without need of NAT, or provides a network-transparent window system without the need of any extra code.


Another example: a Plan-9 application receives FTP service by opening an FTP site. The ftpfs server handles the open by essentially mounting the remote FTP site as part of the local file system. With ftpfs as an intermediary, the application can now use the usual file-system operations to access the FTP site as if it were part of the local file system. A further example is the mail system which uses file servers that synthesize virtual files and directories to represent a user mailbox as /mail/fs/mbox. The wikifs provides a file system interface to a wiki. This article is about the File Transfer Protocol standardised by the IETF. For other file transfer protocols, see File transfer protocol (disambiguation). ... Wikifs is a wiki file system for the Plan 9 operating system. ...


These file systems are organized with the help of private, per-process namespaces, allowing each process to have a different view of the many file systems that provide resources in a distributed system.


The Inferno operating system shares these concepts with Plan 9. Inferno is an operating system for creating and supporting distributed services. ...


File systems under Microsoft Windows

Windows makes use of the FAT and NTFS (New Technology File System) file systems. NTFS is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, and Windows Vista. ...


The FAT (File Allocation Table) filing system, supported by all versions of Microsoft Windows, was an evolution of that used in Microsoft's earlier operating system (MS-DOS which in turn was based on 86-DOS). FAT ultimately traces its roots back to the shortlived M-DOS project and Standalone disk BASIC before it. Over the years various features have been added to it, inspired by similar features found on file systems used by operating systems such as Unix. File Allocation Table (FAT) is a partially patented file system developed by Microsoft for MS-DOS and was the primary file system for consumer versions of Microsoft Windows up to and including Windows Me. ... Windows redirects here. ... Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ... 86-DOS was an operating system developed and marketed by Seattle Computer Products for its Intel 8086-based computer kit. ... Microsoft BASIC is the foundation product of the Microsoft company. ... Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®, sometimes also written as or ® with small caps) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ...


Older versions of the FAT file system (FAT12 and FAT16) had file name length limits, a limit on the number of entries in the root directory of the file system and had restrictions on the maximum size of FAT-formatted disks or partitions. Specifically, FAT12 and FAT16 had a limit of 8 characters for the file name, and 3 characters for the extension. This is commonly referred to as the 8.3 filename limit. VFAT, which was an extension to FAT12 and FAT16 introduced in Windows NT 3.5 and subsequently included in Windows 95, allowed long file names (LFN). FAT32 also addressed many of the limits in FAT12 and FAT16, but remains limited compared to NTFS. In computer engineering, hard disk drive partitioning is the creation of logical divisions upon a hard disk that allows one to apply operating system-specific logical formatting. ... A 8. ... Windows NT 3. ... Long filename is the name given to the longer and therefore more descriptive titles on the FAT filesystem, which was previously restricted to eight characters and a three-character extension (referred to as 8. ...


NTFS, introduced with the Windows NT operating system, allowed ACL-based permission control. Hard links, multiple file streams, attribute indexing, quota tracking, compression and mount-points for other file systems (called "junctions") are also supported, though not all these features are well-documented. Windows NT (New Technology) is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. ... In computer security, an access control list (ACL) is a list of permissions attached to an object. ...


Unlike many other operating systems, Windows uses a drive letter abstraction at the user level to distinguish one disk or partition from another. For example, the path C:WINDOWS represents a directory WINDOWS on the partition represented by the letter C. The C drive is most commonly used for the primary hard disk partition, on which Windows is installed and from which it boots. This "tradition" has become so firmly ingrained that bugs came about in older versions of Windows which made assumptions that the drive that the operating system was installed on was C. The tradition of using "C" for the drive letter can be traced to MS-DOS, where the letters A and B were reserved for up to two floppy disk drives; in a common configuration, A would be the 3½-inch floppy drive, and B the 5¼-inch one. Network drives may also be mapped to drive letters. A path is the general form of a file or directory name, giving a files name and its unique location in a file system. ... A floppy disk is a data storage device that is composed of a disk of thin, flexible (floppy) magnetic storage medium encased in a square or rectangular plastic shell. ... A floppy disk is a data storage device that is composed of a disk of thin, flexible (floppy) magnetic storage medium encased in a square or rectangular plastic shell. ...


File systems under OpenVMS

Main article: Files-11

Files-11, also known as on-disk structure, is the filesystem used by Hewlett-Packards OpenVMS operating system, and also (in a simpler form) by the older RSX-11. ...

File systems under MVS [IBM Mainframe]

Main article: MVS#MVS filesystem

MVS (Multiple Virtual Storage) was the most commonly used operating system on the System/370 and System/390 IBM mainframe computers. ...

See also

The following lists identify, characterise and link to more thorough information on computer file systems. ... The following tables compare general and technical information for a number of file systems. ... A virtual file system (VFS) or virtual filesystem switch is an abstraction layer on top of a more concrete file system. ... In computing, file system fragmentation, sometimes called file system aging, is the inability of a file system to lay out related data sequentially (contiguously), an inherent phenomenon in storage-backed file systems that allow in-place modification of their contents. ... For other uses, see Distributed file system (disambiguation). ... A filesystem API is an application programming interface that allows developers to add support of a filesystem to an operating system without the operating system needing to know anything about what filesystem it is or how it works. ... Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... This is a list of Unix programs. ... A filename extension is a suffix to the name of a computer file applied to indicate its type. ... In computing, a shared resource is a device or other resource on a computer that is accessed from another computer via a network, as if it were a local resource. ... It has been suggested that this article or section be merged into Filesystem API. (Discuss) A file system driver is a device driver for a file system. ...

References

Cited references

General references

is the 40th day of the year in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 40th day of the year in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 40th day of the year in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 40th day of the year in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 52nd day of the year in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 122nd day of the year (123rd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...

Further reading

External links


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