HOME

TheInfoList



OR:

Network File System (NFS) is a distributed file system protocol originally developed by
Sun Microsystems Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, ...
(Sun) in 1984, allowing a user on a client computer to access files over a
computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections ar ...
much like local storage is accessed. NFS, like many other protocols, builds on the Open Network Computing Remote Procedure Call (ONC RPC) system. NFS is an open IETF standard defined in a
Request for Comments A Request for Comments (RFC) is a publication in a series from the principal technical development and standards-setting bodies for the Internet, most prominently the Internet Engineering Task Force (IETF). An RFC is authored by individuals or ...
(RFC), allowing anyone to implement the protocol.


Versions and variations

Sun used version 1 only for in-house experimental purposes. When the development team added substantial changes to NFS version 1 and released it outside of Sun, they decided to release the new version as v2, so that version interoperation and RPC version fallback could be tested.


NFSv2

Version 2 of the protocol (defined in RFC 1094, March 1989) originally operated only over
User Datagram Protocol In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in packets) to other hosts on an Internet Protocol (IP) networ ...
(UDP). Its designers meant to keep the server side stateless, with locking (for example) implemented outside of the core protocol. People involved in the creation of NFS version 2 include
Russel Sandberg Russel is an alternate spelling of Russell. Russel may also refer to: People *Russel Arnold (born 1973), Sri Lankan cricketer *Russel Crouse (1893–1966), American playwright *Russel Farnham (1784–1832), American frontiersman * Russel Hono ...
,
Bob Lyon Bob Lyon (born March 24, 1955), an American politician, is a former Kansas State Senator from the city of Winchester. A civil engineer, Lyon is a graduate of the University of Virginia and George Washington University.
,
Bill Joy William Nelson Joy (born November 8, 1954) is an American computer engineer and venture capitalist. He co-founded Sun Microsystems in 1982 along with Scott McNealy, Vinod Khosla, and Andy Bechtolsheim, and served as Chief Scientist and CTO a ...
,
Steve Kleiman ''yes'Steve is a masculine given name, usually a short form (hypocorism) of Steven or Stephen Notable people with the name include: steve jops * Steve Abbott (disambiguation), several people * Steve Adams (disambiguation), several people * Steve ...
, and others. The Virtual File System interface allows a modular implementation, reflected in a simple protocol. By February 1986, implementations were demonstrated for operating systems such as System V release 2, DOS, and VAX/VMS using
Eunice Eunice is a feminine given name, from the Greek Εὐνίκη, ''Euníkē'', from "eu", good, and "níkē", victory. Eunice is also a relatively rare last name, found in Nigeria and the Southeastern United States, chiefly Louisiana and Georgia. Pe ...
. NFSv2 only allows the first 2 GB of a file to be read due to
32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32- bit units. Compared to smaller bit widths, 32-bit computers can perform large calcula ...
limitations.


NFSv3

Version 3 (RFC 1813, June 1995) added: * support for 64-bit file sizes and offsets, to handle files larger than 2 gigabytes (GB); * support for asynchronous writes on the server, to improve write performance; * additional file attributes in many replies, to avoid the need to re-fetch them; * a READDIRPLUS operation, to get file handles and attributes along with file names when scanning a directory; * assorted other improvements. The first NFS Version 3 proposal within Sun Microsystems was created not long after the release of NFS Version 2. The principal motivation was an attempt to mitigate the performance issue of the synchronous write operation in NFS Version 2. By July 1992, implementation practice had solved many shortcomings of NFS Version 2, leaving only lack of large file support (64-bit file sizes and offsets) a pressing issue. This became an acute pain point for
Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unti ...
with the introduction of a 64-bit version of Ultrix to support their newly released 64-bit
RISC In computer engineering, a reduced instruction set computer (RISC) is a computer designed to simplify the individual instructions given to the computer to accomplish tasks. Compared to the instructions given to a complex instruction set compu ...
processor, the Alpha 21064. At the time of introduction of Version 3, vendor support for
TCP TCP may refer to: Science and technology * Transformer coupled plasma * Tool Center Point, see Robot end effector Computing * Transmission Control Protocol, a fundamental Internet standard * Telephony control protocol, a Bluetooth communication s ...
as a transport-layer protocol began increasing. While several vendors had already added support for NFS Version 2 with TCP as a transport, Sun Microsystems added support for TCP as a transport for NFS at the same time it added support for Version 3. Using TCP as a transport made using NFS over a WAN more feasible, and allowed the use of larger read and write transfer sizes beyond the 8 KB limit imposed by
User Datagram Protocol In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in packets) to other hosts on an Internet Protocol (IP) networ ...
.


WebNFS

WebNFS was an extension to NFSv2 and NFSv3 allowing it to function behind restrictive firewalls without the complexity of Portmap and MOUNT protocols. WebNFS had a fixed TCP/UDP port number (2049), and instead of requiring the client to contact the MOUNT RPC service to determine the initial filehandle of every filesystem, it introduced the concept of a ''public filehandle'' (null for NFSv2, zero-length for NFSv3) which could be used as the starting point. Both of those changes have later been incorporated into NFSv4.


NFSv4

Version 4 (RFC 3010, December 2000; revised in RFC 3530, April 2003 and again in RFC 7530, March 2015), influenced by Andrew File System (AFS) and Server Message Block (SMB, also termed CIFS), includes performance improvements, mandates strong security, and introduces a
stateful In information technology and computer science, a system is described as stateful if it is designed to remember preceding events or user interactions; the remembered information is called the state of the system. The set of states a system can oc ...
protocol. Version 4 became the first version developed with the
Internet Engineering Task Force The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and ...
(IETF) after
Sun Microsystems Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, ...
handed over the development of the NFS protocols. NFS version 4.1 (RFC 5661, January 2010; revised in RFC 8881, August 2020) aims to provide protocol support to take advantage of clustered server deployments including the ability to provide scalable parallel access to files distributed among multiple servers (pNFS extension). Version 4.1 includes Session trunking mechanism (Also known as NFS Multipathing) and available in some enterprise solutions as VMware ESXi. NFS version 4.2 (RFC 7862) was published in November 2016 with new features including: server-side clone and copy, application I/O advise, sparse files, space reservation, application data block (ADB), labeled NFS with sec_label that accommodates any MAC security system, and two new operations for pNFS (LAYOUTERROR and LAYOUTSTATS). One big advantage of NFSv4 over its predecessors is that only one UDP or TCP port, 2049, is used to run the service, which simplifies using the protocol across firewalls.


Other extensions

WebNFS, an extension to Version 2 and Version 3, allows NFS to integrate more easily into Web-browsers and to enable operation through firewalls. In 2007 Sun Microsystems open-sourced their client-side WebNFS implementation. Various side-band protocols have become associated with NFS. Note: * the byte-range advisory Network Lock Manager (NLM) protocol (added to support
UNIX System V Unix System V (pronounced: "System Five") is one of the first commercial versions of the Unix operating system. It was originally developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, an ...
file locking APIs) * the remote quota-reporting (RQUOTAD) protocol, which allows NFS users to view their data-storage quotas on NFS servers *
NFS over RDMA NFS may refer to: Organisations * NFS (news service) (''Nýja fréttastofan''), a defunct Icelandic television news service * National Film School, former name of the National Film and Television School, England * National Financial Switch, ban ...
, an adaptation of NFS that uses remote direct memory access (RDMA) as a transport * NFS-Ganesha, an NFS server, running in user-space and supporting various file systems like GPFS/Spectrum Scale, CephFS via respective FSAL (File System Abstraction Layer) modules. The
CephFS Ceph (pronounced ) is an open-source software-defined storage platform that implements object storage on a single distributed computer cluster and provides 3-in-1 interfaces for object-, block- and file-level storage. Ceph aims primarily ...
FSAL supported using libcephfs *Trusted NFS (TNFS)


Platforms

NFS is often used with
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 ...
operating systems (such as Solaris, AIX,
HP-UX HP-UX (from "Hewlett Packard Unix") is Hewlett Packard Enterprise's proprietary implementation of the Unix operating system, based on Unix System V (initially System III) and first released in 1984. Current versions support HPE Integrit ...
), Apple's
macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac (computer), Mac computers. Within the market of ...
, 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 systems (such as
Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which i ...
and FreeBSD). It is also available to operating systems such as Acorn RISC OS, AmigaOS, the classic Mac OS,
OpenVMS OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using Ope ...
,
MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few oper ...
, Microsoft Windows,
OS/2 OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 ...
, ArcaOS, Novell NetWare, and IBM i. Alternative remote file access protocols include the Server Message Block (SMB, also termed CIFS),
Apple Filing Protocol The Apple Filing Protocol (AFP), formerly AppleTalk Filing Protocol, is a proprietary network protocol, and part of the Apple File Service (AFS), that offers file services for macOS and the classic Mac OS. In Mac OS 9 and earlier, AFP was t ...
(AFP), NetWare Core Protocol (NCP), and OS/400 File Server file system (QFileSvr.400). SMB and NetWare Core Protocol (NCP) occur more often than NFS on systems running Microsoft Windows; AFP occurs more often than NFS in Apple
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 ...
systems; and QFileSvr.400 occurs more often in IBM i systems.
Haiku is a type of short form poetry originally from Japan. Traditional Japanese haiku consist of three phrases that contain a ''kireji'', or "cutting word", 17 ''On (Japanese prosody), on'' (phonetic units similar to syllables) in a 5, 7, 5 pattern, ...
in 2012 added NFSv4 support as part of a Google Summer of Code project.


Typical implementation

Assuming a Unix-style scenario in which one machine (the client) needs access to data stored on another machine (the NFS server): # The server implements NFS daemon processes, running by default as nfsd, to make its data generically available to clients. # The server administrator determines what to make available, exporting the names and parameters of
directories Directory may refer to: * Directory (computing), or folder, a file system structure in which to store computer files * Directory (OpenVMS command) * Directory service, a software application for organizing information about a computer network's ...
, typically using the /etc/exports configuration file and the exportfs command. # The server
security" \n\n\nsecurity.txt is a proposed standard for websites' security information that is meant to allow security researchers to easily report security vulnerabilities. The standard prescribes a text file called \"security.txt\" in the well known locat ...
-administration ensures that it can recognize and approve validated clients. # The server network configuration ensures that appropriate clients can negotiate with it through any firewall system. # The client machine requests access to exported data, typically by issuing a mount command. (The client asks the server (rpcbind) which port the NFS server is using, the client connects to the NFS server (nfsd), nfsd passes the request to mountd) # If all goes well, users on the client machine can then view and interact with mounted
filesystem 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 larg ...
s on the server within the parameters permitted. Note that automation of the NFS mounting process may take place — perhaps using /etc/fstab and/or automounting facilities.


Protocol development

During the development of the ONC protocol (called SunRPC at the time), only Apollo's Network Computing System (NCS) offered comparable functionality. Two competing groups developed over fundamental differences in the two remote procedure call systems. Arguments focused on the method for data-encoding — ONC's External Data Representation (XDR) always rendered integers in big-endian order, even if both peers of the connection had
little-endian In computing, endianness, also known as byte sex, is the order or sequence of bytes of a word of digital data in computer memory. Endianness is primarily expressed as big-endian (BE) or little-endian (LE). A big-endian system stores the most ...
machine-architectures, whereas NCS's method attempted to avoid byte-swap whenever two peers shared a common
endianness In computing, endianness, also known as byte sex, is the order or sequence of bytes of a word of digital data in computer memory. Endianness is primarily expressed as big-endian (BE) or little-endian (LE). A big-endian system stores the most si ...
in their machine-architectures. An industry-group called the Network Computing Forum formed (March 1987) in an (ultimately unsuccessful) attempt to reconcile the two network-computing environments. In 1987, Sun and AT&T announced they would jointly develop AT&T's UNIX System V Release 4. This caused many of AT&T's other licensees of UNIX System to become concerned that this would put Sun in an advantaged position, and ultimately led to Digital Equipment, HP, IBM, and others forming the Open Software Foundation (OSF) in 1988. Ironically, Sun and AT&T had formerly competed over Sun's NFS versus AT&T's Remote File System (RFS), and the quick adoption of NFS over RFS by Digital Equipment, HP, IBM, and many other computer vendors tipped the majority of users in favor of NFS. NFS
interoperability Interoperability is a characteristic of a product or system to work with other products or systems. While the term was initially defined for information technology or systems engineering services to allow for information exchange, a broader def ...
was aided by events called "Connectathons" starting in 1986 that allowed vendor-neutral testing of implementations with each other. OSF adopted the Distributed Computing Environment (DCE) and the DCE Distributed File System (DFS) over Sun/ONC RPC and NFS. DFS used DCE as the RPC, and DFS derived from the Andrew File System (AFS); DCE itself derived from a suite of technologies, including Apollo's NCS and Kerberos.


1990s

Sun Microsystems and the Internet Society (ISOC) reached an agreement to cede "change control" of ONC RPC so that the ISOC's engineering-standards body, the
Internet Engineering Task Force The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements and ...
(IETF), could publish standards documents (RFCs) related to ONC RPC protocols and could extend ONC RPC. OSF attempted to make DCE RPC an IETF standard, but ultimately proved unwilling to give up change control. Later, the IETF chose to extend ONC RPC by adding a new authentication flavor based on Generic Security Services Application Program Interface (GSSAPI), RPCSEC GSS, to meet IETF requirements that protocol standards have adequate security. Later, Sun and ISOC reached a similar agreement to give ISOC change control over NFS, although writing the contract carefully to exclude NFS version 2 and version 3. Instead, ISOC gained the right to add new versions to the NFS protocol, which resulted in IETF specifying NFS version 4 in 2003.


2000s

By the 21st century, neither DFS nor AFS had achieved any major commercial success as compared to SMB-CIFS or NFS. IBM, which had formerly acquired the primary commercial vendor of DFS and AFS, Transarc, donated most of the AFS source code to the free software community in 2000. The OpenAFS project lives on. In early 2005, IBM announced end of sales for AFS and DFS. In January, 2010,
Panasas Panasas is a data storage company that creates network-attached storage for technical computing environments. History Panasas is a computer data storage product company and is headquartered in San Jose, California. Panasas received seed fundi ...
proposed an NFSv4.1 based on their ''Parallel NFS'' (pNFS) technology claiming to improve data-access parallelism capability. The NFSv4.1 protocol defines a method of separating the filesystem meta-data from file data location; it goes beyond the simple name/data separation by striping the data amongst a set of data servers. This differs from the traditional NFS server which holds the names of files and their data under the single umbrella of the server. Some products are multi-node NFS servers, but the participation of the client in separation of meta-data and data is limited. The NFSv4.1 pNFS server is a set of server resources or components; these are assumed to be controlled by the meta-data server. The pNFS client still accesses one meta-data server for traversal or interaction with the namespace; when the client moves data to and from the server it may directly interact with the set of data servers belonging to the pNFS server collection. The NFSv4.1 client can be enabled to be a direct participant in the exact location of file data and to avoid solitary interaction with one NFS server when moving data. In addition to pNFS, NFSv4.1 provides: * Sessions * Directory Delegation and Notifications * Multi-server Namespace * access control lists and discretionary access control * Retention Attributions * SECINFO_NO_NAME


See also

*
9P (protocol) 9P (or the Plan 9 Filesystem Protocol or Styx) is a network protocol developed for the Plan 9 from Bell Labs distributed operating system as the means of connecting the components of a Plan 9 system. Files are key objects in Plan 9. They repr ...
– Plan 9 Filesystem Protocol *
Alluxio Alluxio is an open-source virtual distributed file system (VDFS). Initially as research project "Tachyon", Alluxio was created at the University of California, Berkeley's AMPLab as Haoyuan Li's Ph.D. Thesis, advised by Professor Scott Shenker ...
* Andrew File System * BeeGFS, the parallel file system *
CacheFS CacheFS is the name used for several similar software technologies designed to speed up distributed file system file access for networked computers. These technologies operate by storing ( cached) copies of files on secondary memory, typically a loc ...
– a caching mechanism for Linux NFS clients * Hadoop Distributed File System ( HDFS) * Kerberos (protocol) * Network Information Service * Remote File System *
Root squash Unix security refers to the means of securing a Unix or Unix-like operating system. A secure environment is achieved not only by the design concepts of these operating systems, but also through vigilant user and administrative practices. Design c ...
* Samba (software) *
Secure Shell Filesystem In computing, SSHFS (SSH Filesystem) is a filesystem client to mount and interact with directories and files located on a remote server or workstation over a normal ssh connection. The client interacts with the remote file system via the SSH ...
– mount a remote directory using only a ssh login on the remote computer * Server Message Block * Shared resource * TCP Wrapper


References


External links

* RFCs: ** – Network File System (NFS) Version 4 Minor Version 1 Protocol ** – RPCSEC_GSS Version 2 ** – NFS Version 4 Protocol Specification ** – WebNFS Specification ** – Sun/ISOC NFS Change Control Agreement ** – RPCSEC_GSS Specification ** – NFS Version 3 Protocol Specification ** – Sun/ISOC ONC RPC Change Control Agreement ** – NFS Version 2 Protocol Specification * Various resources: *
IETF: Network File System Version 4 (nfsv4) Charter
*
Linux NFS Overview, FAQ and HOWTO Documents
*
NFS operation explained with sequence diagrams


by Mike Eisler, October 27, 2006 {{DEFAULTSORT:Network File System (Protocol) Internet protocols Network file systems Internet Protocol based network software Unix network-related software Application layer protocols Network file transfer protocols Distributed file systems Network booting