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Linux Nfs For Mac Windows 7 NTFS-3G Developer(s) Tuxera Inc. Stable release Written in C Operating system Unix-like, Haiku Type License Dual-licensed GNU GPL/Proprietary [ citation needed ] Website www.tuxera.com/community/open-source-ntfs-3g/
NTFS-3G is an open-sourcecross-platform implementation of the Microsoft WindowsNTFS file system with read/write support. NTFS-3G often uses the FUSEfile system interface, so it can run unmodified on many different operating systems. It is runnable on Linux, FreeBSD, NetBSD, OpenSolaris, illumos, BeOS, QNX, WinCE, Nucleus, VxWorks, Haiku, [1] MorphOS, Minix, macOS [2] and OpenBSD. [3] [4] It is licensed under the GNU General Public License. It is a partial fork of ntfsprogs and is under active maintenance and development.
After trying several unsucessful attempts to connect to a Linux NFS, I've found the cause of not being able to connect. Here's how to connect successfully: Set up the Linux NFS per these instructions. In the /etc/exports file, be sure to add the parameter of insecure to the IP of the Mac client machine. This is the cause of not connecting properly. Microsoft NTFS for Mac by Paragon Software is the best such software solution: reliable, fast, and now affordable as well Fast, seamless, and easy to use, Microsoft NTFS for Mac by Paragon Software is required for those who need to write to Windows volumes. And now its more affordable than ever. MacWorld, USA 2016, macworld.com. What you need in linux is ntfs-3g from tuxera.com. It is open-source, and included with many linux distributions, however. Being a SLES 11.4, and RHEL 6.9 to 7.6 user, my experience with windows 10 is that something has changed in how the NTFS system is done (compared to win7) where older versions of ntfs-3g which come with your linux distro.
NTFS-3G was introduced by one of the senior Linux NTFS developers, Szabolcs Szakacsits, in July 2006. The first stable version was released on February 21, 2007, as version 1.0. The developers of NTFS-3G later formed a company, Tuxera Inc., to further develop the code. NTFS-3G is now the free 'community edition', [1] [ failed verification ] while Tuxera NTFS is the proprietary version. Features [ edit ]
NTFS-3G supports all operations for writing files: files of any size can be created, modified, renamed, moved, or deleted on NTFS partitions. Transparent compression is supported, as well as system-level encryption. [5] Support to modify access control lists and permissions is available. [6] NTFS partitions are mounted using the Filesystem in Userspace (FUSE) interface. NTFS-3G supports hard links, symbolic links, and junctions. With the help of NTFS reparse point plugins, it can be made to read chunk-deduplicated files, system-compressed files, and OneDrive files. [7] NTFS-3G provides complete support and translation of NTFS access control list (ACL) to POSIX ACL permissions. A 'usermap' utility is included to record the mapping from UIDs to Windows NT SIDs.
NTFS-3G supports partial NTFS journaling, so if an unexpected computer failure leaves the file system in an inconsistent state, the volume can be repaired. As of 2009, a volume having an unclean journal file is recovered and mounted by default. The norecover mount option can be used to disable this behavior. [8] Performance [ edit ]
Benchmarks show that the driver's performance via FUSE is comparable to that of other filesystems' drivers in-kernel, [9] provided that the CPU is powerful enough. On embedded or old systems, the high processor usage can severely limit performance. Tuxera sells optimized versions of the driver that claims to have improved CPU utilization for embedded systems and MacOS. [10]
The slowness of NTFS-3G (and FUSE in general) on embedded systems is attributed to the frequent context switching associated with FUSE calls. Some open-source methods provided to reduce this overhead include: [11]
The underlying FUSE layer has an option called big_writes to use larger blocks when writing. Using a larger block means fewer context switches. This is in fact a solution recommended by Tuxera. [12] A patch is available to use an even larger block. [13]
There is also a Linux kernel option called lazytime to reduce the writes on file access.
Synology Inc. uses a modified NTFS-3G on their NAS systems. It replaces the ntfs-3g inode caching CACHE_NIDATA_SIZE with a different mechanism with unsure benefit. (It also includes an alternative Security Identifier translation for the NAS.) History [ edit ]
NTFS-3G forked from the Linux-NTFS project on October 31, 2006.
On February 21, 2007, Szabolcs Szakacsits announced 'the release of the first open-source, freely available, stable read/write NTFS driver, NTFS-3G 1.0.'
On October 5, 2009, NTFS-3G for Mac was brought under the auspices of Tuxera Ltd. and a proprietary version called Tuxera NTFS for Mac was made available. [14]
On April 12, 2011, it was announced that Ntfsprogs project was merged with NTFS-3G. [15]
NTFS-3g added TRIM support in version 2015.3.14. See also [ edit ] References [ edit ]
a b c 'STABLE Version 2017.3.23 (March 28, 2017)'. Tuxera . Tuxera. 2017-03-23 . Retrieved 2017-03-23 .
NTFS-3G for Mac OS X ('Catacombae')
'OpenBSD adds fuse(4) support for adding file systems in userland'. OpenBSD Journal. 2013-11-08 . Retrieved 2013-11-08 .
'ntfs_3g-2014.2.15 FUSE NTFS driver with read/write support'. OpenBSD ports . 2014-01-05 . Retrieved 2015-02-14 .
NTFS-3G FAQ
NTFS-3G: NTFS Driver with Ownership and permissions
Andr, Jean-Pierre (March 1, 2019). 'NTFS-3G: Junction Points, Symbolic Links and Reparse Points'. jp-andre.pagesperso-orange.fr .
'NTFS-3G 2009.2.1 changelog'. Archived from the original on 2009-03-23 . Retrieved 2012-09-10 .
Comparing NTFS-3G to ZFS-FUSE for FUSE Performance
Performance at Tuxera
Gothe, Markus. 'On Linux NTFS Performance' . Retrieved 3 October 2019 .
'NTFS-3G Questions'. Tuxera . Workaround: using the mount option big_writes generally reduces the CPU usage, provided the software requesting the writes supports big blocks.
Wang, M. 'linux - Disadvantages of ntfs-3g big_writes mount option'. Unix Linux Stack Exchange . Retrieved 3 October 2019 .
NTFS-3G for Mac OS X is now Tuxera NTFS for Mac
Release: NTFS-3G + NTFSPROGS 2011.4.12 External links [ edit ] Retrieved from 'https://en.wikipedia.org/w/index.php?title=NTFS-3Goldid=958820922' Name
nfs - fstab format and options for the nfs file systems Synopsis
/etc/fstab Description
NFS is an Internet Standard protocol created by Sun Microsystems in 1984. NFS was developed to allow file sharing between systems residing on a local areanetwork. The Linux NFS client supports three versions of the NFS protocol: NFS version 2 [RFC1094], NFS version 3 [RFC1813], and NFS version 4 [RFC3530].
The mount (8) command attaches a file system to the system's name space hierarchy at a given mount point. The /etc/fstab file describes how mount (8) should assemble a system's file name hierarchy from various independent file systems (including file systems exported by NFS servers). Eachline in the /etc/fstab file describes a single file system, its mount point, and a set of default mount options for that mount point.
For NFS file system mounts, a line in the /etc/fstab file specifies the server name, the path name of the exported server directory to mount, thelocal directory that is the mount point, the type of file system that is being mounted, and a list of mount options that control the way the filesystem ismounted and how the NFS client behaves when accessing files on this mount point. The fifth and sixth fields on each line are not used by NFS, thusconventionally each contain the digit zero. For example: server:path
/mountpoint
fstype
option,option,..
0 0 The server's hostname and export pathname are separated by a colon, while the mount options are separated by commas. The remaining fields are separated byblanks or tabs.
The server's hostname can be an unqualified hostname, a fully qualified domain name, a dotted quad IPv4 address, or an IPv6 address enclosed in squarebrackets. Link-local and site-local IPv6 addresses must be accompanied by an interface identifier. See ipv6 (7) for details on specifying raw IPv6addresses.
The fstype field contains 'nfs'. Use of the 'nfs4' fstype in /etc/fstab is deprecated. Mount Options
Refer to mount (8) for a description of generic mount options available for all file systems. If you do not need to specify any mount options, use thegeneric option defaults in /etc/fstab .
Options supported by all versions These options are valid to use with any NFS version. soft / hard
Determines the recovery behavior of the NFS client after an NFS request times out. If neither option is specified (or if the hard option isspecified), NFS requests are retried indefinitely. If the soft option is specified, then the NFS client fails an NFS request after retrans retransmissions have been sent, causing the NFS client to return an error to the calling application.
NB: A so-called 'soft' timeout can cause silent data corruption in certain cases. As such, use the soft option only when client responsivenessis more important than data integrity. Using NFS over TCP or increasing the value of the retrans option may mitigate some of the risks of using the soft option. timeo= n
The time in deciseconds (tenths of a second) the NFS client waits for a response before it retries an NFS request.
For NFS over TCP the default timeo value is 600 (60 seconds). The NFS client performs linear backoff: After each retransmission the timeout isincreased by timeo up to the maximum of 600 seconds.
However, for NFS over UDP, the client uses an adaptive algorithm to estimate an appropriate timeout value for frequently used request types (such as READand WRITE requests), but uses the timeo setting for infrequently used request types (such as FSINFO requests). If the timeo option is notspecified, infrequently used request types are retried after 1.1 seconds. After each retransmission, the NFS client doubles the timeout for that request, up toa maximum timeout length of 60 seconds. retrans= n
The number of times the NFS client retries a request before it attempts further recovery action. If the retrans option is not specified, the NFSclient tries each request three times.
The NFS client generates a 'server not responding' message after retrans retries, then attempts further recovery (depending on whether the hard mount option is in effect). rsize= n
The maximum number of bytes in each network READ request that the NFS client can receive when reading data from a file on an NFS server. The actual datapayload size of each NFS READ request is equal to or smaller than the rsize See full list on screenshot.net . setting. The largest read payload supported by the Linux NFS client is1,048,576 bytes (one megabyte).
The rsize value is a positive integral multiple of 1024. Specified rsize values lower than 1024 are replaced with 4096; values larger than1048576 are replaced with 1048576. If a specified value is within the supported range but not a multiple of 1024, it is rounded down to the nearest multiple of1024.
If an rsize value is not specified, or if the specified rsize value is larger than the maximum that either client or server can support, theclient and server negotiate the largest rsize value that they can both support.
The rsize mount option as specified on the mount (8) command line appears in the /etc/mtab file. However, the effective rsize value negotiated by the client and server is reported in the /proc/mounts file. wsize= n
The maximum number of bytes per network WRITE request that the NFS client can send when writing data to a file on an NFS server. The actual data payloadsize of each NFS WRITE request is equal to or smaller than the wsize setting. The largest write payload supported by the Linux NFS client is 1,048,576bytes (one megabyte).
Similar to rsize , the wsize value is a positive integral multiple of 1024. Specified wsize values lower than 1024 are replaced with4096; values larger than 1048576 are replaced with 1048576. If a specified value is within the supported range but not a multiple of 1024, it is rounded downto the nearest multiple of 1024.
If a wsize value is not specified, or if the specified wsize value is larger than the maximum that either client or server can support, theclient and server negotiate the largest wsize value that they can both support.
The wsize mount option as specified on the mount (8) command line appears in the /etc/mtab file. However, the effective wsize value negotiated by the client and server is reported in the /proc/mounts file. ac / noac
Selects whether the client may cache file attributes. If neither option is specified (or if ac is specified), the client caches fileattributes.
To improve performance, NFS clients cache file attributes. Every few seconds, an NFS client checks the server's version of each file's attributes forupdates. Changes that occur on the server in those small intervals remain undetected until the client checks the server again. The noac option preventsclients from caching file attributes so that applications can more quickly detect file changes on the server.
In addition to preventing the client from caching file attributes, the noac option forces application writes to become synchronous so that localchanges to a file become visible on the server immediately. That way, other clients can quickly detect recent writes when they check the file's attributes.
Using the noac option provides greater cache coherence among NFS clients accessing the same files, but it extracts a significant performance penalty.As such, judicious use of file locking is encouraged instead. The DATA AND METADATA COHERENCE section contains a detailed discussion of thesetrade-offs. acregmin= n
The minimum time (in seconds) that the NFS client caches attributes of a regular file before it requests fresh attribute information from a server. If thisoption is not specified, the NFS client uses a 3-second minimum.
acregmax= n
The maximum time (in seconds) that the NFS client caches attributes of a regular file before it requests fresh attribute information from a server. If thisoption is not specified, the NFS client uses a 60-second maximum.
acdirmin= n
The minimum time (in seconds) that the NFS client caches attributes of a directory before it requests fresh attribute information from a server. If thisoption is not specified, the NFS client uses a 30-second minimum.
acdirmax= n
The maximum time (in seconds) that the NFS client caches attributes of a directory before it requests fresh attribute information from a server. If thisoption is not specified, the NFS client uses a 60-second maximum.
actimeo= n
Using actimeo sets all of acregmin , acregmax , acdirmin , and acdirmax to the same value. If this option is not specified,the NFS client uses the defaults for each of these options listed above.
bg / fg
Determines how the mount (8) command behaves if an attempt to mount an export fails. The fg option causes mount (8) to exit with an errorstatus if any part of the mount request times out or fails outright. This is called a 'foreground' mount, and is the default behavior if neither the fg nor bg mount option is specified.
If the bg option is specified, a timeout or failure causes the mount (8) command to fork a child which continues to attempt to mount theexport. The parent immediately returns with a zero exit code. This is known as a 'background' mount.
If the local mount point directory is missing, the mount (8) command acts as if the mount request timed out. This permits nested NFS mounts specifiedin /etc/fstab to proceed in any order during system initialization, even if some NFS servers are not yet available. Alternatively these issues can beaddressed using an automounter (refer to automount (8) for details). retry= n
The number of minutes that the mount (8) command retries an NFS mount operation in the foreground or background before giving up. If this option isnot specified, the default value for foreground mounts is 2 minutes, and the default value for background mounts is 10000 minutes (80 minutes shy of one week).If a value of zero is specified, the mount (8) command exits immediately after the first failure.
sec= mode
The RPCGSS security flavor to use for accessing files on this mount point. If the sec option is not specified, or if sec=sys is specified, theNFS client uses the AUTH_SYS security flavor for all NFS requests on this mount point. Valid security flavors are none , sys , krb5 , krb5i , krb5p , lkey , lkeyi , lkeyp , spkm , spkmi , and spkmp . Refer to the SECURITY CONSIDERATIONS sectionfor details. sharecache / nosharecache
Determines how the client's data cache and attribute cache are shared when mounting the same export more than once concurrently. Using the same cachereduces memory requirements on the client and presents identical file contents to applications when the same remote file is accessed via different mountpoints.
If neither option is specified, or if the sharecache option is specified, then a single cache is used for all mount points that access the sameexport. If the nosharecache option is specified, then that mount point gets a unique cache. Note that when data and attribute caches are shared, themount options from the first mount point take effect for subsequent concurrent mounts of the same export.
As of kernel 2.6.18, the behavior specified by nosharecache is legacy caching behavior. This is considered a data risk since multiple cached copiesof the same file on the same client can become out of sync following a local update of one of the copies. resvport / noresvport
Specifies whether the NFS client should use a privileged source port when communicating with an NFS server for this mount point. If this option is notspecified, or the resvport option is specified, the NFS client uses a privileged source port. If the noresvport option is specified, the NFSclient uses a non-privileged source port. This option is supported in kernels 2.6.28 and later.
Using non-privileged source ports helps increase the maximum number of NFS mount points allowed on a client, but NFS servers must be configured to allowclients to connect via non-privileged source ports.
Refer to the SECURITY CONSIDERATIONS section for important details. lookupcache= mode
Specifies how the kernel manages its cache of directory entries for a given mount point. mode can be one of all , none , pos , or positive . This option is supported in kernels 2.6.28 and later.
The Linux NFS client caches the result of all NFS LOOKUP requests. If the requested directory entry exists on the server, the result is referred to as positive . If the requested directory entry does not exist on the server, the result is referred to as negative .
If this option is not specified, or if all Is 256 ssd enough for macbook pro . is specified, the client assumes both types of directory cache entries are valid until their parentdirectory's cached attributes expire.
If pos or positive is specified, the client assumes positive entries are valid until their parent directory's cached attributes expire, butalways revalidates negative entires before an application can use them.
If none is specified, the client revalidates both types of directory cache entries before an application can use them. This permits quick detectionof files that were created or removed by other clients, but can impact application and server performance.
The DATA AND METADATA COHERENCE section contains a detailed discussion of these trade-offs.
Options for NFS versions 2 and 3 only Use these options, along with the options in the above subsection, for NFS versions 2 and 3 only. proto= netid
The transport protocol name and protocol family the NFS client uses to transmit requests to the NFS server for this mount point. If an NFS server has bothan IPv4 and an IPv6 address, using a specific netid will force the use of IPv4 or IPv6 networking to communicate with that server.
If support for TI-RPC is built into the mount.nfs command, netid is a valid netid listed in /etc/netconfig . The value 'rdma' may alsobe specified. If the mount.nfs command does not have TI-RPC support, then netid is one of 'tcp,' 'udp,' or 'rdma,' and only IPv4 may be used.
Each transport protocol uses different default retrans and timeo settings. Refer to the description of these two mount options for details.
In addition to controlling how the NFS client transmits requests to the server, this mount option also controls how the mount (8) command communicateswith the server's rpcbind and mountd services. Specifying a netid that uses TCP forces all traffic from the mount (8) command and the NFS client to useTCP. Specifying a netid that uses UDP forces all traffic types to use UDP.
If the proto mount option is not specified, the mount (8) command discovers which protocols the server supports and chooses an appropriatetransport for each service. Refer to the TRANSPORT METHODS section for more details. udp
The udp option is an alternative to specifying proto=udp. It is included for compatibility with other operating systems.
tcp
The tcp option is an alternative to specifying proto=tcp. It is included for compatibility with other operating systems.
rdma
The rdma option is an alternative to specifying proto=rdma.
port= n
The numeric value of the server's NFS service port. If the server's NFS service is not available on the specified port, the mount request fails.
If this option is not specified, or if the specified port value is 0, then the NFS client uses the NFS service port number advertised by the server'srpcbind service. The mount request fails if the server's rpcbind service is not available, the server's NFS service is not registered with its rpcbind service,or the server's NFS service is not available on the advertised port. mountport= n
The numeric value of the server's mountd port. If the server's mountd service is not available on the specified port, the mount request fails. Ntfs Mac Os
If this option is not specified, or if the specified port value is 0, then the mount (8) command uses the mountd service port number advertised by theserver's rpcbind service. The mount request fails if the server's rpcbind service is not available, the server's mountd service is not registered with itsrpcbind service, or the server's mountd service is not available on the advertised port.
This option can be used when mounting an NFS server through a firewall that blocks the rpcbind protocol. mountproto= netid
The transport protocol name and protocol family the NFS client uses to transmit requests to the NFS server' s= mountd= service= when= performing= this= mountrequest,= and= when= later= unmounting= this= mount=
If support for TI-RPC is built into the mount.nfs command, netid is a valid netid listed in /etc/netconfig . Otherwise, netid isone of 'tcp' or 'udp,' and only IPv4 may be used. Ntfs For Mac
This option can be used when mounting an NFS server through a firewall that blocks a particular transport. When used in combination with the proto option, different transports for mountd requests and NFS requests can be specified. If the server's mountd service is not available via the specifiedtransport, the mount request fails.
Refer to the TRANSPORT METHODS section for more on how the mountproto mount option interacts with the proto mount option. mounthost= name
The hostname of the host running mountd. If this option is not specified, the mount (8) command assumes that the mountd service runs on the same hostas the NFS service.
mountvers= n
The RPC version number used to contact the server's mountd. If this option is not specified, the client uses a version number appropriate to the requestedNFS version. This option is useful when multiple NFS services are running on the same remote server host.
namlen= n
The maximum length of a pathname component on this mount. If this option is not specified, the maximum length is negotiated with the server. In most cases,this maximum length is 255 characters.
Some early versions of NFS did not support this negotiation. Using this option ensures that pathconf (3) reports the proper maximum component lengthto applications in such cases. nfsvers= n
The NFS protocol version number used to contact the server's NFS service. If the server does not support the requested version, the mount request fails. Ifthis option is not specified, the client negotiates a suitable version with the server, trying version 4 first, version 3 second, and version 2 last.
vers= n
This option is an alternative to the nfsvers option. It is included for compatibility with other operating systems.
lock / nolock
Selects whether to use the NLM sideband protocol to lock files on the server. If neither option is specified (or if lock is specified), NLM lockingis used for this mount point. When using the nolock option, applications can lock files, but such locks provide exclusion only against otherapplications running on the same client. Remote applications are not affected by these locks.
NLM locking must be disabled with the nolock option when using NFS to mount /var because /var contains files used by the NLMimplementation on Linux. Using the nolock option is also required when mounting exports on NFS servers that do not support the NLM protocol. intr / nointr
Selects whether to allow signals to interrupt file operations on this mount point. If neither option is specified (or if nointr is specified),signals do not interrupt NFS file operations. If intr is specified, system calls return EINTR if an in-progress NFS operation is interrupted by asignal.
Using the intr option is preferred to using the soft option because it is significantly less likely to result in data corruption.
The intr / nointr mount option is deprecated after kernel 2.6.25. Only SIGKILL can interrupt a pending NFS operation on these kernels, and ifspecified, this mount option is ignored to provide backwards compatibility with older kernels. cto / nocto
Selects whether to use close-to-open cache coherence semantics. If neither option is specified (or if cto is specified), the client usesclose-to-open cache coherence semantics. If the nocto option is specified, the client uses a non-standard heuristic to determine when files on theserver have changed.
Using the nocto option may improve performance for read-only mounts, but should be used only if the data on the server changes only occasionally. TheDATA AND METADATA COHERENCE section discusses the behavior of this option in more detail. acl / noacl
Selects whether to use the NFSACL sideband protocol on this mount point. The NFSACL sideband protocol is a proprietary protocol implemented in Solaris thatmanages Access Control Lists. NFSACL was never made a standard part of the NFS protocol specification.
If neither acl nor noacl option is specified, the NFS client negotiates with the server to see if the NFSACL protocol is supported, and usesit if the server supports it. Disabling the NFSACL sideband protocol may be necessary if the negotiation causes problems on the client or server. Refer to theSECURITY CONSIDERATIONS section for more details. rdirplus / nordirplus
Selects whether to use NFS version 3 READDIRPLUS requests. If this option is not specified, the NFS client uses READDIRPLUS requests on NFS version 3 mountsto read small directories. Some applications perform better if the client uses only READDIR requests for all directories. local_lock= mechanism
Specifies whether to use local locking for any or both of the flock and the POSIX locking mechanisms. mechanism can be one of all , flock , posix , or none . This option is supported in kernels 2.6.37 and later.
The Linux NFS client provides a way to make locks local. This means, the applications can lock files, but such locks provide exclusion only against otherapplications running on the same client. Remote applications are not affected by these locks.
If this option is not specified, or if none is specified, the client assumes that the locks are not local.
If all is specified, the client assumes that both flock and POSIX locks are local.
If flock is specified, the client assumes that only flock locks are local and uses NLM sideband protocol to lock files when POSIX locks are used.
If posix is specified, the client assumes that POSIX locks are local and uses NLM sideband protocol to lock files when flock locks are used.
To support legacy flock behavior similar to that of NFS clients 2.6.12, use Samba as Samba maps Windows share mode locks as flock. Since NFS clients 2.6.12 implement flock by emulating POSIX locks, this will result in conflicting locks.
NOTE: When used together, the 'local_lock' mount option will be overridden by 'nolock'/'lock' mount option.
Options for NFS version 4 only Use these options, along with the options in the first subsection above, for NFS version 4 and newer. minorversion= n
Specifies the protocol minor version number. NFSv4 introduces 'minor versioning,' where NFS protocol enhancements can be introduced without bumping the NFSprotocol version number.
The minor version can also be be specified using the vers= option. For example, specifying vers=4.1 is the same as specifying vers=4,minorversion=1 . proto= netid
The transport protocol name and protocol family the NFS client uses to transmit requests to the NFS server for this mount point. If an NFS server has bothan IPv4 and an IPv6 address, using a specific netid will force the use of IPv4 or IPv6 networking to communicate with that server.
If support for TI-RPC is built into the mount.nfs command, netid is a valid netid listed in /etc/netconfig . Otherwise, netid isone of 'tcp' or 'udp,' and only IPv4 may be used.
All NFS version 4 servers are required to support TCP, so if this mount option is not specified, the NFS version 4 client uses the TCP protocol. Refer tothe TRANSPORT METHODS section for more details. port= n
The numeric value of the server's NFS service port. If the server's NFS service is not available on the specified port, the mount request fails.
If this mount option is not specified, the NFS client uses the standard NFS port number of 2049 without first checking the server's rpcbind service. Thisallows an NFS version 4 client to contact an NFS version 4 server through a firewall that may block rpcbind requests.
If the specified port value is 0, then the NFS client uses the NFS service port number advertised by the server's rpcbind service. The mount request failsif the server's rpcbind service is not available, the server's NFS service is not registered with its rpcbind service, or the server's NFS service is notavailable on the advertised port. intr / nointr
Selects whether to allow signals to interrupt file operations on this mount point. If neither option is specified (or if intr is specified), systemcalls return EINTR if an in-progress NFS operation is interrupted by a signal. If nointr is specified, signals do not interrupt NFS operations.
Using the intr option is preferred to using the soft option because it is significantly less likely to result in data corruption.
The intr / nointr mount option is deprecated after kernel 2.6.25. Only SIGKILL can interrupt a pending NFS operation on these kernels, and ifspecified, this mount option is ignored to provide backwards compatibility with older kernels. cto / nocto
Selects whether to use close-to-open cache coherence semantics for NFS directories on this mount point. If neither cto nor nocto is specified,the default is to use close-to-open cache coherence semantics for directories.
File data caching behavior is not affected by this option. The DATA AND METADATA COHERENCE section discusses the behavior of this option in moredetail. clientaddr= n.n.n.n
Specifies a single IPv4 address (in dotted-quad form), or a non-link-local IPv6 address, that the NFS client advertises to allow servers to perform NFSversion 4 callback requests against files on this mount point. If the server is unable to establish callback connections to clients, performance may degrade,or accesses to files may temporarily hang.
If this option is not specified, the mount (8) command attempts to discover an appropriate callback address automatically. The automatic discoveryprocess is not perfect, however. In the presence of multiple client network interfaces, special routing policies, or atypical network topologies, the exactaddress to use for callbacks may be nontrivial to determine. nfs4 FILE SYSTEM TYPE
The nfs4 file system type is an old syntax for specifying NFSv4 usage. It can still be used with all NFSv4-specific and common options, excepted the nfsvers mount option. Mount Configuration File
If the mount command is configured to do so, all of the mount options described in the previous section can also be configured in the /etc/nfsmount.conf file. See nfsmount.conf (5) for details. Examples
To mount an export using NFS version 2, use the nfs file system type and specify the nfsvers=2 mount option. To mount using NFS version 3, usethe nfs file system type and specify the nfsvers=3 mount option. To mount using NFS version 4, use either the nfs file system type, withthe nfsvers=4 mount option, or the nfs4 file system type.
The following example from an /etc/fstab file causes the mount command to negotiate reasonable defaults for NFS behavior. server:/export
/mnt
nfs
defaults
0 0 Here is an example from an /etc/fstab file for an NFS version 2 mount over UDP. server:/export
/mnt
nfs
nfsvers=2,proto=udp
0 0 Try this example to mount using NFS version 4 over TCP with Kerberos 5 mutual authentication. server:/export
/mnt
nfs4
sec=krb5
0 0 This example can be used to mount /usr over NFS. server:/export
/usr
nfs
ro,nolock,nocto,actimeo=3600
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0 0 This example shows how to mount an NFS server using a raw IPv6 link-local address. [fe80::215:c5ff:fb3e:e2b1eth0]:/export
/mnt
nfs
defaults
0 0 Transport Methods
NFS clients send requests to NFS servers via Remote Procedure Calls, or RPCs . The RPC client discovers remote service endpoints automatically,handles per-request authentication, adjusts request parameters for different byte endianness on client and server, and retransmits requests that may have beenlost by the network or server. RPC requests and replies flow over a network transport.
In most cases, the mount (8) command, NFS client, and NFS server can automatically negotiate proper transport and data transfer size settings for amount point. In some cases, however, it pays to specify these settings explicitly using mount options.
Traditionally, NFS clients used the UDP transport exclusively for transmitting requests to servers. Though its implementation is simple, NFS over UDP hasmany limitations that prevent smooth operation and good performance in some common deployment environments. Even an insignificant packet loss rate results inthe loss of whole NFS requests; as such, retransmit timeouts are usually in the subsecond range to allow clients to recover quickly from dropped requests, butthis can result in extraneous network traffic and server load.
However, UDP can be quite effective in specialized settings where the networks MTU is large relative to NFSs data transfer size (such as networkenvironments that enable jumbo Ethernet frames). In such environments, trimming the rsize and wsize settings so that each NFS read or writerequest fits in just a few network frames (or even in a single frame) is advised. This reduces the probability that the loss of a single MTU-sized networkframe results in the loss of an entire large read or write request.
TCP is the default transport protocol used for all modern NFS implementations. It performs well in almost every conceivable network environment and providesexcellent guarantees against data corruption caused by network unreliability. TCP is often a requirement for mounting a server through a network firewall.
Under normal circumstances, networks drop packets much more frequently than NFS servers drop requests. As such, an aggressive retransmit timeout setting forNFS over TCP is unnecessary. Typical timeout settings for NFS over TCP are between one and ten minutes. After the client exhausts its retransmits (the value ofthe retrans mount option), it assumes a network partition has occurred, and attempts to reconnect to the server on a fresh socket. Since TCP itselfmakes network data transfer reliable, rsize and wsize can safely be allowed to default to the largest values supported by both client and server,independent of the network' s= mtu=
Using the mountproto mount option This section applies only to NFS version 2 and version 3 mounts since NFS version 4 does not use a separate protocol for mount requests.
The Linux NFS client can use a different transport for contacting an NFS server's rpcbind service, its mountd service, its Network Lock Manager (NLM)service, and its NFS service. The exact transports employed by the Linux NFS client for each mount point depends on the settings of the transport mountoptions, which include proto , mountproto , udp , and tcp .
The client sends Network Status Manager (NSM) notifications via UDP no matter what transport options are specified, but listens for server NSM notificationson both UDP and TCP. The NFS Access Control List (NFSACL) protocol shares the same transport as the main NFS service.
If no transport options are specified, the Linux NFS client uses UDP to contact the server's mountd service, and TCP to contact its NLM and NFS services bydefault.
If the server does not support these transports for these services, the mount (8) command attempts to discover what the server supports, and thenretries the mount request once using the discovered transports. If the server does not advertise any transport supported by the client or is misconfigured, themount request fails. If the bg option is in effect, the mount command backgrounds itself and continues to attempt the specified mount request.
When the proto option, the udp option, or the tcp option is specified but the mountproto option is not, the specified transportis used to contact both the server's mountd service and for the NLM and NFS services.
If the mountproto option is specified but none of the proto , udp or tcp options are specified, then the specified transport isused for the initial mountd request, but the mount command attempts to discover what the server supports for the NFS protocol, preferring TCP if bothtransports are supported.
If both the mountproto and proto (or udp or tcp ) options are specified, then the transport specified by the mountproto option is used for the initial mountd request, and the transport specified by the proto option (or the udp or tcp options) is used forNFS, no matter what order these options appear. No automatic service discovery is performed if these options are specified.
If any of the proto , udp , tcp , or mountproto options are specified more than once on the same mount command line, then the valueof the rightmost instance of each of these options takes effect. Data And Metadata Coherence
Some modern cluster file systems provide perfect cache coherence among their clients. Perfect cache coherence among disparate NFS clients is expensive toachieve, especially on wide area networks. As such, NFS settles for weaker cache coherence that satisfies the requirements of most file sharing types.Normally, file sharing is completely sequential: first client A opens a file, writes something to it, then closes it; then client B opens the same file, andreads the changes.
Close-to-open cache consistency When an application opens a file stored on an NFS server, the NFS client checks that it still exists on the server and is permitted to the opener by sendinga GETATTR or ACCESS request. When the application closes the file, the NFS client writes back any pending changes to the file so that the next opener can viewthe changes. This also gives the NFS client an opportunity to report any server write errors to the application via the return code from close (2). Thebehavior of checking at open time and flushing at close time is referred to as close-to-open cache consistency.
Weak cache consistency There are still opportunities for a client' s= data= cache= to= contain= stale= data.= the= nfs= version= 3= protocol= introduced= 'weak= cache= consistency'= (also= known= aswcc)= which= provides= a= way= of= efficiently= checking= a= file's= attributes= before= and= after= a= single= request.= this= allows= a= client= to= help= identify= changes= thatcould= have= been= made= by= other=
When a client is using many concurrent operations that update the same file at the same time (for example, during asynchronous write behind), it is stilldifficult to tell whether it was that client's updates or some other client's updates that altered the file.
Attribute caching Use the noac mount option to achieve attribute cache coherence among multiple clients. Almost every file system operation checks file attributeinformation. The client keeps this information cached for a period of time to reduce network and server load. When noac is in effect, a client's fileattribute cache is disabled, so each operation that needs to check a file's attributes is forced to go back to the server. This permits a client to see changesto a file very quickly, at the cost of many extra network operations.
Be careful not to confuse the noac option with 'no data caching.' The noac mount option prevents the client from caching file metadata, butthere are still races that may result in data cache incoherence between client and server.
The NFS protocol is not designed to support true cluster file system cache coherence without some type of application serialization. If absolute cachecoherence among clients is required, applications should use file locking. Alternatively, applications can also open their files with the O_DIRECT flag todisable data caching entirely.
Directory entry caching The Linux NFS client caches the result of all NFS LOOKUP requests. If the requested directory entry exists on the server, the result is referred to as a positive lookup result. If the requested directory entry does not exist on the server (that is, the server returned ENOENT), the result is referred toas negative lookup result.
To detect when directory entries have been added or removed on the server, the Linux NFS client watches a directory's mtime. If the client detects a changein a directory's mtime, the client drops all cached LOOKUP results for that directory. Since the directory's mtime is a cached attribute, it may take some timebefore a client notices it has changed. See the descriptions of the acdirmin , acdirmax , and noac mount options for more information abouthow long a directory's mtime is cached.
Caching directory entries improves the performance of applications that do not share files with applications on other clients. Using cached informationabout directories can interfere with applications that run concurrently on multiple clients and need to detect the creation or removal of files quickly,however. The lookupcache mount option allows some tuning of directory entry caching behavior.
Before kernel release 2.6.28, the Linux NFS client tracked only positive lookup results. This permitted applications to detect new directory entries createdby other clients quickly while still providing some of the performance benefits of caching. If an application depends on the previous lookup caching behaviorof the Linux NFS client, you can use lookupcache=positive .
If the client ignores its cache and validates every application lookup request with the server, that client can immediately detect when a new directoryentry has been either created or removed by another client. You can specify this behavior using lookupcache=none . The extra NFS requests needed if theclient does not cache directory entries can exact a performance penalty. Disabling lookup caching should result in less of a performance penalty than using noac , and has no effect on how the NFS client caches the attributes of files. Mac Read Ntfs
The sync mount option The NFS client treats the sync mount option differently than some other file systems (refer to mount (8) for a description of the generic sync and async mount options). If neither sync nor async is specified (or if the async option is specified), the NFS clientdelays sending application writes to the server until any of these events occur: Memory pressure forces reclamation of system memory resources.
An application flushes file data explicitly with sync (2), msync (2), or fsync (3).
An application closes a file with close (2).
The file is locked/unlocked via fcntl (2). In other words, under normal circumstances, data written by an application may not immediately appear on the server that hosts the file.
If the sync option is specified on a mount point, any system call that writes data to files on that mount point causes that data to be flushed to theserver before the system call returns control to user space. This provides greater data cache coherence among clients, but at a significant performance cost.
Applications can use the O_SYNC open flag to force application writes to individual files to go to the server immediately without the use of the sync mount option.
Using file locks with NFS The Network Lock Manager protocol is a separate sideband protocol used to manage file locks in NFS version 2 and version 3. To support lock recovery after aclient or server reboot, a second sideband protocol -- known as the Network Status Manager protocol -- is also required. In NFS version 4, file locking issupported directly in the main NFS protocol, and the NLM and NSM sideband protocols are not used.
In most cases, NLM and NSM services are started automatically, and no extra configuration is required. Configure all NFS clients with fully-qualified domainnames to ensure that NFS servers can find clients to notify them of server reboots.
NLM supports advisory file locks only. To lock NFS files, use fcntl (2) with the F_GETLK and F_SETLK commands. The NFS client converts file locksobtained via flock (2) to advisory locks.
When mounting servers that do not support the NLM protocol, or when mounting an NFS server through a firewall that blocks the NLM service port, specify the nolock mount option. NLM locking must be disabled with the nolock option when using NFS to mount /var because /var contains filesused by the NLM implementation on Linux.
Specifying the nolock option may also be advised to improve the performance of a proprietary application which runs on a single client and uses filelocks extensively.
NFS version 4 caching features The data and metadata caching behavior of NFS version 4 clients is similar to that of earlier versions. However, NFS version 4 adds two features thatimprove cache behavior: change attributes and file delegation .
The change attribute is a new part of NFS file and directory metadata which tracks data changes. It replaces the use of a file's modification andchange time stamps as a way for clients to validate the content of their caches. Change attributes are independent of the time stamp resolution on either theserver or client, however.
A file delegation is a contract between an NFS version 4 client and server that allows the client to treat a file temporarily as if no other clientis accessing it. The server promises to notify the client (via a callback request) if another client attempts to access that file. Once a file has beendelegated to a client, the client can cache that file's data and metadata aggressively without contacting the server.
File delegations come in two flavors: read and write . A read delegation means that the server notifies the client about any otherclients that want to write to the file. A write delegation means that the client gets notified about either read or write accessors.
Servers grant file delegations when a file is opened, and can recall delegations at any time when another client wants access to the file that conflictswith any delegations already granted. Delegations on directories are not supported.
In order to support delegation callback, the server checks the network return path to the client during the client's initial contact with the server. Ifcontact with the client cannot be established, the server simply does not grant any delegations to that client. Security Considerations
NFS servers control access to file data, but they depend on their RPC implementation to provide authentication of NFS requests. Traditional NFS accesscontrol mimics the standard mode bit access control provided in local file systems. Traditional RPC authentication uses a number to represent each user(usually the user's own uid), a number to represent the user's group (the user's gid), and a set of up to 16 auxiliary group numbers to represent other groupsof which the user may be a member.
Typically, file data and user ID values appear unencrypted (i.e. 'in the clear') on the network. Moreover, NFS versions 2 and 3 use separate sidebandprotocols for mounting, locking and unlocking files, and reporting system status of clients and servers. These auxiliary protocols use no authentication.
In addition to combining these sideband protocols with the main NFS protocol, NFS version 4 introduces more advanced forms of access control,authentication, and in-transit data protection. The NFS version 4 specification mandates NFSv4 ACLs, RPCGSS authentication, and RPCGSS security flavors thatprovide per-RPC integrity checking and encryption. Because NFS version 4 combines the function of the sideband protocols into the main NFS protocol, the newsecurity features apply to all NFS version 4 operations including mounting, file locking, and so on. RPCGSS authentication can also be used with NFS versions 2and 3, but does not protect their sideband protocols.
The sec mount option specifies the RPCGSS security mode that is in effect on a given NFS mount point. Specifying sec=krb5 providescryptographic proof of a user's identity in each RPC request. This provides strong verification of the identity of users accessing data on the server. Notethat additional configuration besides adding this mount option is required in order to enable Kerberos security. Refer to the rpc.gssd (8) man page fordetails.
Two additional flavors of Kerberos security are supported: krb5i and krb5p . The krb5i security flavor provides a cryptographicallystrong guarantee that the data in each RPC request has not been tampered with. The krb5p security flavor encrypts every RPC request to prevent dataexposure during network transit; however, expect some performance impact when using integrity checking or encryption. Similar support for other forms ofcryptographic security (such as lipkey and SPKM3) is also available.
The NFS version 4 protocol allows clients and servers to negotiate among multiple security flavors during mount processing. However, Linux does not yetimplement such negotiation. The Linux client specifies a single security flavor at mount time which remains in effect for the lifetime of the mount. If theserver does not support this flavor, the initial mount request is rejected by the server.
Using non-privileged source ports NFS clients usually communicate with NFS servers via network sockets. Each end of a socket is assigned a port value, which is simply a number between 1 and65535 that distinguishes socket endpoints at the same IP address. A socket is uniquely defined by a tuple that includes the transport protocol (TCP or UDP) andthe port values and IP addresses of both endpoints.
The NFS client can choose any source port value for its sockets, but usually chooses a privileged port. A privileged port is a port value less than1024. Only a process with root privileges may create a socket with a privileged source port.
The exact range of privileged source ports that can be chosen is set by a pair of sysctls to avoid choosing a well-known port, such as the port used by ssh.This means the number of source ports available for the NFS client, and therefore the number of socket connections that can be used at the same time, ispractically limited to only a few hundred.
As described above, the traditional default NFS authentication scheme, known as AUTH_SYS, relies on sending local UID and GID numbers to identify usersmaking NFS requests. An NFS server assumes that if a connection comes from a privileged port, the UID and GID numbers in the NFS requests on this connectionhave been verified by the client's kernel or some other local authority. This is an easy system to spoof, but on a trusted physical network between trustedhosts, it is entirely adequate.
Roughly speaking, one socket is used for each NFS mount point. If a client could use non-privileged source ports as well, the number of sockets allowed, andthus the maximum number of concurrent mount points, would be much larger.
Using non-privileged source ports may compromise server security somewhat, since any user on AUTH_SYS mount points can now pretend to be any other whenmaking NFS requests. Thus NFS servers do not support this by default. They explicitly allow it usually via an export option.
To retain good security while allowing as many mount points as possible, it is best to allow non-privileged client connections only if the server and clientboth require strong authentication, such as Kerberos.
Mounting through a firewall A firewall may reside between an NFS client and server, or the client or server may block some of its own ports via IP filter rules. It is still possible tomount an NFS server through a firewall, though some of the mount (8) command's automatic service endpoint discovery mechanisms may not work; thisrequires you to provide specific endpoint details via NFS mount options.
NFS servers normally run a portmapper or rpcbind daemon to advertise their service endpoints to clients. Clients use the rpcbind daemon todetermine: What network port each RPC-based service is using
What transport protocols each RPC-based service supports The rpcbind daemon uses a well-known port number (111) to help clients find a service endpoint. Although NFS often uses a standard port number (2049),auxiliary services such as the NLM service can choose any unused port number at random.
Common firewall configurations block the well-known rpcbind port. In the absense of an rpcbind service, the server administrator fixes the port number ofNFS-related services so that the firewall can allow access to specific NFS service ports. Client administrators then specify the port number for the mountdservice via the mount (8) command's mountport option. It may also be necessary to enforce the use of TCP or UDP if the firewall blocks one ofthose transports.
NFS Access Control Lists Solaris allows NFS version 3 clients direct access to POSIX Access Control Lists stored in its local file systems. This proprietary sideband protocol, knownas NFSACL, provides richer access control than mode bits. Linux implements this protocol for compatibility with the Solaris NFS implementation. The NFSACLprotocol never became a standard part of the NFS version 3 specification, however.
The NFS version 4 specification mandates a new version of Access Control Lists that are semantically richer than POSIX ACLs. NFS version 4 ACLs are notfully compatible with POSIX ACLs; as such, some translation between the two is required in an environment that mixes POSIX ACLs and NFS version4. The Remount Option
Generic mount options such as rw and sync can be modified on NFS mount points using the remount option. See mount (8) for moreinformation on generic mount options.
With few exceptions, NFS-specific options are not able to be modified during a remount. The underlying transport or NFS version cannot be changed by aremount, for example.
Performing a remount on an NFS file system mounted with the noac option may have unintended consequences. The noac option is a combination ofthe generic option sync , and the NFS-specific option actimeo=0 .
Unmounting after a remount For mount points that use NFS versions 2 or 3, the NFS umount subcommand depends on knowing the original set of mount options used to perform the MNToperation. These options are stored on disk by the NFS mount subcommand, and can be erased by a remount.
To ensure that the saved mount options are not erased during a remount, specify either the local mount directory, or the server hostname and exportpathname, but not both, during a remount. For example, mount -o remount,ro /mnt merges the mount option ro with the mount options already saved on disk for the NFS server mounted at /mnt. Files /etc/fstab
file system table Bugs
Before 2.4.7, the Linux NFS client did not support NFS over TCP.
Before 2.4.20, the Linux NFS client used a heuristic to determine whether cached file data was still valid rather than using the standard close-to-opencache coherency method described above.
Starting with 2.4.22, the Linux NFS client employs a Van Jacobsen-based RTT estimator to determine retransmit timeout values when using NFS over UDP.
Before 2.6.0, the Linux NFS client did not support NFS version 4.
Before 2.6.8, the Linux NFS client used only synchronous reads and writes when the rsize and wsize settings were smaller than the system'spage size.
The Linux NFS client does not yet support certain optional features of the NFS version 4 protocol, such as security negotiation, server referrals, and namedattributes. See Also
fstab (5), mount (8), umount (8), mount.nfs (5), umount.nfs (5), exports (5), netconfig (5), ipv6 (7), nfsd (8), sm-notify (8), rpc.statd (8), rpc.idmapd (8), rpc.gssd (8), rpc.svcgssd (8), kerberos (1)
RFC 768 for the UDP specification.
RFC 793 for the TCP specification.
RFC 1094 for the NFS version 2 specification.
RFC 1813 for the NFS version 3 specification.
RFC 1832 for the XDR specification.
RFC 1833 for the RPC bind specification.
RFC 2203 for the RPCSEC GSS API protocol specification.
RFC 3530 for the NFS version 4 specification. Referenced By Ntfs For Mac Download mount.nfs (8), mountd (8), nfsstat Linux Nfs For Mac Windows 7 (8), rpc.rquotad (8), rpcdebug (8), umount.nfs4 (8)
Ntfs For Mac
Mac Read Ntfs
Ntfs For Mac Download
Linux Nfs For Mac Windows 7 NTFS-3G Developer(s) Tuxera Inc. Stable release Written in C Operating system Unix-like, Haiku Type License Dual-licensed GNU GPL/Proprietary [ citation needed ] Website www.tuxera.com/community/open-source-ntfs-3g/
NTFS-3G is an open-sourcecross-platform implementation of the Microsoft WindowsNTFS file system with read/write support. NTFS-3G often uses the FUSEfile system interface, so it can run unmodified on many different operating systems. It is runnable on Linux, FreeBSD, NetBSD, OpenSolaris, illumos, BeOS, QNX, WinCE, Nucleus, VxWorks, Haiku, [1] MorphOS, Minix, macOS [2] and OpenBSD. [3] [4] It is licensed under the GNU General Public License. It is a partial fork of ntfsprogs and is under active maintenance and development.
After trying several unsucessful attempts to connect to a Linux NFS, I've found the cause of not being able to connect. Here's how to connect successfully: Set up the Linux NFS per these instructions. In the /etc/exports file, be sure to add the parameter of insecure to the IP of the Mac client machine. This is the cause of not connecting properly. Microsoft NTFS for Mac by Paragon Software is the best such software solution: reliable, fast, and now affordable as well Fast, seamless, and easy to use, Microsoft NTFS for Mac by Paragon Software is required for those who need to write to Windows volumes. And now its more affordable than ever. MacWorld, USA 2016, macworld.com. What you need in linux is ntfs-3g from tuxera.com. It is open-source, and included with many linux distributions, however. Being a SLES 11.4, and RHEL 6.9 to 7.6 user, my experience with windows 10 is that something has changed in how the NTFS system is done (compared to win7) where older versions of ntfs-3g which come with your linux distro.
NTFS-3G was introduced by one of the senior Linux NTFS developers, Szabolcs Szakacsits, in July 2006. The first stable version was released on February 21, 2007, as version 1.0. The developers of NTFS-3G later formed a company, Tuxera Inc., to further develop the code. NTFS-3G is now the free 'community edition', [1] [ failed verification ] while Tuxera NTFS is the proprietary version. Features [ edit ]
NTFS-3G supports all operations for writing files: files of any size can be created, modified, renamed, moved, or deleted on NTFS partitions. Transparent compression is supported, as well as system-level encryption. [5] Support to modify access control lists and permissions is available. [6] NTFS partitions are mounted using the Filesystem in Userspace (FUSE) interface. NTFS-3G supports hard links, symbolic links, and junctions. With the help of NTFS reparse point plugins, it can be made to read chunk-deduplicated files, system-compressed files, and OneDrive files. [7] NTFS-3G provides complete support and translation of NTFS access control list (ACL) to POSIX ACL permissions. A 'usermap' utility is included to record the mapping from UIDs to Windows NT SIDs.
NTFS-3G supports partial NTFS journaling, so if an unexpected computer failure leaves the file system in an inconsistent state, the volume can be repaired. As of 2009, a volume having an unclean journal file is recovered and mounted by default. The norecover mount option can be used to disable this behavior. [8] Performance [ edit ]
Benchmarks show that the driver's performance via FUSE is comparable to that of other filesystems' drivers in-kernel, [9] provided that the CPU is powerful enough. On embedded or old systems, the high processor usage can severely limit performance. Tuxera sells optimized versions of the driver that claims to have improved CPU utilization for embedded systems and MacOS. [10]
The slowness of NTFS-3G (and FUSE in general) on embedded systems is attributed to the frequent context switching associated with FUSE calls. Some open-source methods provided to reduce this overhead include: [11]
The underlying FUSE layer has an option called big_writes to use larger blocks when writing. Using a larger block means fewer context switches. This is in fact a solution recommended by Tuxera. [12] A patch is available to use an even larger block. [13]
There is also a Linux kernel option called lazytime to reduce the writes on file access.
Synology Inc. uses a modified NTFS-3G on their NAS systems. It replaces the ntfs-3g inode caching CACHE_NIDATA_SIZE with a different mechanism with unsure benefit. (It also includes an alternative Security Identifier translation for the NAS.) History [ edit ]
NTFS-3G forked from the Linux-NTFS project on October 31, 2006.
On February 21, 2007, Szabolcs Szakacsits announced 'the release of the first open-source, freely available, stable read/write NTFS driver, NTFS-3G 1.0.'
On October 5, 2009, NTFS-3G for Mac was brought under the auspices of Tuxera Ltd. and a proprietary version called Tuxera NTFS for Mac was made available. [14]
On April 12, 2011, it was announced that Ntfsprogs project was merged with NTFS-3G. [15]
NTFS-3g added TRIM support in version 2015.3.14. See also [ edit ] References [ edit ]
a b c 'STABLE Version 2017.3.23 (March 28, 2017)'. Tuxera . Tuxera. 2017-03-23 . Retrieved 2017-03-23 .
NTFS-3G for Mac OS X ('Catacombae')
'OpenBSD adds fuse(4) support for adding file systems in userland'. OpenBSD Journal. 2013-11-08 . Retrieved 2013-11-08 .
'ntfs_3g-2014.2.15 FUSE NTFS driver with read/write support'. OpenBSD ports . 2014-01-05 . Retrieved 2015-02-14 .
NTFS-3G FAQ
NTFS-3G: NTFS Driver with Ownership and permissions
Andr, Jean-Pierre (March 1, 2019). 'NTFS-3G: Junction Points, Symbolic Links and Reparse Points'. jp-andre.pagesperso-orange.fr .
'NTFS-3G 2009.2.1 changelog'. Archived from the original on 2009-03-23 . Retrieved 2012-09-10 .
Comparing NTFS-3G to ZFS-FUSE for FUSE Performance
Performance at Tuxera
Gothe, Markus. 'On Linux NTFS Performance' . Retrieved 3 October 2019 .
'NTFS-3G Questions'. Tuxera . Workaround: using the mount option big_writes generally reduces the CPU usage, provided the software requesting the writes supports big blocks.
Wang, M. 'linux - Disadvantages of ntfs-3g big_writes mount option'. Unix Linux Stack Exchange . Retrieved 3 October 2019 .
NTFS-3G for Mac OS X is now Tuxera NTFS for Mac
Release: NTFS-3G + NTFSPROGS 2011.4.12 External links [ edit ] Retrieved from 'https://en.wikipedia.org/w/index.php?title=NTFS-3Goldid=958820922' Name
nfs - fstab format and options for the nfs file systems Synopsis
/etc/fstab Description
NFS is an Internet Standard protocol created by Sun Microsystems in 1984. NFS was developed to allow file sharing between systems residing on a local areanetwork. The Linux NFS client supports three versions of the NFS protocol: NFS version 2 [RFC1094], NFS version 3 [RFC1813], and NFS version 4 [RFC3530].
The mount (8) command attaches a file system to the system's name space hierarchy at a given mount point. The /etc/fstab file describes how mount (8) should assemble a system's file name hierarchy from various independent file systems (including file systems exported by NFS servers). Eachline in the /etc/fstab file describes a single file system, its mount point, and a set of default mount options for that mount point.
For NFS file system mounts, a line in the /etc/fstab file specifies the server name, the path name of the exported server directory to mount, thelocal directory that is the mount point, the type of file system that is being mounted, and a list of mount options that control the way the filesystem ismounted and how the NFS client behaves when accessing files on this mount point. The fifth and sixth fields on each line are not used by NFS, thusconventionally each contain the digit zero. For example: server:path
/mountpoint
fstype
option,option,..
0 0 The server's hostname and export pathname are separated by a colon, while the mount options are separated by commas. The remaining fields are separated byblanks or tabs.
The server's hostname can be an unqualified hostname, a fully qualified domain name, a dotted quad IPv4 address, or an IPv6 address enclosed in squarebrackets. Link-local and site-local IPv6 addresses must be accompanied by an interface identifier. See ipv6 (7) for details on specifying raw IPv6addresses.
The fstype field contains 'nfs'. Use of the 'nfs4' fstype in /etc/fstab is deprecated. Mount Options
Refer to mount (8) for a description of generic mount options available for all file systems. If you do not need to specify any mount options, use thegeneric option defaults in /etc/fstab .
Options supported by all versions These options are valid to use with any NFS version. soft / hard
Determines the recovery behavior of the NFS client after an NFS request times out. If neither option is specified (or if the hard option isspecified), NFS requests are retried indefinitely. If the soft option is specified, then the NFS client fails an NFS request after retrans retransmissions have been sent, causing the NFS client to return an error to the calling application.
NB: A so-called 'soft' timeout can cause silent data corruption in certain cases. As such, use the soft option only when client responsivenessis more important than data integrity. Using NFS over TCP or increasing the value of the retrans option may mitigate some of the risks of using the soft option. timeo= n
The time in deciseconds (tenths of a second) the NFS client waits for a response before it retries an NFS request.
For NFS over TCP the default timeo value is 600 (60 seconds). The NFS client performs linear backoff: After each retransmission the timeout isincreased by timeo up to the maximum of 600 seconds.
However, for NFS over UDP, the client uses an adaptive algorithm to estimate an appropriate timeout value for frequently used request types (such as READand WRITE requests), but uses the timeo setting for infrequently used request types (such as FSINFO requests). If the timeo option is notspecified, infrequently used request types are retried after 1.1 seconds. After each retransmission, the NFS client doubles the timeout for that request, up toa maximum timeout length of 60 seconds. retrans= n
The number of times the NFS client retries a request before it attempts further recovery action. If the retrans option is not specified, the NFSclient tries each request three times.
The NFS client generates a 'server not responding' message after retrans retries, then attempts further recovery (depending on whether the hard mount option is in effect). rsize= n
The maximum number of bytes in each network READ request that the NFS client can receive when reading data from a file on an NFS server. The actual datapayload size of each NFS READ request is equal to or smaller than the rsize See full list on screenshot.net . setting. The largest read payload supported by the Linux NFS client is1,048,576 bytes (one megabyte).
The rsize value is a positive integral multiple of 1024. Specified rsize values lower than 1024 are replaced with 4096; values larger than1048576 are replaced with 1048576. If a specified value is within the supported range but not a multiple of 1024, it is rounded down to the nearest multiple of1024.
If an rsize value is not specified, or if the specified rsize value is larger than the maximum that either client or server can support, theclient and server negotiate the largest rsize value that they can both support.
The rsize mount option as specified on the mount (8) command line appears in the /etc/mtab file. However, the effective rsize value negotiated by the client and server is reported in the /proc/mounts file. wsize= n
The maximum number of bytes per network WRITE request that the NFS client can send when writing data to a file on an NFS server. The actual data payloadsize of each NFS WRITE request is equal to or smaller than the wsize setting. The largest write payload supported by the Linux NFS client is 1,048,576bytes (one megabyte).
Similar to rsize , the wsize value is a positive integral multiple of 1024. Specified wsize values lower than 1024 are replaced with4096; values larger than 1048576 are replaced with 1048576. If a specified value is within the supported range but not a multiple of 1024, it is rounded downto the nearest multiple of 1024.
If a wsize value is not specified, or if the specified wsize value is larger than the maximum that either client or server can support, theclient and server negotiate the largest wsize value that they can both support.
The wsize mount option as specified on the mount (8) command line appears in the /etc/mtab file. However, the effective wsize value negotiated by the client and server is reported in the /proc/mounts file. ac / noac
Selects whether the client may cache file attributes. If neither option is specified (or if ac is specified), the client caches fileattributes.
To improve performance, NFS clients cache file attributes. Every few seconds, an NFS client checks the server's version of each file's attributes forupdates. Changes that occur on the server in those small intervals remain undetected until the client checks the server again. The noac option preventsclients from caching file attributes so that applications can more quickly detect file changes on the server.
In addition to preventing the client from caching file attributes, the noac option forces application writes to become synchronous so that localchanges to a file become visible on the server immediately. That way, other clients can quickly detect recent writes when they check the file's attributes.
Using the noac option provides greater cache coherence among NFS clients accessing the same files, but it extracts a significant performance penalty.As such, judicious use of file locking is encouraged instead. The DATA AND METADATA COHERENCE section contains a detailed discussion of thesetrade-offs. acregmin= n
The minimum time (in seconds) that the NFS client caches attributes of a regular file before it requests fresh attribute information from a server. If thisoption is not specified, the NFS client uses a 3-second minimum.
acregmax= n
The maximum time (in seconds) that the NFS client caches attributes of a regular file before it requests fresh attribute information from a server. If thisoption is not specified, the NFS client uses a 60-second maximum.
acdirmin= n
The minimum time (in seconds) that the NFS client caches attributes of a directory before it requests fresh attribute information from a server. If thisoption is not specified, the NFS client uses a 30-second minimum.
acdirmax= n
The maximum time (in seconds) that the NFS client caches attributes of a directory before it requests fresh attribute information from a server. If thisoption is not specified, the NFS client uses a 60-second maximum.
actimeo= n
Using actimeo sets all of acregmin , acregmax , acdirmin , and acdirmax to the same value. If this option is not specified,the NFS client uses the defaults for each of these options listed above.
bg / fg
Determines how the mount (8) command behaves if an attempt to mount an export fails. The fg option causes mount (8) to exit with an errorstatus if any part of the mount request times out or fails outright. This is called a 'foreground' mount, and is the default behavior if neither the fg nor bg mount option is specified.
If the bg option is specified, a timeout or failure causes the mount (8) command to fork a child which continues to attempt to mount theexport. The parent immediately returns with a zero exit code. This is known as a 'background' mount.
If the local mount point directory is missing, the mount (8) command acts as if the mount request timed out. This permits nested NFS mounts specifiedin /etc/fstab to proceed in any order during system initialization, even if some NFS servers are not yet available. Alternatively these issues can beaddressed using an automounter (refer to automount (8) for details). retry= n
The number of minutes that the mount (8) command retries an NFS mount operation in the foreground or background before giving up. If this option isnot specified, the default value for foreground mounts is 2 minutes, and the default value for background mounts is 10000 minutes (80 minutes shy of one week).If a value of zero is specified, the mount (8) command exits immediately after the first failure.
sec= mode
The RPCGSS security flavor to use for accessing files on this mount point. If the sec option is not specified, or if sec=sys is specified, theNFS client uses the AUTH_SYS security flavor for all NFS requests on this mount point. Valid security flavors are none , sys , krb5 , krb5i , krb5p , lkey , lkeyi , lkeyp , spkm , spkmi , and spkmp . Refer to the SECURITY CONSIDERATIONS sectionfor details. sharecache / nosharecache
Determines how the client's data cache and attribute cache are shared when mounting the same export more than once concurrently. Using the same cachereduces memory requirements on the client and presents identical file contents to applications when the same remote file is accessed via different mountpoints.
If neither option is specified, or if the sharecache option is specified, then a single cache is used for all mount points that access the sameexport. If the nosharecache option is specified, then that mount point gets a unique cache. Note that when data and attribute caches are shared, themount options from the first mount point take effect for subsequent concurrent mounts of the same export.
As of kernel 2.6.18, the behavior specified by nosharecache is legacy caching behavior. This is considered a data risk since multiple cached copiesof the same file on the same client can become out of sync following a local update of one of the copies. resvport / noresvport
Specifies whether the NFS client should use a privileged source port when communicating with an NFS server for this mount point. If this option is notspecified, or the resvport option is specified, the NFS client uses a privileged source port. If the noresvport option is specified, the NFSclient uses a non-privileged source port. This option is supported in kernels 2.6.28 and later.
Using non-privileged source ports helps increase the maximum number of NFS mount points allowed on a client, but NFS servers must be configured to allowclients to connect via non-privileged source ports.
Refer to the SECURITY CONSIDERATIONS section for important details. lookupcache= mode
Specifies how the kernel manages its cache of directory entries for a given mount point. mode can be one of all , none , pos , or positive . This option is supported in kernels 2.6.28 and later.
The Linux NFS client caches the result of all NFS LOOKUP requests. If the requested directory entry exists on the server, the result is referred to as positive . If the requested directory entry does not exist on the server, the result is referred to as negative .
If this option is not specified, or if all Is 256 ssd enough for macbook pro . is specified, the client assumes both types of directory cache entries are valid until their parentdirectory's cached attributes expire.
If pos or positive is specified, the client assumes positive entries are valid until their parent directory's cached attributes expire, butalways revalidates negative entires before an application can use them.
If none is specified, the client revalidates both types of directory cache entries before an application can use them. This permits quick detectionof files that were created or removed by other clients, but can impact application and server performance.
The DATA AND METADATA COHERENCE section contains a detailed discussion of these trade-offs.
Options for NFS versions 2 and 3 only Use these options, along with the options in the above subsection, for NFS versions 2 and 3 only. proto= netid
The transport protocol name and protocol family the NFS client uses to transmit requests to the NFS server for this mount point. If an NFS server has bothan IPv4 and an IPv6 address, using a specific netid will force the use of IPv4 or IPv6 networking to communicate with that server.
If support for TI-RPC is built into the mount.nfs command, netid is a valid netid listed in /etc/netconfig . The value 'rdma' may alsobe specified. If the mount.nfs command does not have TI-RPC support, then netid is one of 'tcp,' 'udp,' or 'rdma,' and only IPv4 may be used.
Each transport protocol uses different default retrans and timeo settings. Refer to the description of these two mount options for details.
In addition to controlling how the NFS client transmits requests to the server, this mount option also controls how the mount (8) command communicateswith the server's rpcbind and mountd services. Specifying a netid that uses TCP forces all traffic from the mount (8) command and the NFS client to useTCP. Specifying a netid that uses UDP forces all traffic types to use UDP.
If the proto mount option is not specified, the mount (8) command discovers which protocols the server supports and chooses an appropriatetransport for each service. Refer to the TRANSPORT METHODS section for more details. udp
The udp option is an alternative to specifying proto=udp. It is included for compatibility with other operating systems.
tcp
The tcp option is an alternative to specifying proto=tcp. It is included for compatibility with other operating systems.
rdma
The rdma option is an alternative to specifying proto=rdma.
port= n
The numeric value of the server's NFS service port. If the server's NFS service is not available on the specified port, the mount request fails.
If this option is not specified, or if the specified port value is 0, then the NFS client uses the NFS service port number advertised by the server'srpcbind service. The mount request fails if the server's rpcbind service is not available, the server's NFS service is not registered with its rpcbind service,or the server's NFS service is not available on the advertised port. mountport= n
The numeric value of the server's mountd port. If the server's mountd service is not available on the specified port, the mount request fails. Ntfs Mac Os
If this option is not specified, or if the specified port value is 0, then the mount (8) command uses the mountd service port number advertised by theserver's rpcbind service. The mount request fails if the server's rpcbind service is not available, the server's mountd service is not registered with itsrpcbind service, or the server's mountd service is not available on the advertised port.
This option can be used when mounting an NFS server through a firewall that blocks the rpcbind protocol. mountproto= netid
The transport protocol name and protocol family the NFS client uses to transmit requests to the NFS server' s= mountd= service= when= performing= this= mountrequest,= and= when= later= unmounting= this= mount=
If support for TI-RPC is built into the mount.nfs command, netid is a valid netid listed in /etc/netconfig . Otherwise, netid isone of 'tcp' or 'udp,' and only IPv4 may be used. Ntfs For Mac
This option can be used when mounting an NFS server through a firewall that blocks a particular transport. When used in combination with the proto option, different transports for mountd requests and NFS requests can be specified. If the server's mountd service is not available via the specifiedtransport, the mount request fails.
Refer to the TRANSPORT METHODS section for more on how the mountproto mount option interacts with the proto mount option. mounthost= name
The hostname of the host running mountd. If this option is not specified, the mount (8) command assumes that the mountd service runs on the same hostas the NFS service.
mountvers= n
The RPC version number used to contact the server's mountd. If this option is not specified, the client uses a version number appropriate to the requestedNFS version. This option is useful when multiple NFS services are running on the same remote server host.
namlen= n
The maximum length of a pathname component on this mount. If this option is not specified, the maximum length is negotiated with the server. In most cases,this maximum length is 255 characters.
Some early versions of NFS did not support this negotiation. Using this option ensures that pathconf (3) reports the proper maximum component lengthto applications in such cases. nfsvers= n
The NFS protocol version number used to contact the server's NFS service. If the server does not support the requested version, the mount request fails. Ifthis option is not specified, the client negotiates a suitable version with the server, trying version 4 first, version 3 second, and version 2 last.
vers= n
This option is an alternative to the nfsvers option. It is included for compatibility with other operating systems.
lock / nolock
Selects whether to use the NLM sideband protocol to lock files on the server. If neither option is specified (or if lock is specified), NLM lockingis used for this mount point. When using the nolock option, applications can lock files, but such locks provide exclusion only against otherapplications running on the same client. Remote applications are not affected by these locks.
NLM locking must be disabled with the nolock option when using NFS to mount /var because /var contains files used by the NLMimplementation on Linux. Using the nolock option is also required when mounting exports on NFS servers that do not support the NLM protocol. intr / nointr
Selects whether to allow signals to interrupt file operations on this mount point. If neither option is specified (or if nointr is specified),signals do not interrupt NFS file operations. If intr is specified, system calls return EINTR if an in-progress NFS operation is interrupted by asignal.
Using the intr option is preferred to using the soft option because it is significantly less likely to result in data corruption.
The intr / nointr mount option is deprecated after kernel 2.6.25. Only SIGKILL can interrupt a pending NFS operation on these kernels, and ifspecified, this mount option is ignored to provide backwards compatibility with older kernels. cto / nocto
Selects whether to use close-to-open cache coherence semantics. If neither option is specified (or if cto is specified), the client usesclose-to-open cache coherence semantics. If the nocto option is specified, the client uses a non-standard heuristic to determine when files on theserver have changed.
Using the nocto option may improve performance for read-only mounts, but should be used only if the data on the server changes only occasionally. TheDATA AND METADATA COHERENCE section discusses the behavior of this option in more detail. acl / noacl
Selects whether to use the NFSACL sideband protocol on this mount point. The NFSACL sideband protocol is a proprietary protocol implemented in Solaris thatmanages Access Control Lists. NFSACL was never made a standard part of the NFS protocol specification.
If neither acl nor noacl option is specified, the NFS client negotiates with the server to see if the NFSACL protocol is supported, and usesit if the server supports it. Disabling the NFSACL sideband protocol may be necessary if the negotiation causes problems on the client or server. Refer to theSECURITY CONSIDERATIONS section for more details. rdirplus / nordirplus
Selects whether to use NFS version 3 READDIRPLUS requests. If this option is not specified, the NFS client uses READDIRPLUS requests on NFS version 3 mountsto read small directories. Some applications perform better if the client uses only READDIR requests for all directories. local_lock= mechanism
Specifies whether to use local locking for any or both of the flock and the POSIX locking mechanisms. mechanism can be one of all , flock , posix , or none . This option is supported in kernels 2.6.37 and later.
The Linux NFS client provides a way to make locks local. This means, the applications can lock files, but such locks provide exclusion only against otherapplications running on the same client. Remote applications are not affected by these locks.
If this option is not specified, or if none is specified, the client assumes that the locks are not local.
If all is specified, the client assumes that both flock and POSIX locks are local.
If flock is specified, the client assumes that only flock locks are local and uses NLM sideband protocol to lock files when POSIX locks are used.
If posix is specified, the client assumes that POSIX locks are local and uses NLM sideband protocol to lock files when flock locks are used.
To support legacy flock behavior similar to that of NFS clients 2.6.12, use Samba as Samba maps Windows share mode locks as flock. Since NFS clients 2.6.12 implement flock by emulating POSIX locks, this will result in conflicting locks.
NOTE: When used together, the 'local_lock' mount option will be overridden by 'nolock'/'lock' mount option.
Options for NFS version 4 only Use these options, along with the options in the first subsection above, for NFS version 4 and newer. minorversion= n
Specifies the protocol minor version number. NFSv4 introduces 'minor versioning,' where NFS protocol enhancements can be introduced without bumping the NFSprotocol version number.
The minor version can also be be specified using the vers= option. For example, specifying vers=4.1 is the same as specifying vers=4,minorversion=1 . proto= netid
The transport protocol name and protocol family the NFS client uses to transmit requests to the NFS server for this mount point. If an NFS server has bothan IPv4 and an IPv6 address, using a specific netid will force the use of IPv4 or IPv6 networking to communicate with that server.
If support for TI-RPC is built into the mount.nfs command, netid is a valid netid listed in /etc/netconfig . Otherwise, netid isone of 'tcp' or 'udp,' and only IPv4 may be used.
All NFS version 4 servers are required to support TCP, so if this mount option is not specified, the NFS version 4 client uses the TCP protocol. Refer tothe TRANSPORT METHODS section for more details. port= n
The numeric value of the server's NFS service port. If the server's NFS service is not available on the specified port, the mount request fails.
If this mount option is not specified, the NFS client uses the standard NFS port number of 2049 without first checking the server's rpcbind service. Thisallows an NFS version 4 client to contact an NFS version 4 server through a firewall that may block rpcbind requests.
If the specified port value is 0, then the NFS client uses the NFS service port number advertised by the server's rpcbind service. The mount request failsif the server's rpcbind service is not available, the server's NFS service is not registered with its rpcbind service, or the server's NFS service is notavailable on the advertised port. intr / nointr
Selects whether to allow signals to interrupt file operations on this mount point. If neither option is specified (or if intr is specified), systemcalls return EINTR if an in-progress NFS operation is interrupted by a signal. If nointr is specified, signals do not interrupt NFS operations.
Using the intr option is preferred to using the soft option because it is significantly less likely to result in data corruption.
The intr / nointr mount option is deprecated after kernel 2.6.25. Only SIGKILL can interrupt a pending NFS operation on these kernels, and ifspecified, this mount option is ignored to provide backwards compatibility with older kernels. cto / nocto
Selects whether to use close-to-open cache coherence semantics for NFS directories on this mount point. If neither cto nor nocto is specified,the default is to use close-to-open cache coherence semantics for directories.
File data caching behavior is not affected by this option. The DATA AND METADATA COHERENCE section discusses the behavior of this option in moredetail. clientaddr= n.n.n.n
Specifies a single IPv4 address (in dotted-quad form), or a non-link-local IPv6 address, that the NFS client advertises to allow servers to perform NFSversion 4 callback requests against files on this mount point. If the server is unable to establish callback connections to clients, performance may degrade,or accesses to files may temporarily hang.
If this option is not specified, the mount (8) command attempts to discover an appropriate callback address automatically. The automatic discoveryprocess is not perfect, however. In the presence of multiple client network interfaces, special routing policies, or atypical network topologies, the exactaddress to use for callbacks may be nontrivial to determine. nfs4 FILE SYSTEM TYPE
The nfs4 file system type is an old syntax for specifying NFSv4 usage. It can still be used with all NFSv4-specific and common options, excepted the nfsvers mount option. Mount Configuration File
If the mount command is configured to do so, all of the mount options described in the previous section can also be configured in the /etc/nfsmount.conf file. See nfsmount.conf (5) for details. Examples
To mount an export using NFS version 2, use the nfs file system type and specify the nfsvers=2 mount option. To mount using NFS version 3, usethe nfs file system type and specify the nfsvers=3 mount option. To mount using NFS version 4, use either the nfs file system type, withthe nfsvers=4 mount option, or the nfs4 file system type.
The following example from an /etc/fstab file causes the mount command to negotiate reasonable defaults for NFS behavior. server:/export
/mnt
nfs
defaults
0 0 Here is an example from an /etc/fstab file for an NFS version 2 mount over UDP. server:/export
/mnt
nfs
nfsvers=2,proto=udp
0 0 Try this example to mount using NFS version 4 over TCP with Kerberos 5 mutual authentication. server:/export
/mnt
nfs4
sec=krb5
0 0 This example can be used to mount /usr over NFS. server:/export
/usr
nfs
ro,nolock,nocto,actimeo=3600
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0 0 This example shows how to mount an NFS server using a raw IPv6 link-local address. [fe80::215:c5ff:fb3e:e2b1eth0]:/export
/mnt
nfs
defaults
0 0 Transport Methods
NFS clients send requests to NFS servers via Remote Procedure Calls, or RPCs . The RPC client discovers remote service endpoints automatically,handles per-request authentication, adjusts request parameters for different byte endianness on client and server, and retransmits requests that may have beenlost by the network or server. RPC requests and replies flow over a network transport.
In most cases, the mount (8) command, NFS client, and NFS server can automatically negotiate proper transport and data transfer size settings for amount point. In some cases, however, it pays to specify these settings explicitly using mount options.
Traditionally, NFS clients used the UDP transport exclusively for transmitting requests to servers. Though its implementation is simple, NFS over UDP hasmany limitations that prevent smooth operation and good performance in some common deployment environments. Even an insignificant packet loss rate results inthe loss of whole NFS requests; as such, retransmit timeouts are usually in the subsecond range to allow clients to recover quickly from dropped requests, butthis can result in extraneous network traffic and server load.
However, UDP can be quite effective in specialized settings where the networks MTU is large relative to NFSs data transfer size (such as networkenvironments that enable jumbo Ethernet frames). In such environments, trimming the rsize and wsize settings so that each NFS read or writerequest fits in just a few network frames (or even in a single frame) is advised. This reduces the probability that the loss of a single MTU-sized networkframe results in the loss of an entire large read or write request.
TCP is the default transport protocol used for all modern NFS implementations. It performs well in almost every conceivable network environment and providesexcellent guarantees against data corruption caused by network unreliability. TCP is often a requirement for mounting a server through a network firewall.
Under normal circumstances, networks drop packets much more frequently than NFS servers drop requests. As such, an aggressive retransmit timeout setting forNFS over TCP is unnecessary. Typical timeout settings for NFS over TCP are between one and ten minutes. After the client exhausts its retransmits (the value ofthe retrans mount option), it assumes a network partition has occurred, and attempts to reconnect to the server on a fresh socket. Since TCP itselfmakes network data transfer reliable, rsize and wsize can safely be allowed to default to the largest values supported by both client and server,independent of the network' s= mtu=
Using the mountproto mount option This section applies only to NFS version 2 and version 3 mounts since NFS version 4 does not use a separate protocol for mount requests.
The Linux NFS client can use a different transport for contacting an NFS server's rpcbind service, its mountd service, its Network Lock Manager (NLM)service, and its NFS service. The exact transports employed by the Linux NFS client for each mount point depends on the settings of the transport mountoptions, which include proto , mountproto , udp , and tcp .
The client sends Network Status Manager (NSM) notifications via UDP no matter what transport options are specified, but listens for server NSM notificationson both UDP and TCP. The NFS Access Control List (NFSACL) protocol shares the same transport as the main NFS service.
If no transport options are specified, the Linux NFS client uses UDP to contact the server's mountd service, and TCP to contact its NLM and NFS services bydefault.
If the server does not support these transports for these services, the mount (8) command attempts to discover what the server supports, and thenretries the mount request once using the discovered transports. If the server does not advertise any transport supported by the client or is misconfigured, themount request fails. If the bg option is in effect, the mount command backgrounds itself and continues to attempt the specified mount request.
When the proto option, the udp option, or the tcp option is specified but the mountproto option is not, the specified transportis used to contact both the server's mountd service and for the NLM and NFS services.
If the mountproto option is specified but none of the proto , udp or tcp options are specified, then the specified transport isused for the initial mountd request, but the mount command attempts to discover what the server supports for the NFS protocol, preferring TCP if bothtransports are supported.
If both the mountproto and proto (or udp or tcp ) options are specified, then the transport specified by the mountproto option is used for the initial mountd request, and the transport specified by the proto option (or the udp or tcp options) is used forNFS, no matter what order these options appear. No automatic service discovery is performed if these options are specified.
If any of the proto , udp , tcp , or mountproto options are specified more than once on the same mount command line, then the valueof the rightmost instance of each of these options takes effect. Data And Metadata Coherence
Some modern cluster file systems provide perfect cache coherence among their clients. Perfect cache coherence among disparate NFS clients is expensive toachieve, especially on wide area networks. As such, NFS settles for weaker cache coherence that satisfies the requirements of most file sharing types.Normally, file sharing is completely sequential: first client A opens a file, writes something to it, then closes it; then client B opens the same file, andreads the changes.
Close-to-open cache consistency When an application opens a file stored on an NFS server, the NFS client checks that it still exists on the server and is permitted to the opener by sendinga GETATTR or ACCESS request. When the application closes the file, the NFS client writes back any pending changes to the file so that the next opener can viewthe changes. This also gives the NFS client an opportunity to report any server write errors to the application via the return code from close (2). Thebehavior of checking at open time and flushing at close time is referred to as close-to-open cache consistency.
Weak cache consistency There are still opportunities for a client' s= data= cache= to= contain= stale= data.= the= nfs= version= 3= protocol= introduced= 'weak= cache= consistency'= (also= known= aswcc)= which= provides= a= way= of= efficiently= checking= a= file's= attributes= before= and= after= a= single= request.= this= allows= a= client= to= help= identify= changes= thatcould= have= been= made= by= other=
When a client is using many concurrent operations that update the same file at the same time (for example, during asynchronous write behind), it is stilldifficult to tell whether it was that client's updates or some other client's updates that altered the file.
Attribute caching Use the noac mount option to achieve attribute cache coherence among multiple clients. Almost every file system operation checks file attributeinformation. The client keeps this information cached for a period of time to reduce network and server load. When noac is in effect, a client's fileattribute cache is disabled, so each operation that needs to check a file's attributes is forced to go back to the server. This permits a client to see changesto a file very quickly, at the cost of many extra network operations.
Be careful not to confuse the noac option with 'no data caching.' The noac mount option prevents the client from caching file metadata, butthere are still races that may result in data cache incoherence between client and server.
The NFS protocol is not designed to support true cluster file system cache coherence without some type of application serialization. If absolute cachecoherence among clients is required, applications should use file locking. Alternatively, applications can also open their files with the O_DIRECT flag todisable data caching entirely.
Directory entry caching The Linux NFS client caches the result of all NFS LOOKUP requests. If the requested directory entry exists on the server, the result is referred to as a positive lookup result. If the requested directory entry does not exist on the server (that is, the server returned ENOENT), the result is referred toas negative lookup result.
To detect when directory entries have been added or removed on the server, the Linux NFS client watches a directory's mtime. If the client detects a changein a directory's mtime, the client drops all cached LOOKUP results for that directory. Since the directory's mtime is a cached attribute, it may take some timebefore a client notices it has changed. See the descriptions of the acdirmin , acdirmax , and noac mount options for more information abouthow long a directory's mtime is cached.
Caching directory entries improves the performance of applications that do not share files with applications on other clients. Using cached informationabout directories can interfere with applications that run concurrently on multiple clients and need to detect the creation or removal of files quickly,however. The lookupcache mount option allows some tuning of directory entry caching behavior.
Before kernel release 2.6.28, the Linux NFS client tracked only positive lookup results. This permitted applications to detect new directory entries createdby other clients quickly while still providing some of the performance benefits of caching. If an application depends on the previous lookup caching behaviorof the Linux NFS client, you can use lookupcache=positive .
If the client ignores its cache and validates every application lookup request with the server, that client can immediately detect when a new directoryentry has been either created or removed by another client. You can specify this behavior using lookupcache=none . The extra NFS requests needed if theclient does not cache directory entries can exact a performance penalty. Disabling lookup caching should result in less of a performance penalty than using noac , and has no effect on how the NFS client caches the attributes of files. Mac Read Ntfs
The sync mount option The NFS client treats the sync mount option differently than some other file systems (refer to mount (8) for a description of the generic sync and async mount options). If neither sync nor async is specified (or if the async option is specified), the NFS clientdelays sending application writes to the server until any of these events occur: Memory pressure forces reclamation of system memory resources.
An application flushes file data explicitly with sync (2), msync (2), or fsync (3).
An application closes a file with close (2).
The file is locked/unlocked via fcntl (2). In other words, under normal circumstances, data written by an application may not immediately appear on the server that hosts the file.
If the sync option is specified on a mount point, any system call that writes data to files on that mount point causes that data to be flushed to theserver before the system call returns control to user space. This provides greater data cache coherence among clients, but at a significant performance cost.
Applications can use the O_SYNC open flag to force application writes to individual files to go to the server immediately without the use of the sync mount option.
Using file locks with NFS The Network Lock Manager protocol is a separate sideband protocol used to manage file locks in NFS version 2 and version 3. To support lock recovery after aclient or server reboot, a second sideband protocol -- known as the Network Status Manager protocol -- is also required. In NFS version 4, file locking issupported directly in the main NFS protocol, and the NLM and NSM sideband protocols are not used.
In most cases, NLM and NSM services are started automatically, and no extra configuration is required. Configure all NFS clients with fully-qualified domainnames to ensure that NFS servers can find clients to notify them of server reboots.
NLM supports advisory file locks only. To lock NFS files, use fcntl (2) with the F_GETLK and F_SETLK commands. The NFS client converts file locksobtained via flock (2) to advisory locks.
When mounting servers that do not support the NLM protocol, or when mounting an NFS server through a firewall that blocks the NLM service port, specify the nolock mount option. NLM locking must be disabled with the nolock option when using NFS to mount /var because /var contains filesused by the NLM implementation on Linux.
Specifying the nolock option may also be advised to improve the performance of a proprietary application which runs on a single client and uses filelocks extensively.
NFS version 4 caching features The data and metadata caching behavior of NFS version 4 clients is similar to that of earlier versions. However, NFS version 4 adds two features thatimprove cache behavior: change attributes and file delegation .
The change attribute is a new part of NFS file and directory metadata which tracks data changes. It replaces the use of a file's modification andchange time stamps as a way for clients to validate the content of their caches. Change attributes are independent of the time stamp resolution on either theserver or client, however.
A file delegation is a contract between an NFS version 4 client and server that allows the client to treat a file temporarily as if no other clientis accessing it. The server promises to notify the client (via a callback request) if another client attempts to access that file. Once a file has beendelegated to a client, the client can cache that file's data and metadata aggressively without contacting the server.
File delegations come in two flavors: read and write . A read delegation means that the server notifies the client about any otherclients that want to write to the file. A write delegation means that the client gets notified about either read or write accessors.
Servers grant file delegations when a file is opened, and can recall delegations at any time when another client wants access to the file that conflictswith any delegations already granted. Delegations on directories are not supported.
In order to support delegation callback, the server checks the network return path to the client during the client's initial contact with the server. Ifcontact with the client cannot be established, the server simply does not grant any delegations to that client. Security Considerations
NFS servers control access to file data, but they depend on their RPC implementation to provide authentication of NFS requests. Traditional NFS accesscontrol mimics the standard mode bit access control provided in local file systems. Traditional RPC authentication uses a number to represent each user(usually the user's own uid), a number to represent the user's group (the user's gid), and a set of up to 16 auxiliary group numbers to represent other groupsof which the user may be a member.
Typically, file data and user ID values appear unencrypted (i.e. 'in the clear') on the network. Moreover, NFS versions 2 and 3 use separate sidebandprotocols for mounting, locking and unlocking files, and reporting system status of clients and servers. These auxiliary protocols use no authentication.
In addition to combining these sideband protocols with the main NFS protocol, NFS version 4 introduces more advanced forms of access control,authentication, and in-transit data protection. The NFS version 4 specification mandates NFSv4 ACLs, RPCGSS authentication, and RPCGSS security flavors thatprovide per-RPC integrity checking and encryption. Because NFS version 4 combines the function of the sideband protocols into the main NFS protocol, the newsecurity features apply to all NFS version 4 operations including mounting, file locking, and so on. RPCGSS authentication can also be used with NFS versions 2and 3, but does not protect their sideband protocols.
The sec mount option specifies the RPCGSS security mode that is in effect on a given NFS mount point. Specifying sec=krb5 providescryptographic proof of a user's identity in each RPC request. This provides strong verification of the identity of users accessing data on the server. Notethat additional configuration besides adding this mount option is required in order to enable Kerberos security. Refer to the rpc.gssd (8) man page fordetails.
Two additional flavors of Kerberos security are supported: krb5i and krb5p . The krb5i security flavor provides a cryptographicallystrong guarantee that the data in each RPC request has not been tampered with. The krb5p security flavor encrypts every RPC request to prevent dataexposure during network transit; however, expect some performance impact when using integrity checking or encryption. Similar support for other forms ofcryptographic security (such as lipkey and SPKM3) is also available.
The NFS version 4 protocol allows clients and servers to negotiate among multiple security flavors during mount processing. However, Linux does not yetimplement such negotiation. The Linux client specifies a single security flavor at mount time which remains in effect for the lifetime of the mount. If theserver does not support this flavor, the initial mount request is rejected by the server.
Using non-privileged source ports NFS clients usually communicate with NFS servers via network sockets. Each end of a socket is assigned a port value, which is simply a number between 1 and65535 that distinguishes socket endpoints at the same IP address. A socket is uniquely defined by a tuple that includes the transport protocol (TCP or UDP) andthe port values and IP addresses of both endpoints.
The NFS client can choose any source port value for its sockets, but usually chooses a privileged port. A privileged port is a port value less than1024. Only a process with root privileges may create a socket with a privileged source port.
The exact range of privileged source ports that can be chosen is set by a pair of sysctls to avoid choosing a well-known port, such as the port used by ssh.This means the number of source ports available for the NFS client, and therefore the number of socket connections that can be used at the same time, ispractically limited to only a few hundred.
As described above, the traditional default NFS authentication scheme, known as AUTH_SYS, relies on sending local UID and GID numbers to identify usersmaking NFS requests. An NFS server assumes that if a connection comes from a privileged port, the UID and GID numbers in the NFS requests on this connectionhave been verified by the client's kernel or some other local authority. This is an easy system to spoof, but on a trusted physical network between trustedhosts, it is entirely adequate.
Roughly speaking, one socket is used for each NFS mount point. If a client could use non-privileged source ports as well, the number of sockets allowed, andthus the maximum number of concurrent mount points, would be much larger.
Using non-privileged source ports may compromise server security somewhat, since any user on AUTH_SYS mount points can now pretend to be any other whenmaking NFS requests. Thus NFS servers do not support this by default. They explicitly allow it usually via an export option.
To retain good security while allowing as many mount points as possible, it is best to allow non-privileged client connections only if the server and clientboth require strong authentication, such as Kerberos.
Mounting through a firewall A firewall may reside between an NFS client and server, or the client or server may block some of its own ports via IP filter rules. It is still possible tomount an NFS server through a firewall, though some of the mount (8) command's automatic service endpoint discovery mechanisms may not work; thisrequires you to provide specific endpoint details via NFS mount options.
NFS servers normally run a portmapper or rpcbind daemon to advertise their service endpoints to clients. Clients use the rpcbind daemon todetermine: What network port each RPC-based service is using
What transport protocols each RPC-based service supports The rpcbind daemon uses a well-known port number (111) to help clients find a service endpoint. Although NFS often uses a standard port number (2049),auxiliary services such as the NLM service can choose any unused port number at random.
Common firewall configurations block the well-known rpcbind port. In the absense of an rpcbind service, the server administrator fixes the port number ofNFS-related services so that the firewall can allow access to specific NFS service ports. Client administrators then specify the port number for the mountdservice via the mount (8) command's mountport option. It may also be necessary to enforce the use of TCP or UDP if the firewall blocks one ofthose transports.
NFS Access Control Lists Solaris allows NFS version 3 clients direct access to POSIX Access Control Lists stored in its local file systems. This proprietary sideband protocol, knownas NFSACL, provides richer access control than mode bits. Linux implements this protocol for compatibility with the Solaris NFS implementation. The NFSACLprotocol never became a standard part of the NFS version 3 specification, however.
The NFS version 4 specification mandates a new version of Access Control Lists that are semantically richer than POSIX ACLs. NFS version 4 ACLs are notfully compatible with POSIX ACLs; as such, some translation between the two is required in an environment that mixes POSIX ACLs and NFS version4. The Remount Option
Generic mount options such as rw and sync can be modified on NFS mount points using the remount option. See mount (8) for moreinformation on generic mount options.
With few exceptions, NFS-specific options are not able to be modified during a remount. The underlying transport or NFS version cannot be changed by aremount, for example.
Performing a remount on an NFS file system mounted with the noac option may have unintended consequences. The noac option is a combination ofthe generic option sync , and the NFS-specific option actimeo=0 .
Unmounting after a remount For mount points that use NFS versions 2 or 3, the NFS umount subcommand depends on knowing the original set of mount options used to perform the MNToperation. These options are stored on disk by the NFS mount subcommand, and can be erased by a remount.
To ensure that the saved mount options are not erased during a remount, specify either the local mount directory, or the server hostname and exportpathname, but not both, during a remount. For example, mount -o remount,ro /mnt merges the mount option ro with the mount options already saved on disk for the NFS server mounted at /mnt. Files /etc/fstab
file system table Bugs
Before 2.4.7, the Linux NFS client did not support NFS over TCP.
Before 2.4.20, the Linux NFS client used a heuristic to determine whether cached file data was still valid rather than using the standard close-to-opencache coherency method described above.
Starting with 2.4.22, the Linux NFS client employs a Van Jacobsen-based RTT estimator to determine retransmit timeout values when using NFS over UDP.
Before 2.6.0, the Linux NFS client did not support NFS version 4.
Before 2.6.8, the Linux NFS client used only synchronous reads and writes when the rsize and wsize settings were smaller than the system'spage size.
The Linux NFS client does not yet support certain optional features of the NFS version 4 protocol, such as security negotiation, server referrals, and namedattributes. See Also
fstab (5), mount (8), umount (8), mount.nfs (5), umount.nfs (5), exports (5), netconfig (5), ipv6 (7), nfsd (8), sm-notify (8), rpc.statd (8), rpc.idmapd (8), rpc.gssd (8), rpc.svcgssd (8), kerberos (1)
RFC 768 for the UDP specification.
RFC 793 for the TCP specification.
RFC 1094 for the NFS version 2 specification.
RFC 1813 for the NFS version 3 specification.
RFC 1832 for the XDR specification.
RFC 1833 for the RPC bind specification.
RFC 2203 for the RPCSEC GSS API protocol specification.
RFC 3530 for the NFS version 4 specification. Referenced By Ntfs For Mac Download mount.nfs (8), mountd (8), nfsstat Linux Nfs For Mac Windows 7 (8), rpc.rquotad (8), rpcdebug (8), umount.nfs4 (8)
