.SH NAME
nfs \- fstab format and options for the
.B nfs
-and
-.B nfs4
file systems
.SH SYNOPSIS
.I /etc/fstab
The fifth and sixth fields on each line are not used
by NFS, thus conventionally each contain the digit zero. For example:
.P
-.SP
-.NF
-.TA 2.5i +0.75i +0.75i +1.0i
+.nf
+.ta 8n +14n +14n +9n +20n
server:path /mountpoint fstype option,option,... 0 0
-.FI
+.fi
.P
The server's hostname and export pathname
are separated by a colon, while
.P
The
.I fstype
-field contains either "nfs" (for version 2 or version 3 NFS mounts)
-or "nfs4" (for NFS version 4 mounts).
-The
-.B nfs
-and
-.B nfs4
-file system types share similar mount options,
-which are described below.
+field contains "nfs". Use of the "nfs4" fstype in
+.I /etc/fstab
+is deprecated.
.SH "MOUNT OPTIONS"
Refer to
.BR mount (8)
in
.IR /etc/fstab .
.DT
-.SS "Valid options for either the nfs or nfs4 file system type"
-These options are valid to use when mounting either
-.B nfs
-or
-.B nfs4
-file system types.
-They imply the same behavior
-and have the same default for both file system types.
+.SS "Options supported by all versions"
+These options are valid to use with any NFS version.
.TP 1.5i
.BR soft " / " hard
Determines the recovery behavior of the NFS client
option.
.TP 1.5i
.BI timeo= n
-The time (in tenths of a second) the NFS client waits for a
-response before it retries an NFS request. If this
-option is not specified, requests are retried every
-60 seconds for NFS over TCP.
-The NFS client does not perform any kind of timeout backoff
-for NFS over TCP.
+The time in deciseconds (tenths of a second) the NFS client waits for a
+response before it retries an NFS request.
+.IP
+For NFS over TCP the default
+.B timeo
+value is 600 (60 seconds).
+The NFS client performs linear backoff: After each retransmission the
+timeout is increased by
+.BR timeo
+up to the maximum of 600 seconds.
.IP
However, for NFS over UDP, the client uses an adaptive
algorithm to estimate an appropriate timeout value for frequently used
command retries an NFS mount operation
in the foreground or background before giving up.
If this option is not 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).
+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
+.BR mount (8)
+command exits immediately after the first failure.
.TP 1.5i
.BI sec= mode
The RPCGSS security flavor to use for accessing files on this mount point.
.IP
The DATA AND METADATA COHERENCE section contains a
detailed discussion of these trade-offs.
-.SS "Valid options for the nfs file system type"
+.SS "Options for NFS versions 2 and 3 only"
Use these options, along with the options in the above subsection,
-for mounting the
-.B nfs
-file system type.
+for NFS versions 2 and 3 only.
.TP 1.5i
.BI proto= netid
The transport protocol name and protocol family the NFS client uses
.I netid
is a valid netid listed in
.IR /etc/netconfig .
-Otherwise,
+The value "rdma" may also be specified.
+If the
+.B mount.nfs
+command does not have TI-RPC support, then
.I netid
is one of "tcp," "udp," or "rdma," and only IPv4 may be used.
.IP
.BR proto=tcp.
It is included for compatibility with other operating systems.
.TP 1.5i
+.B rdma
+The
+.B rdma
+option is an alternative to specifying
+.BR proto=rdma.
+.TP 1.5i
.BI 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,
.TP 1.5i
.BI nfsvers= n
The NFS protocol version number used to contact the server's NFS service.
-The Linux client supports version 2 and version 3 of the NFS protocol
-when using the file system type
-.BR nfs .
-If the server does not support the requested version,
-the mount request fails.
-If this option is not specified, the client attempts to use version 3,
-but negotiates the NFS version with the server if version 3 support
-is not available.
+If the server does not support the requested version, the mount request fails.
+If this option is not specified, the client negotiates a suitable version with
+the server, trying version 4 first, version 3 second, and version 2 last.
.TP 1.5i
.BI vers= n
This option is an alternative to the
on NFS version 3 mounts to read small directories.
Some applications perform better if the client uses only READDIR requests
for all directories.
-.SS "Valid options for the nfs4 file system type"
+.TP 1.5i
+.BR local_lock= mechanism
+Specifies whether to use local locking for any or both of the flock and the
+POSIX locking mechanisms.
+.I mechanism
+can be one of
+.BR all ,
+.BR flock ,
+.BR posix ,
+or
+.BR none .
+This option is supported in kernels 2.6.37 and later.
+.IP
+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
+other applications running on the same client. Remote applications are not
+affected by these locks.
+.IP
+If this option is not specified, or if
+.B none
+is specified, the client assumes that the locks are not local.
+.IP
+If
+.BR all
+is specified, the client assumes that both flock and POSIX locks are local.
+.IP
+If
+.BR 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.
+.IP
+If
+.BR posix
+is specified, the client assumes that POSIX locks are local and uses NLM
+sideband protocol to lock files when flock locks are used.
+.IP
+To support legacy flock behavior similar to that of NFS clients < 2.6.12,
+use 'local_lock=flock'. This option is required when exporting NFS mounts via
+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.
+.IP
+NOTE: When used together, the 'local_lock' mount option will be overridden
+by 'nolock'/'lock' mount option.
+.SS "Options for NFS version 4 only"
Use these options, along with the options in the first subsection above,
-for mounting the
-.B nfs4
-file system type.
+for NFS version 4 and newer.
.TP 1.5i
.BI proto= netid
The transport protocol name and protocol family the NFS client uses
special routing policies,
or atypical network topologies,
the exact address to use for callbacks may be nontrivial to determine.
+.SH nfs4 FILE SYSTEM TYPE
+The
+.BR 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
+.B nfsvers
+mount option.
.SH 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
.B nfsvers=3
mount option.
To mount using NFS version 4,
-use the
-.B nfs4
-file system type.
-The
-.B nfsvers
-mount option is not supported for the
+use either the
+.B nfs
+file system type, with the
+.B nfsvers=4
+mount option, or the
.B nfs4
file system type.
.P
file causes the mount command to negotiate
reasonable defaults for NFS behavior.
.P
-.NF
-.TA 2.5i +0.7i +0.7i +.7i
+.nf
+.ta 8n +16n +6n +6n +30n
server:/export /mnt nfs defaults 0 0
-.FI
+.fi
.P
Here is an example from an /etc/fstab file for an NFS version 2 mount over UDP.
.P
-.NF
-.TA 2.5i +0.7i +0.7i +.7i
+.nf
+.ta 8n +16n +6n +6n +30n
server:/export /mnt nfs nfsvers=2,proto=udp 0 0
-.FI
+.fi
.P
Try this example to mount using NFS version 4 over TCP
with Kerberos 5 mutual authentication.
.P
-.NF
-.TA 2.5i +0.7i +0.7i +.7i
+.nf
+.ta 8n +16n +6n +6n +30n
server:/export /mnt nfs4 sec=krb5 0 0
-.FI
+.fi
.P
This example can be used to mount /usr over NFS.
.P
-.NF
-.TA 2.5i +0.7i +0.7i +.7i
+.nf
+.ta 8n +16n +6n +6n +30n
server:/export /usr nfs ro,nolock,nocto,actimeo=3600 0 0
-.FI
+.fi
.P
This example shows how to mount an NFS server
using a raw IPv6 link-local address.
.P
-.NF
-.TA 2.5i +0.7i +0.7i +.7i
+.nf
+.ta 8n +40n +5n +4n +9n
[fe80::215:c5ff:fb3e:e2b1%eth0]:/export /mnt nfs defaults 0 0
-.FI
+.fi
.SH "TRANSPORT METHODS"
NFS clients send requests to NFS servers via
Remote Procedure Calls, or
NFS version 4 ACLs are not fully compatible with POSIX ACLs; as such,
some translation between the two is required
in an environment that mixes POSIX ACLs and NFS version 4.
-.SH FILES
-.TP 1.5i
-.I /etc/fstab
-file system table
-.SH BUGS
-The generic
-.B remount
-option is not fully supported.
-Generic options, such as
-.BR rw " and " ro
-can be modified using the
-.B remount
-option,
-but NFS-specific options are not all supported.
+.SH "THE REMOUNT OPTION"
+Generic mount options such as
+.BR rw " and " sync
+can be modified on NFS mount points using the
+.BR remount
+option.
+See
+.BR mount (8)
+for more information on generic mount options.
+.P
+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 a remount, for example.
+.P
Performing a remount on an NFS file system mounted with the
.B noac
option may have unintended consequences.
The
.B noac
-option is a mixture of a generic option,
+option is a combination of the generic option
.BR sync ,
-and an NFS-specific option
+and the NFS-specific option
.BR actimeo=0 .
+.SS "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
+MNT operation.
+These options are stored on disk by the NFS mount subcommand,
+and can be erased by a remount.
+.P
+To ensure that the saved mount options are not erased during a remount,
+specify either the local mount directory, or the server hostname and
+export pathname, but not both, during a remount. For example,
+.P
+.NF
+.TA 2.5i
+ mount -o remount,ro /mnt
+.FI
.P
+merges the mount option
+.B ro
+with the mount options already saved on disk for the NFS server mounted at /mnt.
+.SH FILES
+.TP 1.5i
+.I /etc/fstab
+file system table
+.SH BUGS
Before 2.4.7, the Linux NFS client did not support NFS over TCP.
.P
Before 2.4.20, the Linux NFS client used a heuristic
projects / nfs-utils.git / blobdiff