.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 after
-60 seconds for NFS over TCP, and are retried after 7/10 of a second for
-NFS over UDP.
+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.
.IP
-For NFS over TCP, the client uses a fixed timeout, as specified by the
-.B timeo
-option. However, for NFS over UDP, the client uses an adaptive
+However, for NFS over UDP, the client uses an adaptive
algorithm to estimate an appropriate timeout value for frequently used
request types (such as READ and WRITE requests), but uses the
.B timeo
setting for infrequently used request types (such as FSINFO requests).
-After each retransmission, the NFS client doubles the timeout for that
-request, up to a maximum timeout length of 60 seconds.
+If the
+.B timeo
+option is not specified,
+infrequently used request types are retried after 1.1 seconds.
+After each retransmission, the NFS client doubles the timeout for
+that request,
+up to a maximum timeout length of 60 seconds.
.TP 1.5i
.BI retrans= n
The number of times the NFS client retries a request before
it attempts further recovery action. If the
.B retrans
-option is not specified, the NFS client retries each request
+option is not specified, the NFS client tries each request
three times.
.IP
The NFS client generates a "server not responding" message
.B nfs
file system type.
.TP 1.5i
-.BI proto= netid
-The transport protocol used by the NFS client
+.BI proto= transport
+The transport the NFS client uses
to transmit requests to the NFS server for this mount point.
-.I netid
+.I transport
can be either
.B udp
or
.BR tcp .
-Each transport protocol uses different default
+Each transport uses different default
.B retrans
and
.B timeo
This option can be used when mounting an NFS server
through a firewall that blocks the rpcbind protocol.
.TP 1.5i
+.BI mountproto= transport
+The transport the NFS client uses
+to transmit requests to the NFS server's mountd service when performing
+this mount request, and when later unmounting this mount point.
+.I transport
+can be either
+.B udp
+or
+.BR tcp .
+.IP
+This option can be used when mounting an NFS server
+through a firewall that blocks a particular transport.
+When used in combination with the
+.B proto
+option, different transports for mountd requests and NFS requests
+can be specified.
+If the server's mountd service is not available via the specified
+transport, the mount request fails.
+Refer to the TRANSPORT METHODS section for more on how the
+.B mountproto
+mount option interacts with the
+.B proto
+mount option.
+.TP 1.5i
.BI mounthost= name
The hostname of the host running mountd.
If this option is not specified, the
.B nfs4
file system type.
.TP 1.5i
-.BI proto= netid
-The transport protocol used by the NFS client
+.BI proto= transport
+The transport the NFS client uses
to transmit requests to the NFS server for this mount point.
-.I netid
+.I transport
can be either
.B udp
or
.B wsize
can safely be allowed to default to the largest values supported by
both client and server, independent of the network's MTU size.
+.SS "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.
+.P
+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
+mount options, which include
+.BR proto ,
+.BR mountproto ,
+.BR udp ", and " tcp .
+.P
+The client sends Network Status Manager (NSM) notifications
+via UDP no matter what transport options are specified, but
+listens for server NSM notifications on both UDP and TCP.
+The NFS Access Control List (NFSACL) protocol shares the same
+transport as the main NFS service.
+.P
+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 by default.
+.P
+If the server does not support these transports for these services, the
+.BR mount (8)
+command attempts to discover what the server supports, and then retries
+the mount request once using the discovered transports.
+If the server does not advertise any transport supported by the client
+or is misconfigured, the mount request fails.
+If the
+.B bg
+option is in effect, the mount command backgrounds itself and continues
+to attempt the specified mount request.
+.P
+When the
+.B proto
+option, the
+.B udp
+option, or the
+.B tcp
+option is specified but the
+.B mountproto
+option is not, the specified transport is used to contact
+both the server's mountd service and for the NLM and NFS services.
+.P
+If the
+.B mountproto
+option is specified but none of the
+.BR proto ", " udp " or " tcp
+options are specified, then the specified transport is used for the
+initial mountd request, but the mount command attempts to discover
+what the server supports for the NFS protocol, preferring TCP if
+both transports are supported.
+.P
+If both the
+.BR mountproto " and " proto
+(or
+.BR udp " or " tcp )
+options are specified, then the transport specified by the
+.B mountproto
+option is used for the initial mountd request, and the transport
+specified by the
+.B proto
+option (or the
+.BR udp " or " tcp " options)"
+is used for NFS, no matter what order these options appear.
+No automatic service discovery is performed if these options are
+specified.
+.P
+If any of the
+.BR proto ", " udp ", " tcp ", "
+or
+.B mountproto
+options are specified more than once on the same mount command line,
+then the value of the rightmost instance of each of these options
+takes effect.
.SH "DATA AND METADATA COHERENCE"
Some modern cluster file systems provide
perfect cache coherence among their clients.
.BR umount.nfs (5),
.BR exports (5),
.BR nfsd (8),
+.BR sm-notify (8),
+.BR rpc.statd (8),
.BR rpc.idmapd (8),
.BR rpc.gssd (8),
.BR rpc.svcgssd (8),
projects / nfs-utils.git / blobdiff