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32 .Nd NFS Version 4 Protocol
34 The NFS client and server provides support for the
37 .%T "Network File System (NFS) Version 4 Protocol RFC 3530" .
38 The protocol is somewhat similar to NFS Version 3, but differs in significant
40 It uses a single compound RPC that concatenates operations to-gether.
41 Each of these operations are similar to the RPCs of NFS Version 3.
42 The operations in the compound are performed in order, until one of
43 them fails (returns an error) and then the RPC terminates at that point.
46 integrated locking support, which implies that the server is no longer
50 server remains in recovery mode for a grace period (always greater than the
51 lease duration the server uses) after a reboot.
52 During this grace period, clients may recover state but not perform other
53 open/lock state changing operations.
54 To provide for correct recovery semantics, a small file described by
56 is used by the server during the recovery phase.
57 If this file is missing or empty, there is a backup copy maintained by
59 that will be used. If either file is missing, they will be
62 If both the file and the backup copy are empty,
63 it will result in the server starting without providing a grace period
65 Note that recovery only occurs when the server
66 machine is rebooted, not when the
70 It provides several optional features not present in NFS Version 3:
72 .Bd -literal -offset indent -compact
74 - Referrals, which redirect subtrees to other servers
76 - Delegations, which allow a client to operate on a file locally
81 protocol does not use a separate mount protocol and assumes that the
82 server provides a single file system tree structure, rooted at the point
83 in the local file system tree specified by one or more
85 .Bd -literal -offset indent -compact
86 V4: <rootdir> [-sec=secflavors] [host(s) or net]
97 allows a limited subset of operations to be performed on non-exported subtrees
98 of the local file system, so that traversal of the tree to the exported
100 As such, the ``<rootdir>'' can be in a non-exported file system.
102 the entire tree that is rooted at that point must be in local file systems
103 that are of types that can be NFS exported.
106 file system is rooted at ``<rootdir>'', setting this to anything other
107 than ``/'' will result in clients being required to use different mount
110 than for NFS Version 2 or 3.
111 Unlike NFS Version 2 and 3, Version 4 allows a client mount to span across
112 multiple server file systems, although not all clients are capable of doing
116 uses names for users and groups instead of numbers.
120 .Bd -literal -offset indent -compact
124 where ``<dns.domain>'' is not the same as the DNS domain used
125 for host name lookups, but is usually set to the same string.
126 Most systems set this ``<dns.domain>''
127 to the domain name part of the machine's
130 However, this can normally be overridden by a command line
131 option or configuration file for the daemon used to do the name<->number
133 Under FreeBSD, the mapping daemon is called
135 and has a command line option that overrides the domain component of the
139 either client or server, this daemon must be running.
140 If this ``<dns.domain>'' is not set correctly or the daemon is not running, ``ls -l'' will typically
141 report a lot of ``nobody'' and ``nogroup'' ownerships.
143 Although uid/gid numbers are no longer used in the
145 protocol, they will still be in the RPC authentication fields when
146 using AUTH_SYS (sec=sys), which is the default.
147 As such, in this case both the user/group name and number spaces must
148 be consistent between the client and server.
152 with RPCSEC_GSS (sec=krb5, krb5i, krb5p), only names and KerberosV tickets
156 To set up the NFS server that supports
158 you will need to either set the variables in
162 .Bd -literal -offset indent -compact
163 nfs_server_enable="YES"
164 nfsv4_server_enable="YES"
165 nfsuserd_enable="YES"
172 without the ``-o'' option, which would force use of the old server.
175 daemon must also be running.
177 You will also need to add at least one ``V4:'' line to the
183 If the file systems you are exporting are only being accessed via
185 there are a couple of
187 variables that you can change, which might improve performance.
189 .It Cm vfs.nfsd.issue_delegations
190 when set non-zero, allows the server to issue Open Delegations to
192 These delegations permit the client to manipulate the file
193 locally on the client.
194 Unfortunately, at this time, client use of
195 delegations is limited, so performance gains may not be observed.
196 This can only be enabled when the file systems being exported to
198 clients are not being accessed locally on the server and, if being
199 accessed via NFS Version 2 or 3 clients, these clients cannot be
201 .It Cm vfs.nfsd.enable_locallocks
202 can be set to 0 to disable acquisition of local byte range locks.
203 Disabling local locking can only be done if neither local accesses
204 to the exported file systems nor the NLM is operating on them.
207 Note that Samba server access would be considered ``local access'' for the above
210 To build a kernel with the NFS server that supports
214 .Bd -literal -offset indent -compact
218 must be specified in the kernel's
225 mount, specify the ``nfsv4'' option on the
228 This will force use of the client that supports
235 must be running, as above.
238 server that is being mounted on supports delegations, you can start the
240 daemon to handle client side callbacks.
243 .Bd -literal -offset indent -compact
244 nfsuserd_enable="YES"
251 Without a functioning callback path, a server will never issue Delegations
254 By default, the callback address will be set to the IP address acquired via
255 rtalloc() in the kernel and port# 7745.
256 To override the default port#, a command line option for
260 To get callbacks to work when behind a NAT gateway, a port for the callback
261 service will need to be set up on the NAT gateway and then the address
262 of the NAT gateway (host IP plus port#) will need to be set by assigning the
264 variable vfs.nfs.callback_addr to a string of the form:
268 where the first 4 Ns are the host IP address and the last two are the
269 port# in network byte order (all decimal #s in the range 0-255).
271 To build a kernel with the client that supports
273 linked into it, the option
275 .Bd -literal -offset indent -compact
279 must be specified in the kernel's
283 Options can be specified for the
287 daemons at boot time via the ``nfsuserd_flags'' and ``nfscbd_flags''
291 .Bl -tag -width /var/db/nfs-stablerestart.bak -compact
292 .It Pa /var/db/nfs-stablerestart
293 NFS V4 stable restart file
294 .It Pa /var/db/nfs-stablerestart.bak
295 backup copy of the file
298 .Xr stablerestart 5 ,
306 At this time, there is no recall of delegations for local file system
308 As such, delegations should only be enabled for file systems
309 that are being used solely as NFS export volumes and are not being accessed
310 via local system calls nor services such as Samba.