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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.
101 The exception is ZFS, which checks exports and, as such, all ZFS file systems
102 below the ``<rootdir>'' must be exported.
104 the entire tree that is rooted at that point must be in local file systems
105 that are of types that can be NFS exported.
108 file system is rooted at ``<rootdir>'', setting this to anything other
109 than ``/'' will result in clients being required to use different mount
112 than for NFS Version 2 or 3.
113 Unlike NFS Version 2 and 3, Version 4 allows a client mount to span across
114 multiple server file systems, although not all clients are capable of doing
118 uses names for users and groups instead of numbers.
122 .Bd -literal -offset indent -compact
126 where ``<dns.domain>'' is not the same as the DNS domain used
127 for host name lookups, but is usually set to the same string.
128 Most systems set this ``<dns.domain>''
129 to the domain name part of the machine's
132 However, this can normally be overridden by a command line
133 option or configuration file for the daemon used to do the name<->number
135 Under FreeBSD, the mapping daemon is called
137 and has a command line option that overrides the domain component of the
141 either client or server, this daemon must be running.
142 If this ``<dns.domain>'' is not set correctly or the daemon is not running, ``ls -l'' will typically
143 report a lot of ``nobody'' and ``nogroup'' ownerships.
145 Although uid/gid numbers are no longer used in the
147 protocol, they will still be in the RPC authentication fields when
148 using AUTH_SYS (sec=sys), which is the default.
149 As such, in this case both the user/group name and number spaces must
150 be consistent between the client and server.
154 with RPCSEC_GSS (sec=krb5, krb5i, krb5p), only names and KerberosV tickets
157 To set up the NFS server that supports
159 you will need to either set the variables in
163 .Bd -literal -offset indent -compact
164 nfs_server_enable="YES"
165 nfsv4_server_enable="YES"
166 nfsuserd_enable="YES"
173 without the ``-o'' option, which would force use of the old server.
176 daemon must also be running.
178 You will also need to add at least one ``V4:'' line to the
184 If the file systems you are exporting are only being accessed via
186 there are a couple of
188 variables that you can change, which might improve performance.
190 .It Cm vfs.nfsd.issue_delegations
191 when set non-zero, allows the server to issue Open Delegations to
193 These delegations permit the client to manipulate the file
194 locally on the client.
195 Unfortunately, at this time, client use of
196 delegations is limited, so performance gains may not be observed.
197 This can only be enabled when the file systems being exported to
199 clients are not being accessed locally on the server and, if being
200 accessed via NFS Version 2 or 3 clients, these clients cannot be
202 .It Cm vfs.nfsd.enable_locallocks
203 can be set to 0 to disable acquisition of local byte range locks.
204 Disabling local locking can only be done if neither local accesses
205 to the exported file systems nor the NLM is operating on them.
208 Note that Samba server access would be considered ``local access'' for the above
211 To build a kernel with the NFS server that supports
215 .Bd -literal -offset indent -compact
219 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 mount uses the host uuid to identify the client uniquely to the server,
239 you cannot safely do an
243 .Bd -literal -offset indent -compact
252 server that is being mounted on supports delegations, you can start the
254 daemon to handle client side callbacks.
257 .Bd -literal -offset indent -compact
258 nfsuserd_enable="YES"
265 Without a functioning callback path, a server will never issue Delegations
268 By default, the callback address will be set to the IP address acquired via
269 rtalloc() in the kernel and port# 7745.
270 To override the default port#, a command line option for
274 To get callbacks to work when behind a NAT gateway, a port for the callback
275 service will need to be set up on the NAT gateway and then the address
276 of the NAT gateway (host IP plus port#) will need to be set by assigning the
278 variable vfs.nfs.callback_addr to a string of the form:
282 where the first 4 Ns are the host IP address and the last two are the
283 port# in network byte order (all decimal #s in the range 0-255).
285 To build a kernel with the client that supports
287 linked into it, the option
289 .Bd -literal -offset indent -compact
293 must be specified in the kernel's
297 Options can be specified for the
301 daemons at boot time via the ``nfsuserd_flags'' and ``nfscbd_flags''
305 NFSv4 mount(s) against exported volume(s) on the same host are not recommended,
306 since this can result in a hung NFS server.
307 It occurs when an nfsd thread tries to do an NFSv4 VOP_RECLAIM()/Close RPC
308 as part of acquiring a new vnode.
309 If all other nfsd threads are blocked waiting for lock(s) held by this nfsd
310 thread, then there isn't an nfsd thread to service the Close RPC.
312 .Bl -tag -width /var/db/nfs-stablerestart.bak -compact
313 .It Pa /var/db/nfs-stablerestart
314 NFS V4 stable restart file
315 .It Pa /var/db/nfs-stablerestart.bak
316 backup copy of the file
319 .Xr stablerestart 5 ,
327 At this time, there is no recall of delegations for local file system
329 As such, delegations should only be enabled for file systems
330 that are being used solely as NFS export volumes and are not being accessed
331 via local system calls nor services such as Samba.