3 .\" Copyright (C) 1999 Olaf Kirch <okir@monad.swb.de>
4 .\" Modified by Jeffrey A. Uphoff, 1999, 2002, 2005.
5 .\" Modified by Lon Hohberger, 2000.
6 .\" Modified by Paul Clements, 2004.
8 .\" Rewritten by Chuck Lever <chuck.lever@oracle.com>, 2009.
9 .\" Copyright 2009 Oracle. All rights reserved.
11 .TH RPC.STATD 8 "1 November 2009
13 rpc.statd \- NSM service daemon
15 .BI "rpc.statd [-dh?FLNvVw] [-H " prog "] [-n " my-name "] [-o " outgoing-port "] [-p " listener-port "] [-P " path " ]
17 File locks are not part of persistent file system state.
18 Lock state is thus lost when a host reboots.
20 Network file systems must also detect when lock state is lost
21 because a remote host has rebooted.
22 After an NFS client reboots, an NFS server must release all file locks
23 held by applications that were running on that client.
24 After a server reboots, a client must remind the
25 server of file locks held by applications running on that client.
27 For NFS version 2 [RFC1094] and NFS version 3 [RFC1813], the
28 .I Network Status Monitor
29 protocol (or NSM for short)
30 is used to notify NFS peers of reboots.
31 On Linux, two separate user-space components constitute the NSM service:
34 A daemon that listens for reboot notifications from other hosts, and
35 manages the list of hosts to be notified when the local system reboots
38 A helper program that notifies NFS peers after the local system reboots
40 The local NFS lock manager alerts its local
42 of each remote peer that should be monitored.
43 When the local system reboots, the
45 command notifies the NSM service on monitored peers of the reboot.
46 When a remote reboots, that peer notifies the local
48 which in turn passes the reboot notification
49 back to the local NFS lock manager.
50 .SH NSM OPERATION IN DETAIL
51 The first file locking interaction between an NFS client and server causes
52 the NFS lock managers on both peers to contact their local NSM service to
53 store information about the opposite peer.
54 On Linux, the local lock manager contacts
58 records information about each monitored NFS peer on persistent storage.
59 This information describes how to contact a remote peer
60 in case the local system reboots,
61 how to recognize which monitored peer is reporting a reboot,
62 and how to notify the local lock manager when a monitored peer
63 indicates it has rebooted.
65 An NFS client sends a hostname, known as the client's
67 in each file lock request.
68 An NFS server can use this hostname to send asynchronous GRANT
69 calls to a client, or to notify the client it has rebooted.
71 The Linux NFS server can provide the client's
73 or the client's network address to
75 For the purposes of the NSM protocol,
76 this name or address is known as the monitored peer's
78 In addition, the local lock manager tells
80 what it thinks its own hostname is.
81 For the purposes of the NSM protocol,
82 this hostname is known as
85 There is no equivalent interaction between an NFS server and a client
86 to inform the client of the server's
88 Therefore NFS clients do not actually know what
90 an NFS server might use in an SM_NOTIFY request.
91 The Linux NFS client uses the server hostname from the mount command
92 to identify rebooting NFS servers.
93 .SS Reboot notification
94 When the local system reboots, the
96 command reads the list of monitored peers from persistent storage and
97 sends an SM_NOTIFY request to the NSM service on each listed remote peer.
100 string as the destination.
101 To identify which host has rebooted, the
103 command normally sends the results of
110 matches incoming SM_NOTIFY requests using this string,
111 or the caller's network address,
112 to one or more peers on its own monitor list.
116 does not find a peer on its monitor list that matches
117 an incoming SM_NOTIFY request,
118 the notification is not forwarded to the local lock manager.
119 In addition, each peer has its own
120 .IR "NSM state number" ,
121 a 32-bit integer that is bumped after each reboot by the
125 uses this number to distinguish between actual reboots
126 and replayed notifications.
128 Part of NFS lock recovery is rediscovering
129 which peers need to be monitored again.
132 command clears the monitor list on persistent storage after each reboot.
135 .BR -d , " --no-syslog
138 to write log messages on
140 instead of to the system log,
143 option was also specified.
145 .BR -F , " --foreground
148 attached to its controlling terminal so that NSM
149 operation can be monitored directly or run under a debugger.
150 If this option is not specified,
152 backgrounds itself soon after it starts.
154 .BR -h , " -?" , " --help
157 to display usage information on
161 .BI "\-H," "" " \-\-ha-callout " prog
162 Specifies a high availability callout program.
163 If this option is not specified, no callouts are performed.
165 .B High-availability callouts
166 section below for details.
168 .BR -L , " --no-notify
173 command when it starts up,
174 preserving the existing NSM state number and monitor list.
178 command contains a check to ensure it runs only once after each system reboot.
179 This prevents spurious reboot notification if
185 .BI "\-n, " "" "\-\-name " ipaddr " | " hostname
186 Specifies the bind address used for RPC listener sockets.
189 form can be expressed as either an IPv4 or an IPv6 presentation address.
190 If this option is not specified,
192 uses a wildcard address as the transport bind address.
194 This string is also passed to the
196 command to be used as the source address from which
197 to send reboot notification requests.
207 command, and then exit.
210 command can also be run directly, this option is deprecated.
212 .BI "\-o," "" " \-\-outgoing\-port " port
213 Specifies the source port number the
215 command should use when sending reboot notifications.
220 .BI "\-p," "" " \-\-port " port
221 Specifies the port number used for RPC listener sockets.
222 If this option is not specified,
224 chooses a random ephemeral port for each listener socket.
226 This option can be used to fix the port value of its listeners when
227 SM_NOTIFY requests must traverse a firewall between clients and servers.
229 .BI "\-P, " "" \-\-state\-directory\-path " pathname
230 Specifies the pathname of the parent directory
231 where NSM state information resides.
232 If this option is not specified,
240 attempts to set its effective UID and GID to the owner
241 and group of this directory.
243 .BR -v ", " -V ", " --version
246 to display version information on
252 daemon must be started as root to acquire privileges needed
253 to create sockets with privileged source ports, and to access the
254 state information database.
257 maintains a long-running network service, however, it drops root privileges
258 as soon as it starts up to reduce the risk of a privilege escalation attack.
260 During normal operation,
261 the effective user ID it chooses is the owner of the state directory.
262 This allows it to continue to access files in that directory after it
263 has dropped its root privileges.
264 To control which user ID
271 You can also protect your
279 library, add the hostnames of peers that should be allowed access to
280 .IR /etc/hosts.allow .
285 binary has a different filename.
287 For further information see the
293 Lock recovery after a reboot is critical to maintaining data integrity
294 and preventing unnecessary application hangs.
298 match SM_NOTIFY requests to NLM requests, a number of best practices
299 should be observed, including:
301 The UTS nodename of your systems should match the DNS names that NFS
302 peers use to contact them
304 The UTS nodenames of your systems should always be fully qualified domain names
306 The forward and reverse DNS mapping of the UTS nodenames should be
309 The hostname the client uses to mount the server should match the server's
311 in SM_NOTIFY requests it sends
313 The use of network addresses as a
317 string should be avoided when
318 interoperating with non-Linux NFS implementations.
320 Unmounting an NFS file system does not necessarily stop
321 either the NFS client or server from monitoring each other.
322 Both may continue monitoring each other for a time in case subsequent
323 NFS traffic between the two results in fresh mounts and additional
328 kernel module is unloaded during normal operation,
329 all remote NFS peers are unmonitored.
330 This can happen on an NFS client, for example,
331 if an automounter removes all NFS mount
332 points due to inactivity.
333 .SS High-availability callouts
335 can exec a special callout program during processing of
336 successful SM_MON, SM_UNMON, and SM_UNMON_ALL requests.
337 Such a program may be used in High Availability NFS (HA-NFS)
338 environments to track lock state that may need to be migrated after
341 The name of the callout program is specified with the
344 The program is run with 3 arguments:
349 depending on the reason for the callout.
352 of the monitored peer.
355 of the requesting lock manager.
356 .SS IPv6 and TI-RPC support
357 TI-RPC is a pre-requisite for supporting NFS on IPv6.
358 If TI-RPC support is built into
360 it attempts to start listeners on network transports marked
363 As long as at least one network transport listener starts successfully,
369 directory containing monitor list
371 .I /var/lib/nfs/sm.bak
372 directory containing notify list
374 .I /var/lib/nfs/state
375 NSM state number for this host
377 .I /var/run/run.statd.pid
381 network transport capability database
388 .BR hosts_access (5),
392 RFC 1094 - "NFS: Network File System Protocol Specification"
394 RFC 1813 - "NFS Version 3 Protocol Specification"
396 OpenGroup Protocols for Interworking: XNFS, Version 3W - Chapter 11
398 Jeff Uphoff <juphoff@users.sourceforge.net>
400 Olaf Kirch <okir@monad.swb.de>
402 H.J. Lu <hjl@gnu.org>
404 Lon Hohberger <hohberger@missioncriticallinux.com>
406 Paul Clements <paul.clements@steeleye.com>
408 Chuck Lever <chuck.lever@oracle.com>