1RPC.STATD(8) System Manager's Manual RPC.STATD(8)
2
6 rpc.statd - NSM service daemon
7
9 rpc.statd [-dh?FLNvV] [-H prog] [-n my-name] [-o outgoing-port]
10 [-p listener-port] [-P path]
11 [--nlm-port port] [--nlm-udp-port port]
12
14 File locks are not part of persistent file system state. Lock state is
15 thus lost when a host reboots.
16 Network file systems must also detect when lock state is lost because a
18 remote host has rebooted. After an NFS client reboots, an NFS server
19 must release all file locks held by applications that were running on
20 that client. After a server reboots, a client must remind the server
21 of file locks held by applications running on that client.
22 For NFS version 2 [RFC1094] and NFS version 3 [RFC1813], the Network
24 Status Monitor protocol (or NSM for short) is used to notify NFS peers
25 of reboots. On Linux, two separate user-space components constitute
26 the NSM service:
27 rpc.statd
29 A daemon that listens for reboot notifications from other hosts,
30 and manages the list of hosts to be notified when the local sys‐
31 tem reboots
32 sm-notify
34 A helper program that notifies NFS peers after the local system
35 reboots
36 The local NFS lock manager alerts its local rpc.statd of each remote
38 peer that should be monitored. When the local system reboots, the sm-
39 notify command notifies the NSM service on monitored peers of the
40 reboot. When a remote reboots, that peer notifies the local rpc.statd,
41 which in turn passes the reboot notification back to the local NFS lock
42 manager.
43
45 The first file locking interaction between an NFS client and server
46 causes the NFS lock managers on both peers to contact their local NSM
47 service to store information about the opposite peer. On Linux, the
48 local lock manager contacts rpc.statd.
49 rpc.statd records information about each monitored NFS peer on persis‐
51 tent storage. This information describes how to contact a remote peer
52 in case the local system reboots, how to recognize which monitored peer
53 is reporting a reboot, and how to notify the local lock manager when a
54 monitored peer indicates it has rebooted.
55 An NFS client sends a hostname, known as the client's caller_name, in
57 each file lock request. An NFS server can use this hostname to send
58 asynchronous GRANT calls to a client, or to notify the client it has
59 rebooted.
60 The Linux NFS server can provide the client's caller_name or the
62 client's network address to rpc.statd. For the purposes of the NSM
63 protocol, this name or address is known as the monitored peer's
64 mon_name. In addition, the local lock manager tells rpc.statd what it
65 thinks its own hostname is. For the purposes of the NSM protocol, this
66 hostname is known as my_name.
67 There is no equivalent interaction between an NFS server and a client
69 to inform the client of the server's caller_name. Therefore NFS
70 clients do not actually know what mon_name an NFS server might use in
71 an SM_NOTIFY request. The Linux NFS client uses the server hostname
72 from the mount command to identify rebooting NFS servers.
73 Reboot notification
75 When the local system reboots, the sm-notify command reads the list of
76 monitored peers from persistent storage and sends an SM_NOTIFY request
77 to the NSM service on each listed remote peer. It uses the mon_name
78 string as the destination. To identify which host has rebooted, the
79 sm-notify command sends the my_name string recorded when that remote
80 was monitored. The remote rpc.statd matches incoming SM_NOTIFY
81 requests using this string, or the caller's network address, to one or
82 more peers on its own monitor list.
83 If rpc.statd does not find a peer on its monitor list that matches an
85 incoming SM_NOTIFY request, the notification is not forwarded to the
86 local lock manager. In addition, each peer has its own NSM state num‐
87 ber, a 32-bit integer that is bumped after each reboot by the sm-notify
88 command. rpc.statd uses this number to distinguish between actual
89 reboots and replayed notifications.
90 Part of NFS lock recovery is rediscovering which peers need to be moni‐
92 tored again. The sm-notify command clears the monitor list on persis‐
93 tent storage after each reboot.
94
96 -d, --no-syslog
97 Causes rpc.statd to write log messages on stderr instead of to
98 the system log, if the -F option was also specified.
99 -F, --foreground
101 Keeps rpc.statd attached to its controlling terminal so that NSM
102 operation can be monitored directly or run under a debugger. If
103 this option is not specified, rpc.statd backgrounds itself soon
104 after it starts.
105 -h, -?, --help
107 Causes rpc.statd to display usage information on stderr and then
108 exit.
109 -H, --ha-callout prog
111 Specifies a high availability callout program. If this option
112 is not specified, no callouts are performed. See the High-
113 availability callouts section below for details.
114 -L, --no-notify
116 Prevents rpc.statd from running the sm-notify command when it
117 starts up, preserving the existing NSM state number and monitor
118 list.
119 Note: the sm-notify command contains a check to ensure it runs
121 only once after each system reboot. This prevents spurious
122 reboot notification if rpc.statd restarts without the -L option.
123 -n, --name ipaddr | hostname
125 This string is only used by the sm-notify command as the source
126 address from which to send reboot notification requests.
127 The ipaddr form can be expressed as either an IPv4 or an IPv6
129 presentation address. If this option is not specified,
130 rpc.statd uses a wildcard address as the transport bind address.
131 See sm-notify(8) for details.
132 -N Causes rpc.statd to run the sm-notify command, and then exit.
134 Since the sm-notify command can also be run directly, this
135 option is deprecated.
136 -o, --outgoing-port port
138 Specifies the source port number the sm-notify command should
139 use when sending reboot notifications. See sm-notify(8) for
140 details.
141 -p, --port port
143 Specifies the port number used for RPC listener sockets. If
144 this option is not specified, rpc.statd will try to consult
145 /etc/services, if gets port succeed, set the same port for all
146 listener socket, otherwise chooses a random ephemeral port for
147 each listener socket.
148 This option can be used to fix the port value of its listeners
150 when SM_NOTIFY requests must traverse a firewall between clients
151 and servers.
152 -T, --nlm-port port
154 Specifies the port number that lockd should listen on for NLM
155 requests. This sets both the TCP and UDP ports unless the UDP
156 port is set separately.
157 -U, --nlm-udp-port port
159 Specifies the UDP port number that lockd should listen on for
160 NLM requests.
161 -P, --state-directory-path pathname
163 Specifies the pathname of the parent directory where NSM state
164 information resides. If this option is not specified, rpc.statd
165 uses /var/lib/nfs/statd by default.
166 After starting, rpc.statd attempts to set its effective UID and
168 GID to the owner and group of the subdirectory sm of this direc‐
169 tory. After changing the effective ids, rpc.statd only needs to
170 access files in sm and sm.bak within the state-directory-path.
171 -v, -V, --version
173 Causes rpc.statd to display version information on stderr and
174 then exit.
175
177 Many of the options that can be set on the command line can also be
178 controlled through values set in the [statd] or, in some cases, the
179 [lockd] sections of the /etc/nfs.conf configuration file. Values rec‐
180 ognized in the [statd] section include port, outgoing-port, name,
181 state-directory-path, and ha-callout which each have the same effect as
182 the option with the same name.
183 The values recognized in the [lockd] section include port and udp-port
185 which have the same effect as the --nlm-port and --nlm-udp-port
186 options, respectively.
187
190 The rpc.statd daemon must be started as root to acquire privileges
191 needed to create sockets with privileged source ports, and to access
192 the state information database. Because rpc.statd maintains a long-
193 running network service, however, it drops root privileges as soon as
194 it starts up to reduce the risk of a privilege escalation attack.
195 During normal operation, the effective user ID it chooses is the owner
197 of the state directory. This allows it to continue to access files in
198 that directory after it has dropped its root privileges. To control
199 which user ID rpc.statd chooses, simply use chown(1) to set the owner
200 of the state directory.
201
203 Lock recovery after a reboot is critical to maintaining data integrity
204 and preventing unnecessary application hangs. To help rpc.statd match
205 SM_NOTIFY requests to NLM requests, a number of best practices should
206 be observed, including:
207 The UTS nodename of your systems should match the DNS names that
209 NFS peers use to contact them
210 The UTS nodenames of your systems should always be fully quali‐
212 fied domain names
213 The forward and reverse DNS mapping of the UTS nodenames should
215 be consistent
216 The hostname the client uses to mount the server should match
218 the server's mon_name in SM_NOTIFY requests it sends
219 Unmounting an NFS file system does not necessarily stop either the NFS
221 client or server from monitoring each other. Both may continue moni‐
222 toring each other for a time in case subsequent NFS traffic between the
223 two results in fresh mounts and additional file locking.
224 On Linux, if the lockd kernel module is unloaded during normal opera‐
226 tion, all remote NFS peers are unmonitored. This can happen on an NFS
227 client, for example, if an automounter removes all NFS mount points due
228 to inactivity.
229 High-availability callouts
231 rpc.statd can exec a special callout program during processing of suc‐
232 cessful SM_MON, SM_UNMON, and SM_UNMON_ALL requests, or when it
233 receives SM_NOTIFY. Such a program may be used in High Availability
234 NFS (HA-NFS) environments to track lock state that may need to be
235 migrated after a system reboot.
236 The name of the callout program is specified with the -H option. The
238 program is run with 3 arguments: The first is either add-client del-
239 client or sm-notify depending on the reason for the callout. The sec‐
240 ond is the mon_name of the monitored peer. The third is the call‐
241 er_name of the requesting lock manager for add-client or del-client ,
242 otherwise it is IP_address of the caller sending SM_NOTIFY. The forth
243 is the state_value in the SM_NOTIFY request.
244 IPv6 and TI-RPC support
247 TI-RPC is a pre-requisite for supporting NFS on IPv6. If TI-RPC sup‐
248 port is built into rpc.statd, it attempts to start listeners on network
249 transports marked 'visible' in /etc/netconfig. As long as at least one
250 network transport listener starts successfully, rpc.statd will operate.
251
253 RPC_STATD_NO_NOTIFY=
254 If set to a positive integer, has the same effect as
255 --no-notify.
256
258 /var/lib/nfs/statd/sm directory containing monitor list
259 /var/lib/nfs/statd/sm.bak
261 directory containing notify list
262 /var/lib/nfs/statd/state NSM state number for this host
264 /var/run/run.statd.pid pid file
266 /etc/netconfig network transport capability database
268
270 sm-notify(8), nfs(5), rpc.nfsd(8), rpcbind(8), tcpd(8), iptables(8),
271 netconfig(5)
272 RFC 1094 - "NFS: Network File System Protocol Specification"
274 RFC 1813 - "NFS Version 3 Protocol Specification"
275 OpenGroup Protocols for Interworking: XNFS, Version 3W - Chapter 11
276
278 Jeff Uphoff <juphoff@users.sourceforge.net>
279 Olaf Kirch <okir@monad.swb.de>
280 H.J. Lu <hjl@gnu.org>
281 Lon Hohberger <hohberger@missioncriticallinux.com>
282 Paul Clements <paul.clements@steeleye.com>
283 Chuck Lever <chuck.lever@oracle.com>
284 1 November 2009 RPC.STATD(8)