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NAME | SYNOPSIS | DESCRIPTION | NSM OPERATION IN DETAIL | OPTIONS | CONFIGURATION FILE | SECURITY | ADDITIONAL NOTES | ENVIRONMENT | FILES | SEE ALSO | AUTHORS | COLOPHON |
RPC.STATD(8) System Manager's Manual RPC.STATD(8)
rpc.statd - NSM service daemon
rpc.statd [-dh?FLNvV] [-H prog] [-n my-name] [-o outgoing-port]
[-p listener-port] [-P path]
[--nlm-port port] [--nlm-udp-port port]
File locks are not part of persistent file system state. Lock state
is thus lost when a host reboots.
Network file systems must also detect when lock state is lost because
a remote host has rebooted. After an NFS client reboots, an NFS
server must release all file locks held by applications that were
running on that client. After a server reboots, a client must remind
the server of file locks held by applications running on that client.
For NFS version 2 [RFC1094] and NFS version 3 [RFC1813], the Network
Status Monitor protocol (or NSM for short) is used to notify NFS
peers of reboots. On Linux, two separate user-space components
constitute the NSM service:
rpc.statd
A daemon that listens for reboot notifications from other
hosts, and manages the list of hosts to be notified when the
local system reboots
sm-notify
A helper program that notifies NFS peers after the local
system reboots
The local NFS lock manager alerts its local rpc.statd of each remote
peer that should be monitored. When the local system reboots, the
sm-notify command notifies the NSM service on monitored peers of the
reboot. When a remote reboots, that peer notifies the local
rpc.statd, which in turn passes the reboot notification back to the
local NFS lock manager.
The first file locking interaction between an NFS client and server
causes the NFS lock managers on both peers to contact their local NSM
service to store information about the opposite peer. On Linux, the
local lock manager contacts rpc.statd.
rpc.statd records information about each monitored NFS peer on
persistent storage. This information describes how to contact a
remote peer in case the local system reboots, how to recognize which
monitored peer is reporting a reboot, and how to notify the local
lock manager when a monitored peer indicates it has rebooted.
An NFS client sends a hostname, known as the client's caller_name, in
each file lock request. An NFS server can use this hostname to send
asynchronous GRANT calls to a client, or to notify the client it has
rebooted.
The Linux NFS server can provide the client's caller_name or the
client's network address to rpc.statd. For the purposes of the NSM
protocol, this name or address is known as the monitored peer's
mon_name. In addition, the local lock manager tells rpc.statd what
it thinks its own hostname is. For the purposes of the NSM protocol,
this hostname is known as my_name.
There is no equivalent interaction between an NFS server and a client
to inform the client of the server's caller_name. Therefore NFS
clients do not actually know what mon_name an NFS server might use in
an SM_NOTIFY request. The Linux NFS client uses the server hostname
from the mount command to identify rebooting NFS servers.
Reboot notification
When the local system reboots, the sm-notify command reads the list
of monitored peers from persistent storage and sends an SM_NOTIFY
request to the NSM service on each listed remote peer. It uses the
mon_name string as the destination. To identify which host has
rebooted, the sm-notify command sends the my_name string recorded
when that remote was monitored. The remote rpc.statd matches
incoming SM_NOTIFY requests using this string, or the caller's
network address, to one or more peers on its own monitor list.
If rpc.statd does not find a peer on its monitor list that matches an
incoming SM_NOTIFY request, the notification is not forwarded to the
local lock manager. In addition, each peer has its own NSM state
number, a 32-bit integer that is bumped after each reboot by the sm-
notify command. rpc.statd uses this number to distinguish between
actual reboots and replayed notifications.
Part of NFS lock recovery is rediscovering which peers need to be
monitored again. The sm-notify command clears the monitor list on
persistent storage after each reboot.
-d, --no-syslog
Causes rpc.statd to write log messages on stderr instead of to
the system log, if the -F option was also specified.
-F, --foreground
Keeps rpc.statd attached to its controlling terminal so that
NSM operation can be monitored directly or run under a
debugger. If this option is not specified, rpc.statd
backgrounds itself soon after it starts.
-h, -?, --help
Causes rpc.statd to display usage information on stderr and
then exit.
-H, --ha-callout prog
Specifies a high availability callout program. If this option
is not specified, no callouts are performed. See the High-
availability callouts section below for details.
-L, --no-notify
Prevents rpc.statd from running the sm-notify command when it
starts up, preserving the existing NSM state number and
monitor list.
Note: the sm-notify command contains a check to ensure it runs
only once after each system reboot. This prevents spurious
reboot notification if rpc.statd restarts without the -L
option.
-n, --name ipaddr | hostname
Specifies the bind address used for RPC listener sockets. The
ipaddr form can be expressed as either an IPv4 or an IPv6
presentation address. If this option is not specified,
rpc.statd uses a wildcard address as the transport bind
address.
This string is also passed to the sm-notify command to be used
as the source address from which to send reboot notification
requests. See sm-notify(8) for details.
-N Causes rpc.statd to run the sm-notify command, and then exit.
Since the sm-notify command can also be run directly, this
option is deprecated.
-o, --outgoing-port port
Specifies the source port number the sm-notify command should
use when sending reboot notifications. See sm-notify(8) for
details.
-p, --port port
Specifies the port number used for RPC listener sockets. If
this option is not specified, rpc.statd will try to consult
/etc/services, if gets port succeed, set the same port for all
listener socket, otherwise chooses a random ephemeral port for
each listener socket.
This option can be used to fix the port value of its listeners
when SM_NOTIFY requests must traverse a firewall between
clients and servers.
-T, --nlm-port port
Specifies the port number that lockd should listen on for NLM
requests. This sets both the TCP and UDP ports unless the UDP
port is set separately.
-U, --nlm-udp-port port
Specifies the UDP port number that lockd should listen on for
NLM requests.
-P, --state-directory-path pathname
Specifies the pathname of the parent directory where NSM state
information resides. If this option is not specified,
rpc.statd uses /var/lib/nfs by default.
After starting, rpc.statd attempts to set its effective UID
and GID to the owner and group of this directory.
-v, -V, --version
Causes rpc.statd to display version information on stderr and
then exit.
Many of the options that can be set on the command line can also be
controlled through values set in the [statd] or, in some cases, the
[lockd] sections of the /etc/nfs.conf configuration file. Values
recognized in the [statd] section include port, outgoing-port, name,
state-directory-path, and ha-callout which each have the same effect
as the option with the same name.
The values recognized in the [lockd] section include port and udp-
port which have the same effect as the --nlm-port and --nlm-udp-port
options, respectively.
The rpc.statd daemon must be started as root to acquire privileges
needed to create sockets with privileged source ports, and to access
the state information database. Because rpc.statd maintains a long-
running network service, however, it drops root privileges as soon as
it starts up to reduce the risk of a privilege escalation attack.
During normal operation, the effective user ID it chooses is the
owner of the state directory. This allows it to continue to access
files in that directory after it has dropped its root privileges. To
control which user ID rpc.statd chooses, simply use chown(1) to set
the owner of the state directory.
You can also protect your rpc.statd listeners using the tcp_wrapper
library or iptables(8). To use the tcp_wrapper library, add the
hostnames of peers that should be allowed access to /etc/hosts.allow.
Use the daemon name statd even if the rpc.statd binary has a
different filename.
For further information see the tcpd(8) and hosts_access(5) man
pages.
Lock recovery after a reboot is critical to maintaining data
integrity and preventing unnecessary application hangs. To help
rpc.statd match SM_NOTIFY requests to NLM requests, a number of best
practices should be observed, including:
The UTS nodename of your systems should match the DNS names
that NFS peers use to contact them
The UTS nodenames of your systems should always be fully
qualified domain names
The forward and reverse DNS mapping of the UTS nodenames
should be consistent
The hostname the client uses to mount the server should match
the server's mon_name in SM_NOTIFY requests it sends
Unmounting an NFS file system does not necessarily stop either the
NFS client or server from monitoring each other. Both may continue
monitoring each other for a time in case subsequent NFS traffic
between the two results in fresh mounts and additional file locking.
On Linux, if the lockd kernel module is unloaded during normal
operation, all remote NFS peers are unmonitored. This can happen on
an NFS client, for example, if an automounter removes all NFS mount
points due to inactivity.
High-availability callouts
rpc.statd can exec a special callout program during processing of
successful SM_MON, SM_UNMON, and SM_UNMON_ALL requests, or when it
receives SM_NOTIFY. Such a program may be used in High Availability
NFS (HA-NFS) environments to track lock state that may need to be
migrated after a system reboot.
The name of the callout program is specified with the -H option. The
program is run with 3 arguments: The first is either add-client del-
client or sm-notify depending on the reason for the callout. The
second is the mon_name of the monitored peer. The third is the
caller_name of the requesting lock manager for add-client or del-
client , otherwise it is IP_address of the caller sending SM_NOTIFY.
The forth is the state_value in the SM_NOTIFY request.
IPv6 and TI-RPC support
TI-RPC is a pre-requisite for supporting NFS on IPv6. If TI-RPC
support is built into rpc.statd, it attempts to start listeners on
network transports marked 'visible' in /etc/netconfig. As long as at
least one network transport listener starts successfully, rpc.statd
will operate.
RPC_STATD_NO_NOTIFY=
If set to a positive integer, has the same effect as
--no-notify.
/var/lib/nfs/sm directory containing monitor list
/var/lib/nfs/sm.bak directory containing notify list
/var/lib/nfs/state NSM state number for this host
/var/run/run.statd.pid pid file
/etc/netconfig network transport capability database
sm-notify(8), nfs(5), rpc.nfsd(8), rpcbind(8), tcpd(8),
hosts_access(5), iptables(8), netconfig(5)
RFC 1094 - "NFS: Network File System Protocol Specification"
RFC 1813 - "NFS Version 3 Protocol Specification"
OpenGroup Protocols for Interworking: XNFS, Version 3W - Chapter 11
Jeff Uphoff <juphoff@users.sourceforge.net>
Olaf Kirch <okir@monad.swb.de>
H.J. Lu <hjl@gnu.org>
Lon Hohberger <hohberger@missioncriticallinux.com>
Paul Clements <paul.clements@steeleye.com>
Chuck Lever <chuck.lever@oracle.com>
This page is part of the nfs-utils (NFS utilities) project.
Information about the project can be found at
⟨http://linux-nfs.org/wiki/index.php/Main_Page⟩. If you have a bug
report for this manual page, see
⟨http://linux-nfs.org/wiki/index.php/Main_Page⟩. This page was
obtained from the project's upstream Git repository
⟨http://git.linux-nfs.org/?p=steved/nfs-utils.git;a=summary⟩ on
2017-07-05. If you discover any rendering problems in this HTML ver‐
sion of the page, or you believe there is a better or more up-to-date
source for the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original man‐
ual page), send a mail to man-pages@man7.org
1 November 2009 RPC.STATD(8)
Pages that refer to this page: nfs(5), nfs.conf(5), sm-notify(8)