rpc.statd(8) — Linux manual page


RPC.STATD(8)               System Manager's Manual              RPC.STATD(8)

NAME         top

       rpc.statd - NSM service daemon

SYNOPSIS         top

       rpc.statd [-dh?FLNvV] [-H prog] [-n my-name] [-o outgoing-port]
                 [-p listener-port] [-P path]
                 [--nlm-port port] [--nlm-udp-port port]

DESCRIPTION         top

       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:

              A daemon that listens for reboot notifications from other
              hosts, and manages the list of hosts to be notified when the
              local system reboots

              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

       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.

OPTIONS         top

       -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

       -n, --name ipaddr | hostname
              This string is only used by the sm-notify command as the
              source address from which to send reboot notification

              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.  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

       -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 the subdirectory sm of this
              directory.  After changing the effective ids, rpc.statd only
              needs to access files in sm and sm.bak within the state-

       -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.

SECURITY         top

       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


       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.

ENVIRONMENT         top

              If set to a positive integer, has the same effect as

FILES         top

       /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

SEE ALSO         top

       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

AUTHORS         top

       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>

COLOPHON         top

       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
       2020-08-13.  (At that time, the date of the most recent commit that
       was found in the repository was 2020-08-07.)  If you discover any
       rendering problems in this HTML version 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 manual page), send a mail to

                               1 November 2009                  RPC.STATD(8)

Pages that refer to this page: nfs(5)nfs.conf(5)sm-notify(8)