rpc.statd(8) - man - phpMan

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



NAME
       rpc.statd - NSM service daemon

SYNOPSIS
       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
       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  re‐
       booted.   After  an NFS client reboots, an NFS server must release all file locks held by ap‐
       plications 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 mon‐
       itored.   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.

NSM OPERATION IN DETAIL
       The  first file locking interaction between an NFS client and server causes the NFS lock man‐
       agers on both peers to contact their local NSM service to store information about  the  oppo‐
       site peer.  On Linux, the local lock manager contacts rpc.statd.

       rpc.statd  records information about each monitored NFS peer on persistent storage.  This in‐
       formation 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 man‐
       ager 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 no‐
       tify 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 moni‐
       tored 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 net‐
       work 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  re‐
       quest,  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-no‐‐
       tify  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
       -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 mon‐
              itored  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 with‐
              out the -L option.

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

              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 details.

       -p, --port port
              Specifies the port number used for RPC listener sockets.  If this option is not speci‐
              fied, 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 lis‐
              tener 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-directory-path.

       -v, -V, --version
              Causes rpc.statd to display version information on stderr and then exit.

CONFIGURATION FILE
       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-di‐‐
       rectory-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
       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 direc‐
       tory.  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.

ADDITIONAL NOTES
       Lock  recovery after a reboot is critical to maintaining data integrity and preventing unnec‐
       essary application hangs.  To help rpc.statd match SM_NOTIFY requests to NLM requests, a num‐
       ber of best practices should be observed, including:

              The UTS nodename of your systems should match the DNS names that NFS peers use to con‐
              tact 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  re‐
       moves 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_UN‐
       MON, 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/net‐
       config.  As long as at least one network transport listener  starts  successfully,  rpc.statd
       will operate.

ENVIRONMENT
       RPC_STATD_NO_NOTIFY=
              If set to a positive integer, has the same effect as --no-notify.

FILES
       /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

       /run/run.statd.pid       pid file

       /etc/netconfig           network transport capability database

SEE ALSO
       sm-notify(8), nfs(5), rpc.nfsd(8), rpcbind(8), tcpd(8), hosts_access(5), iptables(8), netcon‐‐
       fig(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
       Jeff Uphoff <juphoff AT users.net>
       Olaf Kirch <okir AT monad.de>
       H.J. Lu <hjl AT gnu.org>
       Lon Hohberger <hohberger AT missioncriticallinux.com>
       Paul Clements <paul.clements AT steeleye.com>
       Chuck Lever <chuck.lever AT oracle.com>



                                           1 November 2009                              RPC.STATD(8)