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RPC.STATD(8)							  RPC.STATD(8)

NAME
       rpc.statd - NSM service daemon

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

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 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 sys‐
	      tem 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.

NSM OPERATION IN DETAIL
       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 persis‐
       tent 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  normally sends the results of gethostname(3) as the
       my_name	string.	  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  num‐
       ber, 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 moni‐
       tored again.  The sm-notify command clears the monitor list on  persis‐
       tent 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 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 pre‐
	      sentation 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  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.

       -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.

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 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	 host‐
       names  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 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	quali‐
	      fied 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

	      The  use	of network addresses as a mon_name or a my_name string
	      should be avoided when interoperating with non-Linux NFS	imple‐
	      mentations.

       Unmounting  an NFS file system does not necessarily stop either the NFS
       client or server from monitoring each other.  Both may  continue	 moni‐
       toring 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	opera‐
       tion,  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 suc‐
       cessful SM_MON, SM_UNMON, and SM_UNMON_ALL requests.   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 or del-
       client 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.

   IPv6 and TI-RPC support
       TI-RPC is a pre-requisite for supporting NFS on IPv6.  If  TI-RPC  sup‐
       port is built into rpc.statd, it attempts to start listeners on network
       transports marked /etc/netconfig.  As long  as  at  least  one  network
       transport listener starts successfully, rpc.statd will operate.

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

       /var/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), 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
       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>

				1 November 2009			  RPC.STATD(8)
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