Provided by: nfs-common_2.6.2-4ubuntu1_amd64 bug


       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:

              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


       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

       -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
              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
              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.


       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

       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.


              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

       /run/       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),

       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 <>
       Olaf Kirch <>
       H.J. Lu <>
       Lon Hohberger <>
       Paul Clements <>
       Chuck Lever <>

                                         1 November 2009                             RPC.STATD(8)