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    Command:

    rpc.statd

    
    
    

    SYNOPSIS

           rpc.statd  [-dh?FLNvV]  [-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.
    
           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  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-
                  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.
    
           -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:
    
           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 'visible' in /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>
    
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