# statd

## 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 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 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 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
           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.
    


## 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_
                  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-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-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



           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.
    


## 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
                  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



           **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
    


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