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diff --git a/upstream/debian-bookworm/man8/sm-notify.8 b/upstream/debian-bookworm/man8/sm-notify.8 new file mode 100644 index 00000000..addf5d3c --- /dev/null +++ b/upstream/debian-bookworm/man8/sm-notify.8 @@ -0,0 +1,366 @@ +.\"@(#)sm-notify.8" +.\" +.\" Copyright (C) 2004 Olaf Kirch <okir@suse.de> +.\" +.\" Rewritten by Chuck Lever <chuck.lever@oracle.com>, 2009. +.\" Copyright 2009 Oracle. All rights reserved. +.\" +.TH SM-NOTIFY 8 "1 November 2009 +.SH NAME +sm-notify \- send reboot notifications to NFS peers +.SH SYNOPSIS +.BI "/usr/sbin/sm-notify [-dfn] [-m " minutes "] [-v " name "] [-p " notify-port "] [-P " path "] +.SH DESCRIPTION +File locks are not part of persistent file system state. +Lock state is thus lost when a host reboots. +.PP +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. +.PP +For NFS version 2 and version 3, the +.I 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: +.TP +.B sm-notify +A helper program that notifies NFS peers after the local system reboots +.TP +.B 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 +.PP +The local NFS lock manager alerts its local +.B rpc.statd +of each remote peer that should be monitored. +When the local system reboots, the +.B sm-notify +command notifies the NSM service on monitored peers of the reboot. +When a remote reboots, that peer notifies the local +.BR rpc.statd , +which in turn passes the reboot notification +back to the local NFS lock manager. +.SH 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 +.BR rpc.statd . +.PP +.B 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. +.PP +An NFS client sends a hostname, known as the client's +.IR 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. +.PP +The Linux NFS server can provide the client's +.I caller_name +or the client's network address to +.BR rpc.statd . +For the purposes of the NSM protocol, +this name or address is known as the monitored peer's +.IR mon_name . +In addition, the local lock manager tells +.B rpc.statd +what it thinks its own hostname is. +For the purposes of the NSM protocol, +this hostname is known as +.IR my_name . +.PP +There is no equivalent interaction between an NFS server and a client +to inform the client of the server's +.IR caller_name . +Therefore NFS clients do not actually know what +.I mon_name +an NFS server might use in an SM_NOTIFY request. +The Linux NFS client records the server's hostname used on the mount command +to identify rebooting NFS servers. +.SS Reboot notification +When the local system reboots, the +.B 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 +.I mon_name +string as the destination. +To identify which host has rebooted, the +.B sm-notify +command normally sends +.I my_name +string recorded when that remote was monitored. +The remote +.B 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. +.PP +If +.B 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 +.IR "NSM state number" , +a 32-bit integer that is bumped after each reboot by the +.B sm-notify +command. +.B rpc.statd +uses this number to distinguish between actual reboots +and replayed notifications. +.PP +Part of NFS lock recovery is rediscovering +which peers need to be monitored again. +The +.B sm-notify +command clears the monitor list on persistent storage after each reboot. +.SH OPTIONS +.TP +.B -d +Keeps +.B sm-notify +attached to its controlling terminal and running in the foreground +so that notification progress may be monitored directly. +.TP +.B -f +Send notifications even if +.B sm-notify +has already run since the last system reboot. +.TP +.BI -m " retry-time +Specifies the length of time, in minutes, to continue retrying +notifications to unresponsive hosts. +If this option is not specified, +.B sm-notify +attempts to send notifications for 15 minutes. +Specifying a value of 0 causes +.B sm-notify +to continue sending notifications to unresponsive peers +until it is manually killed. +.IP +Notifications are retried if sending fails, +the remote does not respond, +the remote's NSM service is not registered, +or if there is a DNS failure +which prevents the remote's +.I mon_name +from being resolved to an address. +.IP +Hosts are not removed from the notification list until a valid +reply has been received. +However, the SM_NOTIFY procedure has a void result. +There is no way for +.B sm-notify +to tell if the remote recognized the sender and has started +appropriate lock recovery. +.TP +.B -n +Prevents +.B sm-notify +from updating the local system's NSM state number. +.TP +.BI -p " port +Specifies the source port number +.B sm-notify +should use when sending reboot notifications. +If this option is not specified, a randomly chosen ephemeral port is used. +.IP +This option can be used to traverse a firewall between client and server. +.TP +.BI "\-P, " "" \-\-state\-directory\-path " pathname +Specifies the pathname of the parent directory +where NSM state information resides. +If this option is not specified, +.B sm-notify +uses +.I /var/lib/nfs +by default. +.IP +After starting, +.B sm-notify +attempts to set its effective UID and GID to the owner +and group of the subdirectory +.B sm +of this directory. After changing the effective ids, +.B sm-notify +only needs to access files in +.B sm +and +.B sm.bak +within the state-directory-path. +.TP +.BI -v " ipaddr " | " hostname +Specifies the network address from which to send reboot notifications, +and the +.I mon_name +argument to use when sending SM_NOTIFY requests. +If this option is not specified, +.B sm-notify +uses a wildcard address as the transport bind address, +and uses the +.I my_name +recorded when the remote was monitored as the +.I mon_name +argument when sending SM_NOTIFY requests. +.IP +The +.I ipaddr +form can be expressed as either an IPv4 or an IPv6 presentation address. +If the +.I ipaddr +form is used, the +.B sm-notify +command converts this address to a hostname for use as the +.I mon_name +argument when sending SM_NOTIFY requests. +.IP +This option can be useful in multi-homed configurations where +the remote requires notification from a specific network address. +.SH CONFIGURATION FILE +Many of the options that can be set on the command line can also be +controlled through values set in the +.B [sm-notify] +or, in one case, the +.B [statd] +section of the +.I /etc/nfs.conf +configuration file. + +Values recognized in the +.B [sm-notify] +section include: +.BR retry-time , +.BR outgoing-port ", and" +.BR outgoing-addr . +These have the same effect as the command line options +.BR m , +.BR p ", and" +.B v +respectively. + +An additional value recognized in the +.B [sm-notify] +section is +.BR lift-grace . +By default, +.B sm-notify +will lift lockd's grace period early if it has no hosts to notify. +Some high availability configurations will run one +.B sm-notify +per floating IP address. In these configurations, lifting the +grace period early may prevent clients from reclaiming locks. +.RB "Setting " lift-grace " to " n +will prevent +.B sm-notify +from ending the grace period early. +.B lift-grace +has no corresponding command line option. + +The value recognized in the +.B [statd] +section is +.BR state-directory-path . + +.SH SECURITY +The +.B sm-notify +command must be started as root to acquire privileges needed +to access the state information database. +It drops root privileges +as soon as it starts up to reduce the risk of a privilege escalation attack. +.PP +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 +.B rpc.statd +chooses, simply use +.BR chown (1) +to set the owner of +the state directory. +.SH ADDITIONAL NOTES +Lock recovery after a reboot is critical to maintaining data integrity +and preventing unnecessary application hangs. +.PP +To help +.B rpc.statd +match SM_NOTIFY requests to NLM requests, a number of best practices +should be observed, including: +.IP +The UTS nodename of your systems should match the DNS names that NFS +peers use to contact them +.IP +The UTS nodenames of your systems should always be fully qualified domain names +.IP +The forward and reverse DNS mapping of the UTS nodenames should be +consistent +.IP +The hostname the client uses to mount the server should match the server's +.I mon_name +in SM_NOTIFY requests it sends +.PP +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. +.PP +On Linux, if the +.B 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. +.SS IPv6 and TI-RPC support +TI-RPC is a pre-requisite for supporting NFS on IPv6. +If TI-RPC support is built into the +.B sm-notify +command ,it will choose an appropriate IPv4 or IPv6 transport +based on the network address returned by DNS for each remote peer. +It should be fully compatible with remote systems +that do not support TI-RPC or IPv6. +.PP +Currently, the +.B sm-notify +command supports sending notification only via datagram transport protocols. +.SH FILES +.TP 2.5i +.I /var/lib/nfs/sm +directory containing monitor list +.TP 2.5i +.I /var/lib/nfs/sm.bak +directory containing notify list +.TP 2.5i +.I /var/lib/nfs/state +NSM state number for this host +.TP 2.5i +.I /proc/sys/fs/nfs/nsm_local_state +kernel's copy of the NSM state number +.SH SEE ALSO +.BR rpc.statd (8), +.BR nfs (5), +.BR uname (2), +.BR hostname (7) +.PP +RFC 1094 - "NFS: Network File System Protocol Specification" +.br +RFC 1813 - "NFS Version 3 Protocol Specification" +.br +OpenGroup Protocols for Interworking: XNFS, Version 3W - Chapter 11 +.SH AUTHORS +Olaf Kirch <okir@suse.de> +.br +Chuck Lever <chuck.lever@oracle.com> |