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.\" Copyright (c) 1995 A.R.Gordon, andrew.gordon@net-tel.co.uk
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.Dd September 19, 1995
.Dt RPC.STATD 8
.Os
.Sh NAME
.Nm rpc.statd 
.Nd host status monitoring daemon
.Sh SYNOPSIS
.Nm rpc.statd
.Op Fl d
.Sh DESCRIPTION
.Nm rpc.rstatd
is a daemon which co-operates with rpc.statd daemons on other hosts to provide
a status monitoring service.  The daemon accepts requests from
programs running on the local host (typically,
.Xr rpc.lockd 8 ,
the NFS file locking daemon) to monitor the status of specified
hosts.  If a monitored host crashes and restarts, the remote daemon will
notify the local daemon, which in turn will notify the local program(s)
which requested the monitoring service.  Conversely, if this host crashes
and re-starts, when the
.Nm rpc.statd
re-starts, it will notify all of the hosts which were being monitored
at the time of the crash.
.Pp
Options and operands available for
.Nm rpc.statd :
.Bl -tag -width Ds
.It Fl d
The
.Fl d
option causes debugging information to be written to syslog, recording
all RPC transations to the daemon.  These messages are logged with level
LOG_DEBUG and facility LOG_DAEMON.  Error conditions are logged irrespective
of this option, using level LOG_ERR.
.El
.Pp
The
.Nm rpc.rstatd
daemon must NOT be invoked by
.Xr inetd 8
because the protocol assumes that the daemon will run from system start time.
Instead, it should be run from
.Xr rc 8
after the network has been started.
.Sh FILES
.Bl -tag -width /usr/include/rpcsvc/sm_inter.x -compact
.It Pa /var/db/statd.status
non-volatile record of currently monitored hosts.
.It Pa /usr/include/rpcsvc/sm_inter.x
RPC protocol specification used by local applications to register monitoring requests.
.El
.Sh SEE ALSO
.Xr syslog 3 ,
.Xr rc 8 ,
.Xr rpc.lockd 8
.Sh BUGS
There is no means for the daemon to tell when a monitored host has
disappeared permanently (eg. catastrophic harware failure), as opposed
to transient failure of the host or an intermediate router.  At present,
it will re-try notification attempts at frequent intervals for 10 minutes,
then hourly, and finally gives up after 24 hours.

The protocol requires that symmetric monitor requests are made to both
the local and remote daemon in order to establish a monitored relationship.
This is convenient for the NFS locking protocol, but probably reduces the
usefulness of the monitoring system for other applications.

The current implementation uses more than 1Kbyte per monitored host in
the status file (and also in VM).  This may be inefficient for NFS servers
with large numbers of clients.
.Sh STANDARDS
The implementation is based on the specification in X/Open CAE Specification
C218, "Protocols for X/Open PC Interworking: XNFS, Issue 4", ISBN 1 872630 66 9