202 lines
6.1 KiB
Groff
202 lines
6.1 KiB
Groff
.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)rwhod.8 8.2 (Berkeley) 12/11/93
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.\"
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.Dd December 11, 1993
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.Dt RWHOD 8
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.Os BSD 4.2
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.Sh NAME
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.Nm rwhod
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.Nd system status server
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.Sh SYNOPSIS
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.Nm rwhod
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.Op Fl m Op Ar ttl
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.Sh DESCRIPTION
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.Nm Rwhod
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is the server which maintains the database used by the
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.Xr rwho 1
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and
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.Xr ruptime 1
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programs. Its operation is predicated on the ability to
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.Em broadcast
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or
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.Em multicast
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messages on a network.
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.Pp
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.Nm Rwhod
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operates as both a producer and consumer of status information.
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As a producer of information it periodically
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queries the state of the system and constructs
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status messages which are broadcasted or multicasted on a network.
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As a consumer of information, it listens for other
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.Nm
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servers' status messages, validating them, then recording
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them in a collection of files located in the directory
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.Pa /var/rwho .
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.Pp
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The
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.Fl m
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option causes
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.Nm
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to use IP multicast (instead of
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broadcast) on all interfaces that have
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the IFF_MULTICAST flag set in their "ifnet" structs
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(excluding the loopback interface). The multicast
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reports are sent with a time-to-live of 1, to prevent
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forwarding beyond the directly-connected subnet(s).
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.Pp
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If the optional
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.Ar ttl
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argument is supplied with the
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.Fl m
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flag,
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.Nm
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will send IP multicast datagrams with a
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time-to-live of
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.Ar ttl ,
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via a SINGLE interface rather
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than all interfaces.
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.Ar ttl
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must be between 0 and
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32 (or MAX_MULTICAST_SCOPE). Note that
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.Fl m Ar 1
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is different than
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.Fl m ,
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in that
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.Fl m Ar 1
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specifies transmission on one interface only.
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.Pp
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When
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.Fl m
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is used without a
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.Ar ttl
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argument, the program accepts multicast
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.Nm
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reports from all multicast-capable interfaces. If a
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.Ar ttl
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argument is given, it accepts multicast reports from only one interface, the
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one on which reports are sent (which may be controlled via the host's routing
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table). Regardless of the
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.Fl m
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option, the program accepts broadcast or
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unicast reports from all interfaces. Thus, this program will hear the
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reports of old, non-multicasting
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.Nm rwhod Ns s ,
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but, if multicasting is used,
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those old
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.Nm rwhod Ns s
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won't hear the reports generated by this program.
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.Pp
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The server transmits and receives messages at the port indicated
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in the ``who'' service specification; see
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.Xr services 5 .
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The messages sent and received, are of the form:
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.Bd -literal -offset indent
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struct outmp {
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char out_line[8]; /* tty name */
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char out_name[8]; /* user id */
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long out_time; /* time on */
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};
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struct whod {
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char wd_vers;
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char wd_type;
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char wd_fill[2];
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int wd_sendtime;
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int wd_recvtime;
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char wd_hostname[32];
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int wd_loadav[3];
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int wd_boottime;
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struct whoent {
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struct outmp we_utmp;
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int we_idle;
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} wd_we[1024 / sizeof (struct whoent)];
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};
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.Ed
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.Pp
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All fields are converted to network byte order prior to
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transmission. The load averages are as calculated by the
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.Xr w 1
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program, and represent load averages over the 5, 10, and 15 minute
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intervals prior to a server's transmission; they are multiplied by 100
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for representation in an integer. The host name
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included is that returned by the
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.Xr gethostname 3
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system call, with any trailing domain name omitted.
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The array at the end of the message contains information about
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the users logged in to the sending machine. This information
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includes the contents of the
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.Xr utmp 5
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entry for each non-idle terminal line and a value indicating the
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time in seconds since a character was last received on the terminal line.
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.Pp
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Messages received by the
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.Nm rwho
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server are discarded unless they originated at an
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.Nm rwho
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server's port. In addition, if the host's name, as specified
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in the message, contains any unprintable
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.Tn ASCII
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characters, the
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message is discarded. Valid messages received by
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.Nm
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are placed in files named
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.Pa whod.hostname
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in the directory
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.Pa /var/rwho .
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These files contain only the most recent message, in the
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format described above.
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.Pp
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Status messages are generated approximately once every
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3 minutes.
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.Nm Rwhod
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performs an
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.Xr nlist 3
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on
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.Pa /kernel
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every 30 minutes to guard against
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the possibility that this file is not the system
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image currently operating.
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.Sh SEE ALSO
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.Xr ruptime 1 ,
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.Xr rwho 1
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.Sh BUGS
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Status information should be sent only upon request rather than continuously.
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People often interpret the server dying
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or network communication failures
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as a machine going down.
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.Sh HISTORY
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The
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.Nm
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command appeared in
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.Bx 4.2 .
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