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RWHOD(8)                                 BSD System Manager's Manual                                RWHOD(8)

NAME
     rwhod -- system status server

SYNOPSIS
     rwhod [-i] [-p] [-l] [-m [ttl]]

DESCRIPTION
     The rwhod utility is the server which maintains the database used by the rwho(1) and ruptime(1) pro-grams. programs.
     grams.  Its operation is predicated on the ability to broadcast or multicast messages on a network.

     The rwhod utility operates as both a producer and consumer of status information, unless the -l (listen
     mode) option is specified, in which case it acts as a consumer only.  As a producer of information it
     periodically queries the state of the system and constructs status messages which are broadcasted or
     multicasted on a network.  As a consumer of information, it listens for other rwhod servers' status
     messages, validating them, then recording them in a collection of files located in the directory
     /var/rwho.

     The following options are available:

     -i      Enable insecure mode, which causes rwhod to ignore the source port on incoming packets.

     -p      Ignore all POINTOPOINT interfaces.  This is useful if you do not wish to keep dial on demand
             interfaces permanently active.

     -l      Enable listen mode, which causes rwhod to not broadcast any information.  This allows you to
             monitor other machines' rwhod information, without broadcasting your own.

     -m [ttl]
             Cause rwhod to use IP multicast (instead of broadcast) on all interfaces that have the IFF_MUL-TICAST IFF_MULTICAST
             TICAST flag set in their "ifnet" structs (excluding the loopback interface).  The multicast
             reports are sent with a time-to-live of 1, to prevent forwarding beyond the directly-connected
             subnet(s).

             If the optional ttl argument is supplied with the -m flag, rwhod will send IP multicast data-grams datagrams
             grams with a time-to-live of ttl, via a SINGLE interface rather than all interfaces.  ttl must
             be between 0 and 32 (or MAX_MULTICAST_SCOPE).  Note that -m 1 is different from -m, in that -m
             1 specifies transmission on one interface only.

             When -m is used without a ttl argument, the program accepts multicast rwhod reports from all
             multicast-capable interfaces.  If a ttl argument is given, it accepts multicast reports from
             only one interface, the one on which reports are sent (which may be controlled via the host's
             routing table).  Regardless of the -m option, the program accepts broadcast or unicast reports
             from all interfaces.  Thus, this program will hear the reports of old, non-multicasting rwhods,
             but, if multicasting is used, those old rwhods will not hear the reports generated by this pro-gram. program.
             gram.

     The server transmits and receives messages at the port indicated in the ``who'' service specification;
     see services(5).  The messages sent and received, are of the form:

           struct  outmp {
                   char    out_line[8];            /* tty name */
                   char    out_name[8];            /* user id */
           #ifdef __LP64__
                   int     out_time;               /* time on */
           #else /* !__LP64__ */
                   long    out_time;               /* time on */
           #endif /* __LP64__ */
           };

           struct  whod {
                   char    wd_vers;
                   char    wd_type;
                   char    wd_fill[2];
                   int     wd_sendtime;
                   int     wd_recvtime;
                   char    wd_hostname[32];
                   int     wd_loadav[3];
                   int     wd_boottime;
                   struct  whoent {
                           struct  outmp we_utmp;
                           int     we_idle;
                   } wd_we[1024 / sizeof (struct whoent)];
           };

     All fields are converted to network byte order prior to transmission.  The load averages are as calcu-lated calculated
     lated by the w(1) program, and represent load averages over the 5, 10, and 15 minute intervals prior to
     a server's transmission; they are multiplied by 100 for representation in an integer.  The host name
     included is that returned by the gethostname(3) system call, with any trailing domain name omitted.
     The array at the end of the message contains information about the users logged in to the sending
     machine.  This information includes the contents of the utmpx(5) entry for each non-idle terminal line
     and a value indicating the time in seconds since a character was last received on the terminal line.

     Messages received by the rwho server are discarded unless they originated at an rwho server's port or
     the -i option was specified.  In addition, if the host's name, as specified in the message, contains
     any unprintable ASCII characters, the message is discarded.  Valid messages received by rwhod are
     placed in files named whod.hostname in the directory /var/rwho.  These files contain only the most
     recent message, in the format described above.

     Status messages are generated approximately once every 3 minutes.  The rwhod utility performs an
     nlist(3) on /boot/kernel/kernel every 30 minutes to guard against the possibility that this file is not
     the system image currently operating.

SEE ALSO
     ruptime(1), rwho(1)

HISTORY
     The rwhod utility appeared in 4.2BSD.

BUGS
     There should be a way to relay status information between networks.  Status information should be sent
     only upon request rather than continuously.  People often interpret the server dying or network commu-nication communication
     nication failures as a machine going down.

BSD                                           December 11, 1993                                          BSD