rwhod(1M)              UNIX System V(Internet Utilities)              rwhod(1M)


NAME
      rwhod, in.rwhod - system status server

SYNOPSIS
      in.rwhod

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

      rwhod operates as both a producer and consumer of status information.  As
      a producer of information it periodically queries the state of the system
      and constructs status messages which are broadcast 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/spool/rwho.

      The rwho server transmits and receives messages at the port indicated in
      the rwho service specification, see services(4).  The messages sent and
      received, are of the form:
            struct      outmp {
                  char  outline[8];      /* tty name */
                  char  outname[8];      /* user id */
                  long  outtime;   /* time on */
            };

            struct      whod {
                  char  wdvers;
                  char  wdtype;
                  char  wdfill[2];
                  int   wdsendtime;
                  int   wdrecvtime;
                  char  wdhostname[32];
                  int   wdloadav[3];
                  int   wdboottime;
                        struct      whoent {
                        struct      outmp weutmp;
                        int   weidle;
                  } wdwe[1024 / sizeof (struct whoent)];
            };

      All fields are converted to network byte order prior to transmission.
      The load averages are as calculated by the w(1) program, and represent
      load averages over the 5, 10, and 15 minute intervals prior to a server's
      transmission.  The host name included is that returned by the
      gethostname(2) system call.  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 utmp(4) entry for each non-idle
      terminal line and a value indicating the time since a character was last
      received on the terminal line.



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rwhod(1M)              UNIX System V(Internet Utilities)              rwhod(1M)


      Messages received by the rwho server are discarded unless they originated
      at a rwho server's port.  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/spool/rwho.  These files contain only
      the most recent message, in the format described above.

      Status messages are generated approximately once every 60 seconds.  rwhod
      performs an nlist(3) on /stand/unix every 10 minutes to guard against the
      possibility that this file is not the system image currently operating.

FILES
      /var/spool/rwho

SEE ALSO
      rwho(1), ruptime(1), w(1), gethostname(3), nlist(3), utmp(4)

NOTES
      This service takes up progressively more network bandwidth as the number
      of hosts on the local net increases.  For large networks, the cost
      becomes prohibitive.

      rwhod should relay status information between networks.  People often
      interpret the server dying as a machine going down.

      For rwho to work properly, the directory /var/spool/rwho must exist on
      the system.



























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