rwhod(1M)

NAME
     rwhod - system status server

SYNOPSIS
     /usr/etc/rwhod [ -m [ ttl ] ]

DESCRIPTION
     Rwhod is the server which maintains the database used by the rwho(1C) and
     ruptime(1C) programs.  Its operation is predicated on the ability to
     broadcast or multicast messages on a network.  Rwhod is started at system
     initialization if the configuration flag rwhod is set ``on'' with
     chkconfig(1M).  Site-dependent options and arguments to rwhod belong in
     the file /etc/config/rwhod.options.

     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 or multicast 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 /usr/spool/rwho.

     The server transmits and receives messages at the port indicated in the
     ``rwho'' service specification; see services(4).  The messages sent and
     received, are defined in <protocols/rwhod.h>:

     struct    outmp {
          char out_line[8]; /* tty name */
          char out_name[8]; /* user id */
          long out_time;    /* time on */
     };

     struct    whod {
          char wd_vers;     /* protocol version # */
          char wd_type;     /* packet type: WHODTYPE_STATUS */
          char wd_pad[2];
          int  wd_sendtime; /* time stamp by sender */
          int  wd_recvtime; /* time stamp applied by receiver */
          char wd_hostname[32];/* host's name */
          int  wd_loadav[3];/* load average as in uptime */
          int  wd_boottime; /* time system booted */
          struct            whoent {
               struct outmp we_utmp;/* active tty info */
               int we_idle; /* tty idle time */
          } wd_we[1024 / sizeof (struct whoent)];
     };


     All fields are converted to network byte order prior to transmission.
     The load averages represent smoothed CPU loads 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(2) 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 utmp(4) 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.  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 /usr/spool/rwho.  These files contain only
     the most recent message, in the format described above.

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

     Rhwod recognizes the following options:

     -m   causes rwhod to use IP multicast (instead of broadcast or unicast)
          on all multicast-capable interfaces (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).

     -m ttl
          causes rwhod to send IP multicast datagrams with a time-to-live of
          ttl, via the default multicast interface only rather than all
          interfaces.  ttl must be between 0 and 32.  Note that "-m 1" is
          different than "-m", in that "-m 1" specifies transmission on one
          interface only.  This allows the information to be relayed between
          networks.

     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 rwhod's, but, if multicasting is used,
     those old rwhod's won't hear the reports generated by this program.

SEE ALSO
     rwho(1C), ruptime(1C), rup(1C)

BUGS
     Status information should be sent only upon request rather than
     continuously.  People often interpret the server dying or network
     communication failures as a machine going down.