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RWHOD(8C)                                                            RWHOD(8C)

       rwhod, in.rwhod - system status server


       Due  to  its  potential  impact on network performance, this service is
       commented out of the /etc/rc system initialization script.  It is  pro-
       vided only for 4.3 BSD compatibility.

       This  program  is  available  with the Networking software installation
       option.  Refer to for information on how to install optional software.

       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 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' sta-
       tus 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(5).   The  messages
       sent and received, are of the form:
              struct    outmp {
                     char out_line[8];   /* tty name */
                     char out_name[8];   /* user id */
                     long out_time; /* time on */

              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 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 con-
       tains information about the users logged in  to  the  sending  machine.
       This  information  includes the contents of the utmp(5V) entry for each
       non-idle terminal line and a value indicating the time since a  charac-
       ter was last received on the terminal line.

       Messages  received  by the rwho server are discarded unless they origi-
       nated 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

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


       rwho(1C), ruptime(1C), w(1), gethostname(2), nlist(3V), utmp(5V),  sys-

       Status and diagnostic messages are logged to the appropriate system log
       using the syslogd(8) facility.

       This service takes up progressively more network bandwidth as the  num-
       ber  of hosts on the local net increases.  For large networks, the cost
       becomes prohibitive.  RPC-based services such as rup(1C) and rusers(1C)
       provide a similar function with greater efficiency.

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

                               17 December 1987                      RWHOD(8C)