rwhod(1M)        SYSTEM ADMINISTRATION COMMANDS         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 predi-
     cated 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  mes-
     sages  which  are  broadcast on a network.  As a consumer of
     information, it listens for other rwhod servers' status mes-
     sages,  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  ser-
     vices(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  gethost-
     name(2)  system  call.   The array at the end of the message
     contains information about the users logged in to the  send-
     ing  machine.  This information includes the contents of the
     utmp(4) entry for each non-idle terminal line  and  a  value



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rwhod(1M)        SYSTEM ADMINISTRATION COMMANDS         rwhod(1M)



     indicating  the  time since a character was last received on
     the terminal line.

     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.























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