RWHOD(ADMN)                        UNIX System V



     Name
          rwhod - system status server


     Syntax
          /etc/rwhod


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

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

          The server transmits  and  receives  messages  at  the  port
          indicated   in   the   rwho   service   specification;   see
          services(SFF).  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 {
                    structoutmp 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
          uptime(C) 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(SLIB) 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(M) 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  5
          minutes.   rwhod  performs  an  nlist(S)  on  /unix every 30
          minutes to guard against the possibility that this  file  is
          not the system image currently operating.


     See Also
          rwho(TC), ruptime(TC).


     Notes
          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  communication failures as a
          machine going down.

          Some mechanism for cleaning dead machine  data  out  of  the
          spool directory is needed.


     (printed 8/17/89)                                  RWHOD(ADMN)