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RWHOD(8C)                                                            RWHOD(8C)

       rwhod - system status server


       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 /usr/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 {
                 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 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(5)  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  /usr/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(3) on /vmunix every 10 minutes to guard against
       the possibility that this file is not the system image currently  oper-

       rwho(1C), ruptime(1C)

       Should  relay status information between networks.  People often inter-
       pret the server dieing as a machine going down.

4th Berkeley Distribution        4 March 1983                        RWHOD(8C)