rwhod

NAME

       rwhod - system status server

SYNOPSIS

       rwhod

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 messages on a net-
       work.

       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
       messages,  validating  them, then recording them in a col-
       lection of files located in the directory /var/rwho.

       The server transmits and receives  messages  at  the  port
       indicated  in the ``rwho'' service specification; see ser-
       vices(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;
       they  are multiplied by 100 for representation in an inte-
       ger.  The host name included is that returned by the geth-
       ostname(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(5)  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  /var/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 /vmunix every 30
       minutes to guard against the possibility that this file is
       not the system image currently operating.

SEE ALSO

       rwho(1), ruptime(1)

BUGS

       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 communtication failures  as  a
       machine going down.