in.rwhod(1M)

NAME

     in.rwhod, rwhod - system status server

SYNOPSIS

     /usr/sbin/in.rwhod [ -m [ttl]]

DESCRIPTION

     in.rwhod is the server which maintains the database used  by
     the  rwho(1)  and  ruptime(1)  programs.   Its  operation is
     predicated on the ability to broadcast or multicast messages
     on a network.

     in.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 or multicast on a network. As a
     consumer of  information,  it  listens  for  other  in.rwhod
     servers'  status  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  ser-
     vices(4).  The messages sent and  received  are  defined  in
     /usr/include/protocols/rwhod.h and 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 1, 5, and
     15  minute  intervals prior to a server's transmission.  The
     host name included is that returned by the  uname(2)  system
     call.   The  array  at  the  end  of  the  message  contains
     information about the users who are logged in to the sending
     machine.   This  information  includes  the  contents of the
     utmpx(4) entry for each non-idle terminal line and  a  value
     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 in.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  3
     minutes.

OPTIONS

     The following options are supported:

     -m [ ttl ]
           Use the rwho  IP multicast  address  (224.0.1.3)  when
           transmitting.  Receive announcements both on this mul-
           ticast address and on the  IP  broadcast  address.  If
           ttl  is  not  specified   in.rwhod  multicasts  on all
           interfaces but with the  IP TimeToLive set to 1  (that
           is,  packets  are not forwarded by multicast routers.)
           If  ttl is specified  in.rwhod only transmits  packets
           on one interface and setting the  IP TimeToLive to the
           specified  ttl.

FILES

     /var/spool/rwho/whod.*
           information about other machines

ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | SUNWrcmds                   |
    |_____________________________|_____________________________|

SEE ALSO

     ruptime(1), rwho(1), w(1), uname(2), services(4),  utmpx(4),
     attributes(5)

WARNINGS

     This service can cause  network  performance  problems  when
     used  by several hosts on the network. It is not run at most
     sites by default. If used, include the -m multicast option.

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.

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