RWHOD(8)                 UNIX System Manager's Manual                 RWHOD(8)

NAME
     rwhod - system status server

SYNOPSIS
     rwhod [-bpa]

DESCRIPTION
     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 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' status mes-
     sages, validating them, then recording them in a collection of files lo-
     cated in the directory /var/spool/rwho.

     The server transmits and receives messages at the port indicated in the
     ``rwho'' service specification; see services(5).

     If the -b flag is supplied, only broadcast interfaces, such as ethernets,
     will be used.  If the -p flag is supplied, only point-to-point interfaces
     will be used. If the -a flag is supplied, or no flags are supplied, all
     interfaces will be used.

     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 {
                           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 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 gethostname(2) sys-
     tem 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/spool/rwho. These files contain only
     the most recent message, in the format described above.

     Status messages are generated approximately once every 3 minutes.  Rwhod
     recomputes the system boot time every 30 minutes because on some (non-
     Linux) systems it is not a totally reliable process.

SEE ALSO
     rwho(1),  ruptime(1)

BUGS
     There should be a way to relay status information between networks.  Peo-
     ple often interpret the server dying or network communtication failures
     as a machine going down.

HISTORY
     The rwhod command appeared in 4.2BSD.

 Linux 2.0                       May 13, 1997                                1