RWHOD(8C)                            BSD                             RWHOD(8C)



NAME
     rwhod - system status server

SYNOPSIS
     /etc/rwhod [ -w ]

DESCRIPTION
     The rwhod server 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.

     On Apollo networks, rwhod has been changed to take advantage of the
     Domain distributed file system and to reduce contention for the rwho
     directory.  Since on Apollo networks, there is no need for every host on
     the network to maintain its own /usr/spool/rwho directory, a change has
     been made to allow you to specify one host per network who will write the
     information to a master /usr/spool/rwho directory.  All the other hosts
     link to that master directory to access the information but do not write
     to the directory.  Specifically, rwhod writes to /usr/spool/rwho only if
     that directory is local to the node, or if the optional -w switch is
     supplied.

     rwhod both produces and consumes system status information.  It
     periodically queries the state of the system and constructs status
     messages which are broadcast on a network, and it listens for other rwhod
     servers' status messages as well.  When it receives a status message from
     another server, rwhod validates it and records it in a file located in
     the directory /usr/spool/rwho, if the directory is physically located on
     the host or if rwhod was started with the -w switch.  On hosts where
     rwhod was started without the -w switch and where /usr/spool/rwho is a
     link to a remote host, rwhod does not write to the directory.

     The rwho server transmits and receives messages at the port indicated in
     the "rwho" service specification.  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 before transmission.  The
     load averages represent 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 contains information about the users logged in to the sending
     machine.  This information includes an 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 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.

OPTIONS
     -w        Update the files in the /usr/spool/rwho directory, even if the
               directory is not local to the node.

NOTES
     Note that rwhod will update the files in the /usr/spool/rwho directory in
     two cases:

          1.   If the /usr/spool/rwho directory is physically located
               on that host.

          2.    If rwhod was started with the -w switch.

     To reduce contention for the rwho directory and provide updated
     information to hosts, we recommend that you

     ⊕  Physically locate the /usr/spool/rwho directory on the network's
        TCP/IP administrative node.  All other hosts on the network should be
        set up so that /usr/spool/rwho is a link to the administrative node.

     ⊕  If you are running rwhod in a Domain internet, you can configure your
        network in one of two ways:

          1.   Configure one node on each subnet to have a local /usr/spool/rwho
               and link all other nodes on that subnet to that node.

          2.   Configure all nodes in the internet to link to one master TCP/IP
               administrative node containing the /usr/spool/rwho directory.
               This enables the rwho and ruptime utilities to see all nodes in the
               internet.

               In order to make this arrangement work, you must run rwhod -w on one
               node on each subnet.  They will then write their subnet's information
               to the directory on the internet's master TCP/IP administrative node.

            You also can run rwhod on a gateway to see broadcasts from two
            networks.

     rwhod, like other BSD daemons, is invoked at boot time by the
     /etc/rc.local startup file.  See Configuring and Managing TCP/IP for more
     information about rwhod.

NOTES
     People often interpret the server's dying as a machine in the network
     going down.

SEE ALSO
     rwho(1C), ruptime(1C), rc(8)