rwhod man page on Kali

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

NAME
     rwhod — system status server

SYNOPSIS
     rwhod [-bpaf] [-i <if>...] [-u user]

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
     located in the directory /var/spool/rwho.

     The 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 {
			   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.

FLAGS
     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.

     Alternately, you may specify interfaces by name by providing one or more
     -i options followed by the interface name.

     If the -u flag is supplied, rwhod will run as the specified user instead
     of as rwhod. The initial user until the daemon drops privileges is root.

     Rwhod can also forward packets between interfaces if started with -f.
     Please read the CAVEATS section before enabling rwhod forwarding.

CAVEATS
     While rwhod listens on any interface present on the host, it will only
     send (or forward) to the interfaces determined by the -a -b -p -i flags.

     When operating in forwarding mode (with -f ), rwhod forwards all correct
     rwhod packets received on an interface to all the other interfaces. You
     can create a broadcast storm if there is a loop in your network and all
     the routers in the loop run in forwarding mode. To prevent this from hap‐
     penning, rwhod will shut down forwarding (and log the event to the sys‐
     log) if more than one rwhod packet is forwarded per second on average
     over the last three minutes. If this happens, you must break the loop of
     forwarding routers.

SEE ALSO
     rwho(1), ruptime(1)

BUGS
     Some kind of proxying feature might be useful if your router doesn't run
     rwhod.

     People often interpret the server dying or network communication failures
     as a machine going down.

     Rwhod doesn't refresh its interface list, which might be useful when
     using -a -b -p.

HISTORY
     The rwhod command appeared in 4.2BSD.

     Philippe Troin <phil@fifi.org> implemented forwarding and interface
     selection flags.

Linux NetKit (0.17)		March 10, 1999		   Linux NetKit (0.17)
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