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Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" from: @(#)rwhod.8 6.5 (Berkeley) 3/16/91 .\" $Id: rwhod.8,v 1.16 2000/07/30 23:57:06 dholland Exp $ .\" .\" Modified by Philippe Troin : added interface .\" options and forwarding. .Dd March 10, 1999 .Dt RWHOD 8 .Os "Linux NetKit (0.17)" .Sh NAME .Nm rwhod .Nd system status server .Sh SYNOPSIS .Nm rwhod .Op Fl bpaf .Op -i ... .Op Fl u Ar user .Sh DESCRIPTION .Nm Rwhod is the server which maintains the database used by the .Xr rwho 1 and .Xr ruptime 1 programs. Its operation is predicated on the ability to .Em broadcast messages on a network. .Pp .Nm 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 .Nm rwhod servers' status messages, validating them, then recording them in a collection of files located in the directory .Pa /var/spool/rwho . .Pp The server transmits and receives messages at the port indicated in the ``rwho'' service specification; see .Xr services 5 . .Pp The messages sent and received, are of the form: .Bd -literal -offset indent 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)]; }; .Ed .Pp All fields are converted to network byte order prior to transmission. The load averages are as calculated by the .Xr 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 integer. The host name included is that returned by the .Xr gethostname 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 .Xr 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. .Pp Messages received by the .Xr rwho server are discarded unless they originated at an .Xr rwho server's port. In addition, if the host's name, as specified in the message, contains any unprintable .Tn ASCII characters, the message is discarded. Valid messages received by .Nm rwhod are placed in files named .Pa whod.hostname in the directory .Pa /var/spool/rwho . These files contain only the most recent message, in the format described above. .Pp Status messages are generated approximately once every 3 minutes. .Nm Rwhod recomputes the system boot time every 30 minutes because on some (non-Linux) systems it is not a totally reliable process. .Sh FLAGS If the .Fl b flag is supplied, only broadcast interfaces, such as ethernets, will be used. If the .Fl p flag is supplied, only point-to-point interfaces will be used. If the .Fl a flag is supplied, or no flags are supplied, all interfaces will be used. .Pp Alternately, you may specify interfaces by name by providing one or more .Fl i options followed by the interface name. .Pp If the .Fl 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. .Pp .Nm Rwhod can also forward packets between interfaces if started with .Fl f. Please read the .Xr CAVEATS section before enabling .Xr rwhod forwarding. .Sh CAVEATS While .Xr rwhod listens on any interface present on the host, it will only send (or forward) to the interfaces determined by the .Fl a b p i flags. .Pp When operating in forwarding mode (with .Fl f ), .Xr 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 happenning, .Xr rwhod will shut down forwarding (and log the event to the syslog) if more than one .Xr rwhod packet is forwarded per second on average over the last three minutes. If this happens, you must break the loop of forwarding routers. .Sh SEE ALSO .Xr rwho 1 , .Xr ruptime 1 .Sh BUGS Some kind of proxying feature might be useful if your router doesn't run .Xr rwhod. .Pp People often interpret the server dying or network communication failures as a machine going down. .Pp .Xr Rwhod doesn't refresh its interface list, which might be useful when using .Fl a b p. .Sh HISTORY The .Nm command appeared in .Bx 4.2 . .Pp Philippe Troin implemented forwarding and interface selection flags.