# rarpd(8)

    NAME
         rarpd - reverse address resolution protocol daemon

    SYNOPSIS
         rarpd [-d]

    DESCRIPTION
         Rarpd listens on the ethernet for broadcast packets  asking  for  reverse
         address resolution.  These packets are sent by hosts at boot time to find
         out their IP address.  Rarpd looks up the six octet  ethernet  number  in
         the /etc/ethers file finding a host name.  This name is translated to the
         IP address of the host by a DNS lookup.  The IP address is then  sent  to
         the host.

         Before rarpd can start its  service  it  first  finds  out  what  the  IP
         addresses  of the ethernets are.  It will look through /etc/ethers to map
         the ethernet addresses to host names.  It then uses /etc/hosts to map the
         host  names  to  IP  addresses.   If  this lookup fails then several RARP
         requests are broadcasted in the hope that  some  RARP  server  knows  the
         addresses.   The  IP  addresses  are  eventually  set  in the same way as
         ifconfig(8).  (The address is not changed if already set with  ifconfig.)
         Note  that  the  host  names  in  the  ethers  and hosts files must match
         exactly.  The DNS can not  be  used  yet,  so  a  simple  name  can't  be
         translated to a fully qualified name.

         Once the addresses are configured rarpd  will  figure  out  the  netmasks
         associated  by these addresses.  It will do this by repeatedly looking up
         the netmask corresponding to an interfaces' network  address:  ip-address
         AND  current-netmask.   Once  the  netmask  stops  changing  the  network
         interface is configured with this netmask.  Suppose for example that  the
         address  for an interface is 172.16.102.65.  The initial netmask for this
         class B address is 255.255.0.0.  So we look  up  the  netmask  associated
         with  172.16.0.0  (172.16.102.65  &  255.255.0.0).   This  lookup  yields
         255.255.255.0, so now  look  up  172.16.102.0  to  find  255.255.255.224.
         Lastly  we  look up 172.16.102.64 to find 255.255.255.224 again so we use
         it to set the netmask.

         If rarpd determines that the machine has no real ethernet connection then
         it  will  configure  the default network to have IP address 10.0.0.1 with
         netmask 255.0.0.0.

         Rarpd exits after startup if there are no active ethernets, or  if  there
         is no ethers file.

         Warning! Sun diskless workstations assume that the first RARP server that
         answers  is  the  host they are to boot from.  For this to work all other
         Sun RARP servers delay their answer if they are not also  the  requestors
         boot  server.   The  Minix  rarpd  does  not  have this kludge so it will
         happily engage the Sun boot server to  see  who  can  answer  the  client
         first.   Unless your Minix host can actually serve a Sun diskless client,
         it is better not  to  list  any  more  hosts  in  the  ethers  file  than
         necessary.

    OPTIONS

         -d   Turns on debugging messages.  Debugging can also  be  turned  on  at
              runtime by sending signal SIGUSR1 or turned off with SIGUSR2.

    SEE ALSO
         ifconfig(8),  ethers(5),  hosts(5),  netdefault(8),  boot(8),   inetd(8),
         irdpd(8), nonamed(8).

    AUTHOR
         Kees J. Bot (kjb@cs.vu.nl)