NAME

       axfrdns - a DNS zone-transfer server.

DESCRIPTION

       axfrdns  reads  a zone-transfer request in DNS-over-TCP format from its standard input, and responds with
       locally configured information.

Configuration

       Normally axfrdns is set up by the axfrdns-conf(8) program.

       axfrdns runs chrooted in the directory specified by the $ROOT environment variable, under the uid and gid
       specified by the $UID and $GID environment variables.

       Normally axfrdns runs under tcpserver(1) to handle TCP connections on port 53 of a local IP address.

       tcpserver(1) is responsible  for  rejecting  connections  from  hosts  not  authorized  to  perform  zone
       transfers.

       axfrdns can also run under secure connection tools offering an UCSPI-compliant interface.

       axfrdns  looks  up  zone-transfer results in data.cdb, a binary file created by tinydns-data(8).  It also
       responds to normal client queries, such as SOA queries, which usually precede zone-transfer requests.

       axfrdns allows zone transfers for any zone listed in the $AXFR environment variable.

       $AXFR is a slash-separated list of domain names.  If $AXFR is not set, axfrdns allows zone transfers  for
       all zones available in data.cdb.

       axfrdns  aborts  if  it runs out of memory, or has trouble reading data.cdb, or receives a request larger
       than 512 bytes, or receives a truncated request, or receives a zone-transfer request disallowed by $AXFR,
       or receives a request not answered by data.cdb, or waits 60 seconds with nothing happening.

Further notes on zone transfers

       axfrdns provides every record it can find inside the target domain.  This may include  records  in  child
       zones.  Some of these records (such as glue inside a child zone) are essential; others are not.  It is up
       to the client to decide which out-of-zone records to keep.

       axfrdns does not provide glue records outside the target domain.

       The  zone-transfer  protocol  does not support timestamps.  If a record is scheduled to be created in the
       future, axfrdns does not send it; after  the  starting  time,  the  zone-transfer  client  will  continue
       claiming  that  the  record  doesn't  exist,  until it contacts axfrdns again.  Similarly, if a record is
       scheduled to die in the future, axfrdns sends it (with a 2-second TTL); after the ending time, the  zone-
       transfer client will continue providing the old record, until it contacts axfrdns again.

       Zone-transfer clients rely on zone serial numbers changing for every zone modification.

       tinydns-data(8)  uses  the modification time of the data file as its serial number for all zones.  Do not
       make more than one modification per second.

       BIND's zone-transfer client, named-xfer, converts zone-transfer data to zone-file  format.   Beware  that
       zone-file format has no generic mechanism to express records of arbitrary types;

       named-xfer chokes if it does not recognize a record type used in data.cdb.

SEE ALSO

       axfrdns-conf(8), tinydns-data(8), tcpserver(1)

       http://cr.yp.to/djbdns.html

                                                                                                      axfrdns(8)