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GENDNS(1)			   06:53:19			     GENDNS(1)

       gendns - update the DNS zone files from flat relational tables

       gendns [ -d dbdirectory ] [ -l dhcp_lease_file [ -v ] [ -F ]

       Updates the DNS zone files.

       gendns  is  a  back end to the updatehosts command.  It should normally
       only be invoked from the updatehosts command.

       gendns converts a set of flat (relational) files into the standard  DNS
       zone  file  format.   All input files are kept in the dbdirectory which
       can be specified by the -d command line option.	All output  is	placed
       in  the	current  directory.   When  run  under updatehosts the current
       directory is normally /var/named and the input  directory  is  normally
       /var/named/db.	However,  these  defaults  may be overridden.  See the
       updatehosts(1) manual page for details.

       The -l option specifies	the  location  of  the	dhcp_lease  file.   It
       defaults  to  /etc/dhcpd.leases.   gendns has the capability of reading
       the lease file information and generating name to IP  address  mappings
       when the IP address of a host is set to "dynamic".

       The  -v	option generates additional output on the progress of the zone
       file generation.

       The -F option forces a zone files serial  number  to  be  updated  even
       though  no  changes  were  made to the zone file.  This was the default
       behavior before updatehosts 1.0.2.  Now if the information  in  a  zone
       file does not change, the zone files serial number is not not updated.
       This saves slave zone transfers when updatehosts handles a large number
       of zone files.

Input File Formats
       gendns  uses  readinfo (see readinfo(1)) to preprocess the input files.
       The format of each file consists of a set  of  records  separated  into
       fields.	 Care  should  be  taken  to  insure  the  field names are not
       altered.  Otherwise  gendns  will  complain.   Each  fields  attributes
       should  be  examined  carefully when editing the input files.  Usually,
       default suffixes  and  prefixes	are  added  so	domain	names  and  IP
       addresses  can  be written in a shorthand fashion.  However, the output
       from readinfo read by gendns is expected to have fully qualified domain
       names  and full dotted quad IP addresses.  Each files record structure
       is described as follows:

       main:  Contains information about each host.  The fields in  this  file
	      are as follows:

	      host:  The domain name of the host.

	      ip:    The IP address of the host.  May be set to "dynamic" when
		     the dynamic addressing of DHCP is in use.

	      ether: The hardware MAC address of the host.

	      hard:  The hardware type of the host.

	      os:    The operating system of the host.

		     The name of a contact person or user of the host.

	      ptr:   Either "yes" or "no". Tells gendns  whether  to  generate
		     the  reverse  zone entry for the host (e.g.the IP address
		     to domain mapping zone). The  default  (empty)  value  is

	      ttl:   Specifies	the time to live field for both the address (A
		     record type) and the reverse  PTR	record	if  generated.
		     Time is specified in seconds.  If this field is empty the
		     default ttl for the zone (specified in the SOA record) is

       gendns  only  needs  entries  for  the domain and ip fields.  The other
       fields may be empty.

       cname: Species information about hosts and their aliases.   The	fields

	      host:  The domain name of a host

	      alias: The alias for the host

	      ttl:   The time to live for this record

       mx:    Specifies information about MX (mail exchanger) records.

		     The mail domain name

		     The MX record priority

	      host:  The domain name of the mail forwarder

	      ttl:   The time to live for this record

       ns:    Specifies information about nameserver records.

		     The nameserver domain

		     The domain name of the server for each domain

	      ttl:   The time to live for this record

       soa:   The SOA (start of authority)  record information for each domain

		     The domain (zone) this server is authoritative for

		     The domain name of the primary server for this domain

		     Email address of domain contact.  Per  DNS  format  rules
		     the @ in the address is specified as a ".".

		     The refresh interval for this zone in seconds

	      retry: The retry interval for this zone in seconds

		     The  authoritative  expiration  time  in seconds for sec
		     ondary servers which have not been refreshed  within  the
		     interval specified.

	      min:   The minimum time to live for resource records within this
		     zone without a ttl.

		     Specifies how illegal domain  names  are  treated	within
		     this  zone.  Only	works  with  version 8 of bind.  The 3
		     legal values of this field are:

		      warn:  Warns about illegal names, but allows  the  names
			     within  a	zone. Emits an error message about the

			     Ignores illegal names within the zone.

		      fail:  Emits error messages about illegal names and does
			     not load the zone.

		     If  this  field is "yes", all secondary servers are noti
		     fied about updates.  Only works with Version 8 of bind.

	      Specifies zones this server will act as a secondary server  for.
	      In bind version 8 a secondary server is known as a slave server.

		     The name of the domain being served.

	      ip:    The IP address of an authoritative server for this  zone.
		     Multiple  servers	may  be specified by separating the IP
		     address with commas.

		     Same values as the checknames field in the soa records.

	      Contains global parameters applicable to all zones.

		     The name of the directory containing the  generated  zone

	      cache: Name of the root cache file

		     list  of  optional forwarders for this server. This field
		     is usually empty

		     Same as the checknames field  found  in  each  zone,  but
		     applies to all zones.  Individual zones may override this

	      slave: Sets up this server as a slave server (stub in bind  ver
		     sion  8  parlance).   Can	be  either  "yes" or "no". The
		     default is "no".

Zone File Generation
       Zone file generation is driven off of the soa file.  Each domain speci
       fied  in  the soa file generates a separate DNS zone file.  The name of
       the zone file is the same as the name of the domain field  for  forward
       zones.	For  a	zone  under in-addr.arpa (e.g. IP address to name map
       ping), the name of the zone file is the IP network address of the  zone
       with  an "f." prefix.  For classless in-addr.arpa delegation of Class C
       addresses, the assumption is the delegation is done per	RFC2317.   The
       zone file name replaces the "/" in the delegation reference with a "-".
       For example delegating the subnet of means delegating the
       zone  2/   The zone file in this case would be
       named f.  A zone file is only generated if it appears  in
       the  soa  file.	Records in the other input files which are not members
       of a generated zone are silently ignored.

       The program scans all the input files for domain  records  within  each
       zone and generates all the records for the zone.

       The  serial  number  field  is updated automatically for each new zone.
       The serial number is encoded from the real time clock value as yyyymmd
       dxx, where yyyy is the 4 digit year, mm is the 2 digit month, dd is the
       2 digit day, and xx is a 2 digit number between 00 and 99.  This  gives
       a granularity between updates of about 15 minutes.

Bootstrap File Generation
       gendns  also  generates the bootstrap file for either version 4 or ver
       sion 8 of the bind nameserver.  The generated bootstrap file is put  in
       the current directory (usually /var/named).  To allow the nameserver to
       use the newly generated bootstrap file it is customary to  link	it  to
       either  /etc/named.boot	for  a version 4 nameserver or /etc/named.conf
       for a version 8 nameserver.

Error Handling
       An error message is issued for any CNAME (alias) record which is  ille
       gal.  A CNAME record must only appear at a leaf node in the DNS hierar
       chy. Any record which violates this rule is dropped.  A warning message
       is  issued  for any duplicate IP address or duplicate A records.  These
       are warnings only, since duplication of domain names  or  IP  addressed
       may be desirable.

See also

4th Berkeley Distribution	    $Date:			     GENDNS(1)

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