bind/dist/FAQ.xml

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<!-- Id: FAQ.xml,v 1.54 2010/01/19 23:48:55 tbox Exp  -->

<article class="faq">
  <title>Frequently Asked Questions about BIND 9</title>
  <articleinfo>
    <copyright>
      <year>2004</year>
      <year>2005</year>
      <year>2006</year>
      <year>2007</year>
      <year>2008</year>
      <year>2009</year>
      <year>2010</year>
      <year>2013</year>
      <year>2014</year>
      <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
    </copyright>
    <copyright>
      <year>2000</year>
      <year>2001</year>
      <year>2002</year>
      <year>2003</year>
      <holder>Internet Software Consortium.</holder>
    </copyright>
  </articleinfo>
  <qandaset defaultlabel='qanda'>

    <qandadiv><title>Compilation and Installation Questions</title>

    <qandaentry>
      <question>
	<para>
	  I'm trying to compile BIND 9, and "make" is failing due to
	  files not being found.  Why?
	</para>
      </question>
      <answer>
	<para>
	  Using a parallel or distributed "make" to build BIND 9 is
	  not supported, and doesn't work.  If you are using one of
	  these, use normal make or gmake instead.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Isn't "make install"  supposed to generate a default named.conf?
	</para>
      </question>
      <answer>
	<para>
	  Short Answer: No.
	</para>
	<para>
	  Long Answer: There really isn't a default configuration which fits
	  any site perfectly.  There are lots of decisions that need to
	  be made and there is no consensus on what the defaults should be.
	  For example FreeBSD uses /etc/namedb as the location where the
	  configuration files for named are stored.  Others use /var/named.
	</para>
	<para>
	  What addresses to listen on?  For a laptop on the move a lot
	  you may only want to listen on the loop back interfaces.
	</para>
	<para>
	  To whom do you offer recursive service?  Is there a firewall
	  to consider?  If so, is it stateless or stateful?  Are you
	  directly on the Internet?  Are you on a private network? Are
	  you on a NAT'd network? The answers
	  to all these questions change how you configure even a
	  caching name server.
	</para>
      </answer>
    </qandaentry>

    </qandadiv> <!-- Compilation and Installation Questions -->

    <qandadiv><title>Configuration and Setup Questions</title>

    <qandaentry>
      <!-- configuration, log -->
      <question>
	<para>
	  Why does named log the warning message <quote>no TTL specified -
	  using SOA MINTTL instead</quote>?
	</para>
      </question>
      <answer>
	<para>
	  Your zone file is illegal according to RFC1035.  It must either
	  have a line like:
	</para>
	<informalexample>
	  <programlisting>
$TTL 86400</programlisting>
	</informalexample>
	<para>
	  at the beginning, or the first record in it must have a TTL field,
	  like the "84600" in this example:
	</para>
	<informalexample>
	  <programlisting>
example.com. 86400 IN SOA ns hostmaster ( 1 3600 1800 1814400 3600 )</programlisting>
	</informalexample>
      </answer>
    </qandaentry>

    <qandaentry>
      <!-- configuration -->
      <question>
	<para>
	  Why do I get errors like <quote>dns_zone_load: zone foo/IN: loading
	  master file bar: ran out of space</quote>?
	</para>
      </question>
      <answer>
	<para>
	This is often caused by TXT records with missing close
	quotes.  Check that all TXT records containing quoted strings
	have both open and close quotes.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <!-- security -->
      <question>
	<para>
	  How do I restrict people from looking up the server version?
	</para>
      </question>
      <answer>
	<para>
	  Put a "version" option containing something other than the
	  real version in the "options" section of named.conf.  Note
	  doing this will not prevent attacks and may impede people
	  trying to diagnose problems with your server.  Also it is
	  possible to "fingerprint" nameservers to determine their
	  version.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <!-- security -->
      <question>
	<para>
	  How do I restrict only remote users from looking up the
	  server version?
	</para>
      </question>
      <answer>
	<para>
	  The following view statement will intercept lookups as the
	  internal view that holds the version information will be
	  matched last.  The caveats of the previous answer still
	  apply, of course.
	</para>
	<informalexample>
	  <programlisting>
view "chaos" chaos {
	match-clients { &lt;those to be refused&gt;; };
	allow-query { none; };
	zone "." {
		type hint;
		file "/dev/null";  // or any empty file
	};
};</programlisting>
	</informalexample>
      </answer>
    </qandaentry>

    <qandaentry>
      <!-- configuration -->
      <question>
	<para>
	  What do <quote>no source of entropy found</quote> or <quote>could not
	  open entropy source foo</quote> mean?
	</para>
      </question>
      <answer>
	<para>
	  The server requires a source of entropy to perform certain
	  operations, mostly DNSSEC related.  These messages indicate
	  that you have no source of entropy.  On systems with
	  /dev/random or an equivalent, it is used by default.  A
	  source of entropy can also be defined using the random-device
	  option in named.conf.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <!-- configuration -->
      <question>
	<para>
	  I'm trying to use TSIG to authenticate dynamic updates or
	  zone transfers.  I'm sure I have the keys set up correctly,
	  but the server is rejecting the TSIG.  Why?
	</para>
      </question>
      <answer>
	<para>
	  This may be a clock skew problem.  Check that the the clocks
	  on the client and server are properly synchronised (e.g.,
	  using ntp).
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I see a log message like the following.  Why?
	</para>
	<para>
	  couldn't open pid file '/var/run/named.pid': Permission denied
	</para>
      </question>
      <answer>
	<para>
	  You are most likely running named as a non-root user, and
	  that user does not have permission to write in /var/run.
	  The common ways of fixing this are to create a /var/run/named
	  directory owned by the named user and set pid-file to
	  "/var/run/named/named.pid", or set pid-file to "named.pid",
	  which will put the file in the directory specified by the
	  directory option (which, in this case, must be writable by
	  the user named is running as).
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I can query the nameserver from the nameserver but not from other
	  machines.  Why?
	</para>
      </question>
      <answer>
	<para>
	  This is usually the result of the firewall configuration stopping
	  the queries and / or the replies.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  How can I make a server a slave for both an internal and
	  an external view at the same time?  When I tried, both views
	  on the slave were transferred from the same view on the master.
	</para>
      </question>
      <answer>
	<para>
	  You will need to give the master and slave multiple IP
	  addresses and use those to make sure you reach the correct
	  view on the other machine.
	</para>
	<informalexample>
	  <programlisting>
Master: 10.0.1.1 (internal), 10.0.1.2 (external, IP alias)
    internal:
	match-clients { !10.0.1.2; !10.0.1.4; 10.0.1/24; };
		notify-source 10.0.1.1;
		transfer-source 10.0.1.1;
		query-source address 10.0.1.1;
    external:
	match-clients { any; };
	recursion no;	// don't offer recursion to the world
	notify-source 10.0.1.2;
	transfer-source 10.0.1.2;
	query-source address 10.0.1.2;

Slave: 10.0.1.3 (internal), 10.0.1.4 (external, IP alias)
    internal:
	match-clients { !10.0.1.2; !10.0.1.4; 10.0.1/24; };
	notify-source 10.0.1.3;
	transfer-source 10.0.1.3;
	query-source address 10.0.1.3;
   external:
	match-clients { any; };
	recursion no;	// don't offer recursion to the world
	notify-source 10.0.1.4;
	transfer-source 10.0.1.4;
	query-source address 10.0.1.4;</programlisting>
	</informalexample>
	<para>
	  You put the external address on the alias so that all the other
	  dns clients on these boxes see the internal view by default.
	</para>
      </answer>
      <answer>
	<para>
	  BIND 9.3 and later: Use TSIG to select the appropriate view.
	</para>
	<informalexample>
	  <programlisting>
Master 10.0.1.1:
	key "external" {
		algorithm hmac-sha256;
		secret "xxxxxxxxxxxxxxxxxxxxxxxx";
	};
	view "internal" {
		match-clients { !key external; // reject message ment for the
					       // external view.
				10.0.1/24; };  // accept from these addresses.
		...
	};
	view "external" {
		match-clients { key external; any; };
		server 10.0.1.2 { keys external; };  // tag messages from the
						     // external view to the
						     // other servers for the
						     // view.
		recursion no;
		...
	};

Slave 10.0.1.2:
	key "external" {
		algorithm hmac-sha256;
		secret "xxxxxxxxxxxxxxxxxxxxxxxx";
	};
	view "internal" {
		match-clients { !key external; 10.0.1/24; };
		...
	};
	view "external" {
		match-clients { key external; any; };
		server 10.0.1.1 { keys external; };
		recursion no;
		...
	};</programlisting>
	</informalexample>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I get error messages like <quote>multiple RRs of singleton type</quote>
	  and <quote>CNAME and other data</quote> when transferring a zone.  What
	  does this mean?
	</para>
      </question>
      <answer>
	<para>
	  These indicate a malformed master zone.  You can identify
	  the exact records involved by transferring the zone using
	  dig then running named-checkzone on it.
	</para>
	<informalexample>
	  <programlisting>
dig axfr example.com @master-server &gt; tmp
named-checkzone example.com tmp</programlisting>
	</informalexample>
	<para>
	  A CNAME record cannot exist with the same name as another record
	  except for the DNSSEC records which prove its existence (NSEC).
	</para>
	<para>
	  RFC 1034, Section 3.6.2: <quote>If a CNAME RR is present at a node,
	  no other data should be present; this ensures that the data for a
	  canonical name and its aliases cannot be different.  This rule also
	  insures that a cached CNAME can be used without checking with an
	  authoritative server for other RR types.</quote>
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I get error messages like <quote>named.conf:99: unexpected end
	  of input</quote> where 99 is the last line of named.conf.
	</para>
      </question>
      <answer>
	<para>
	  There are unbalanced quotes in named.conf.
	</para>
      </answer>
      <answer>
	<para>
	  Some text editors (notepad and wordpad) fail to put a line
	  title indication (e.g. CR/LF) on the last line of a
	  text file.  This can be fixed by "adding" a blank line to
	  the end of the file.  Named expects to see EOF immediately
	  after EOL and treats text files where this is not met as
	  truncated.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  How do I share a dynamic zone between multiple views?
	</para>
      </question>
      <answer>
	<para>
	  You choose one view to be master and the second a slave and
	  transfer the zone between views.
	</para>
	<informalexample>
	  <programlisting>
Master 10.0.1.1:
	key "external" {
		algorithm hmac-sha256;
		secret "xxxxxxxxxxxxxxxxxxxxxxxx";
	};

	key "mykey" {
		algorithm hmac-sha256;
		secret "yyyyyyyyyyyyyyyyyyyyyyyy";
	};

	view "internal" {
		match-clients { !key external; 10.0.1/24; };
		server 10.0.1.1 {
			/* Deliver notify messages to external view. */
			keys { external; };
		};
		zone "example.com" {
			type master;
			file "internal/example.db";
			allow-update { key mykey; };
			also-notify { 10.0.1.1; };
		};
	};

	view "external" {
		match-clients { key external; any; };
		zone "example.com" {
			type slave;
			file "external/example.db";
			masters { 10.0.1.1; };
			transfer-source 10.0.1.1;
			// allow-update-forwarding { any; };
			// allow-notify { ... };
		};
	};</programlisting>
	</informalexample>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I get a error message like <quote>zone wireless.ietf56.ietf.org/IN:
	  loading master file primaries/wireless.ietf56.ietf.org: no
	  owner</quote>.
	</para>
      </question>
      <answer>
	<para>
	  This error is produced when a line in the master file
	  contains leading white space (tab/space) but there is no
	  current record owner name to inherit the name from.  Usually
	  this is the result of putting white space before a comment,
	  forgetting the "@" for the SOA record, or indenting the master
	  file.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Why are my logs in GMT (UTC).
	</para>
      </question>
      <answer>
	<para>
	  You are running chrooted (-t) and have not supplied local timezone
	  information in the chroot area.
	</para>
	<simplelist>
	  <member>FreeBSD: /etc/localtime</member>
	  <member>Solaris: /etc/TIMEZONE and /usr/share/lib/zoneinfo</member>
	  <member>OSF: /etc/zoneinfo/localtime</member>
	  </simplelist>
	<para>
	  See also tzset(3) and zic(8).
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I get <quote>rndc: connect failed: connection refused</quote> when
	  I try to run rndc.
	</para>
      </question>
      <answer>
	<para>
	  This is usually a configuration error.
	</para>
	<para>
	  First ensure that named is running and no errors are being
	  reported at startup (/var/log/messages or equivalent).
	  Running "named -g &lt;usual arguments&gt;" from a title
	  can help at this point.
	</para>
	<para>
	  Secondly ensure that named is configured to use rndc either
	  by "rndc-confgen -a", rndc-confgen or manually.  The
	  Administrators Reference manual has details on how to do
	  this.
	</para>
	<para>
	  Old versions of rndc-confgen used localhost rather than
	  127.0.0.1 in /etc/rndc.conf for the default server.  Update
	  /etc/rndc.conf if necessary so that the default server
	  listed in /etc/rndc.conf matches the addresses used in
	  named.conf.  "localhost" has two address (127.0.0.1 and
	  ::1).
	</para>
	<para>
	  If you use "rndc-confgen -a" and named is running with -t or -u
	  ensure that /etc/rndc.conf has the correct ownership and that
	  a copy is in the chroot area.  You can do this by re-running
	  "rndc-confgen -a" with appropriate -t and -u arguments.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I get <quote>transfer of 'example.net/IN' from 192.168.4.12#53:
	  failed while receiving responses: permission denied</quote> error
	  messages.
	</para>
      </question>
      <answer>
	<para>
	  These indicate a filesystem permission error preventing
	  named creating / renaming the temporary file.  These will
	  usually also have other associated error messages like
	</para>
	<informalexample>
	  <programlisting>
"dumping master file: sl/tmp-XXXX5il3sQ: open: permission denied"</programlisting>
	</informalexample>
	<para>
	  Named needs write permission on the directory containing
	  the file.  Named writes the new cache file to a temporary
	  file then renames it to the name specified in named.conf
	  to ensure that the contents are always complete.  This is
	  to prevent named loading a partial zone in the event of
	  power failure or similar interrupting the write of the
	  master file.
	</para>
	<para>
	  Note file names are relative to the directory specified in
	  options and any chroot directory  ([&lt;chroot
	  dir&gt;/][&lt;options dir&gt;]).
	</para>
	<informalexample>
	  <para>
	    If named is invoked as "named -t /chroot/DNS" with
	    the following named.conf then "/chroot/DNS/var/named/sl"
	    needs to be writable by the user named is running as.
	  </para>
	  <programlisting>
options {
	directory "/var/named";
};

zone "example.net" {
	type slave;
	file "sl/example.net";
	masters { 192.168.4.12; };
};</programlisting>
	</informalexample>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I want to forward all DNS queries from my caching nameserver to
	  another server. But there are some domains which have to be
	  served locally, via rbldnsd.
	</para>
	<para>
	  How do I achieve this ?
	</para>
      </question>
      <answer>
        <programlisting>
options {
	forward only;
	forwarders { &lt;ip.of.primary.nameserver&gt;; };
};

zone "sbl-xbl.spamhaus.org" {
	type forward; forward only;
	forwarders { &lt;ip.of.rbldns.server&gt; port 530; };
};

zone "list.dsbl.org" {
	type forward; forward only;
	forwarders { &lt;ip.of.rbldns.server&gt; port 530; };
};
        </programlisting>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Can you help me understand how BIND 9 uses memory to store
	  DNS zones?
	</para>
	<para>
	  Some times it seems to take several times the amount of
	  memory it needs to store the zone.
	</para>
      </question>
      <answer>
	<para>
	  When reloading a zone named my have multiple copies of
	  the zone in memory at one time.  The zone it is serving
	  and the one it is loading.  If reloads are ultra fast it
	  can have more still.
	</para>
	<para>
	  e.g.  Ones that are transferring out, the one that it is
	  serving and the one that is loading.
	</para>
	<para>
	  BIND 8 destroyed the zone before loading and also killed
	  off outgoing transfers of the zone.
	</para>
	<para>
	  The new strategy allows slaves to get copies of the new
	  zone regardless of how often the master is loaded compared
	  to the transfer time.  The slave might skip some intermediate
	  versions but the transfers will complete and it will keep
	  reasonably in sync with the master.
	</para>
	<para>
	  The new strategy also allows the master to recover from
	  syntax and other errors in the master file as it still
	  has an in-core copy of the old contents.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I want to use IPv6 locally but I don't have a external IPv6
	  connection.  External lookups are slow.
	</para>
      </question>
      <answer>
	<para>
	  You can use server clauses to stop named making external lookups
	  over IPv6.
	</para>
        <programlisting>
server fd81:ec6c:bd62::/48 { bogus no; }; // site ULA prefix
server ::/0 { bogus yes; };
</programlisting>
      </answer>
    </qandaentry>

    </qandadiv> <!-- Configuration and Setup Questions -->

    <qandadiv><title>Operations Questions</title>

    <qandaentry>
      <question>
	<para>
	  How to change the nameservers for a zone?
	</para>
      </question>
      <answer>
	<para>
	  Step 1: Ensure all nameservers, new and old, are serving the
	  same zone content.
	</para>
	<para>
	  Step 2: Work out the maximum TTL of the NS RRset in the parent and child
	  zones.  This is the time it will take caches to be clear of a
	  particular version of the NS RRset.
	  If you are just removing nameservers you can skip to Step 6.
	</para>
	<para>
	  Step 3: Add new nameservers to the NS RRset for the zone and
	  wait until all the servers for the zone are answering with this
	  new NS RRset.
	</para>
	<para>
	  Step 4: Inform the parent zone of the new NS RRset then wait for all the
	  parent servers to be answering with the new NS RRset.
	</para>
	<para>
	  Step 5: Wait for cache to be clear of the old NS RRset.
	  See Step 2 for how long.
	  If you are just adding nameservers you are done.
	</para>
	<para>
	  Step 6: Remove any old nameservers from the zones NS RRset and
	  wait for all the servers for the zone to be serving the new NS RRset.
	</para>
	<para>
	  Step 7: Inform the parent zone of the new NS RRset then wait for all the
	  parent servers to be answering with the new NS RRset.
	</para>
	<para>
	  Step 8: Wait for cache to be clear of the old NS RRset.
	  See Step 2 for how long.
	</para>
	<para>
	  Step 9: Turn off the old nameservers or remove the zone entry from
	  the configuration of the old nameservers.
	</para>
	<para>
	  Step 10: Increment the serial number and wait for the change to
	  be visible in all nameservers for the zone.  This ensures that
	  zone transfers are still working after the old servers are
	  decommissioned.
	</para>
	<para>
	  Note: the above procedure is designed to be transparent
	  to dns clients.  Decommissioning the old servers too early
	  will result in some clients not being able to look up
	  answers in the zone.
	</para>
	<para>
	  Note: while it is possible to run the addition and removal
	  stages together it is not recommended.
	</para>
      </answer>
    </qandaentry>

    </qandadiv> <!-- Operations Questions -->

    <qandadiv><title>General Questions</title>

    <qandaentry>
      <question>
	<para>
	  I keep getting log messages like the following.  Why?
	</para>
	<para>
	  Dec  4 23:47:59 client 10.0.0.1#1355: updating zone
	  'example.com/IN': update failed: 'RRset exists (value
	  dependent)' prerequisite not satisfied (NXRRSET)
	</para>
      </question>
      <answer>
	<para>
	  DNS updates allow the update request to test to see if
	  certain conditions are met prior to proceeding with the
	  update.  The message above is saying that conditions were
	  not met and the update is not proceeding.  See doc/rfc/rfc2136.txt
	  for more details on prerequisites.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I keep getting log messages like the following.  Why?
	</para>
	<para>
	  Jun 21 12:00:00.000 client 10.0.0.1#1234: update denied
	</para>
      </question>
      <answer>
	<para>
	  Someone is trying to update your DNS data using the RFC2136
	  Dynamic Update protocol.  Windows 2000 machines have a habit
	  of sending dynamic update requests to DNS servers without
	  being specifically configured to do so.  If the update
	  requests are coming from a Windows 2000 machine, see
	  <ulink
	   url="http://support.microsoft.com/support/kb/articles/q246/8/04.asp">
  &lt;http://support.microsoft.com/support/kb/articles/q246/8/04.asp&gt;</ulink>
	  for information about how to turn them off.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  When I do a "dig . ns", many of the A records for the root
	  servers are missing.  Why?
	</para>
      </question>
      <answer>
	<para>
	  This is normal and harmless.  It is a somewhat confusing
	  side effect of the way BIND 9 does RFC2181 trust ranking
	  and of the efforts BIND 9 makes to avoid promoting glue
	  into answers.
	</para>
	<para>
	 When BIND 9 first starts up and primes its cache, it receives
	 the root server addresses as additional data in an authoritative
	 response from a root server, and these records are eligible
	 for inclusion as additional data in responses.  Subsequently
	 it receives a subset of the root server addresses as
	 additional data in a non-authoritative (referral) response
	 from a root server.  This causes the addresses to now be
	 considered non-authoritative (glue) data, which is not
	 eligible for inclusion in responses.
	</para>
	<para>
	 The server does have a complete set of root server addresses
	 cached at all times, it just may not include all of them
	 as additional data, depending on whether they were last
	 received as answers or as glue.  You can always look up the
	 addresses with explicit queries like "dig a.root-servers.net A".
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Why don't my zones reload when I do an "rndc reload" or SIGHUP?
	</para>
      </question>
      <answer>
	<para>
	  A zone can be updated either by editing zone files and
	  reloading the server or by dynamic update, but not both.
	  If you have enabled dynamic update for a zone using the
	  "allow-update" option, you are not supposed to edit the
	  zone file by hand, and the server will not attempt to reload
	  it.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Why is named listening on UDP port other than 53?
	</para>
      </question>
      <answer>
	<para>
	  Named uses a system selected port to make queries of other
	  nameservers.  This behaviour can be overridden by using
	  query-source to lock down the port and/or address.  See
	  also notify-source and transfer-source.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I get warning messages like <quote>zone example.com/IN: refresh:
	  failure trying master 1.2.3.4#53: timed out</quote>.
	</para>
      </question>
      <answer>
	<para>
	Check that you can make UDP queries from the slave to the master
	</para>
	<informalexample>
	  <programlisting>
dig +norec example.com soa @1.2.3.4</programlisting>
	</informalexample>
	<para>
	  You could be generating queries faster than the slave can
	  cope with.  Lower the serial query rate.
	</para>
	<informalexample>
	  <programlisting>
serial-query-rate 5; // default 20</programlisting>
	</informalexample>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I don't get RRSIG's returned when I use "dig +dnssec".
	</para>
      </question>
      <answer>
	<para>
	  You need to ensure DNSSEC is enabled (dnssec-enable yes;).
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Can a NS record refer to a CNAME.
	</para>
      </question>
      <answer>
	<para>
	  No.  The rules for glue (copies of the *address* records
	  in the parent zones) and additional section processing do
	  not allow it to work.
	</para>
	<para>
	  You would have to add both the CNAME and address records
	  (A/AAAA) as glue to the parent zone and have CNAMEs be
	  followed when doing additional section processing to make
	  it work.  No nameserver implementation supports either of
	  these requirements.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  What does <quote>RFC 1918 response from Internet for
	  0.0.0.10.IN-ADDR.ARPA</quote> mean?
	</para>
      </question>
      <answer>
	<para>
	  If the IN-ADDR.ARPA name covered refers to a internal address
	  space you are using then you have failed to follow RFC 1918
	  usage rules and are leaking queries to the Internet.  You
	  should establish your own zones for these addresses to prevent
	  you querying the Internet's name servers for these addresses.
	  Please see <ulink url="http://as112.net/">&lt;http://as112.net/&gt;</ulink>
	  for details of the problems you are causing and the counter
	  measures that have had to be deployed.
	</para>
	<para>
	  If you are not using these private addresses then a client
	  has queried for them.  You can just ignore the messages,
	  get the offending client to stop sending you these messages
	  as they are most probably leaking them or setup your own zones
	  empty zones to serve answers to these queries.
	</para>
	<informalexample>
	  <programlisting>
zone "10.IN-ADDR.ARPA" {
	type master;
	file "empty";
};

zone "16.172.IN-ADDR.ARPA" {
	type master;
	file "empty";
};

...

zone "31.172.IN-ADDR.ARPA" {
	type master;
	file "empty";
};

zone "168.192.IN-ADDR.ARPA" {
	type master;
	file "empty";
};

empty:
@ 10800 IN SOA &lt;name-of-server&gt;. &lt;contact-email&gt;. (
	       1 3600 1200 604800 10800 )
@ 10800 IN NS &lt;name-of-server&gt;.</programlisting>
	</informalexample>
	<para>
	<note>
	  Future versions of named are likely to do this automatically.
	</note>
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Will named be affected by the 2007 changes to daylight savings
	  rules in the US.
	</para>
      </question>
      <answer>
	<para>
	  No, so long as the machines internal clock (as reported
	  by "date -u") remains at UTC.  The only visible change
	  if you fail to upgrade your OS, if you are in a affected
	  area, will be that log messages will be a hour out during
	  the period where the old rules do not match the new rules.
	</para>
	<para>
	  For most OS's this change just means that you need to
	  update the conversion rules from UTC to local time.
	  Normally this involves updating a file in /etc (which
	  sets the default timezone for the machine) and possibly
	  a directory which has all the conversion rules for the
	  world (e.g. /usr/share/zoneinfo).  When updating the OS
	  do not forget to update any chroot areas as well.
	  See your OS's documentation for more details.
	</para>
	<para>
	  The local timezone conversion rules can also be done on
	  a individual basis by setting the TZ environment variable
	  appropriately.  See your OS's documentation for more
	  details.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Is there a bugzilla (or other tool) database that mere
	  mortals can have (read-only) access to for bind?
	</para>
      </question>
      <answer>
	<para>
	  No.  The BIND 9 bug database is kept closed for a number
	  of reasons.  These include, but are not limited to, that
	  the database contains proprietory information from people
	  reporting bugs.  The database has in the past and may in
	  future contain unfixed bugs which are capable of bringing
	  down most of the Internet's DNS infrastructure.
	</para>
	<para>
	  The release pages for each version contain up to date
	  lists of bugs that have been fixed post release.  That
	  is as close as we can get to providing a bug database.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Why do queries for NSEC3 records fail to return the NSEC3 record?
	</para>
      </question>
      <answer>
	<para>
	  NSEC3 records are strictly meta data and can only be
	  returned in the authority section.  This is done so that
	  signing the zone using NSEC3 records does not bring names
	  into existence that do not exist in the unsigned version
	  of the zone.
	</para>
      </answer>
    </qandaentry>

    </qandadiv> <!-- General Questions -->

    <qandadiv><title>Operating-System Specific Questions</title>

    <qandadiv><title>HPUX</title>

    <qandaentry>
      <question>
	<para>I get the following error trying to configure BIND:
<programlisting>checking if unistd.h or sys/types.h defines fd_set... no
configure: error: need either working unistd.h or sys/select.h</programlisting>
	</para>
      </question>
      <answer>
	<para>
	  You have attempted to configure BIND with the bundled C compiler.
	  This compiler does not meet the minimum compiler requirements to
	  for building BIND.  You need to install a ANSI C compiler and / or
	  teach configure how to find the ANSI C compiler.  The later can
	  be done by adjusting the PATH environment variable and / or
	  specifying the compiler via CC.
	</para>
	<informalexample>
	  <programlisting>./configure CC=&lt;compiler&gt; ...</programlisting>
	</informalexample>
      </answer>
    </qandaentry>

    </qandadiv> <!-- HPUX -->

    <qandadiv><title>Linux</title>

    <qandaentry>
      <question>
	<para>
	  Why do I get the following errors:
<programlisting>general: errno2result.c:109: unexpected error:
general: unable to convert errno to isc_result: 14: Bad address
client: UDP client handler shutting down due to fatal receive error: unexpected error</programlisting>
	</para>
      </question>
      <answer>
	<para>
	  This is the result of a Linux kernel bug.
	</para>
	<para>
	  See:
	  <ulink url="http://marc.theaimsgroup.com/?l=linux-netdev&amp;m=113081708031466&amp;w=2">&lt;http://marc.theaimsgroup.com/?l=linux-netdev&amp;m=113081708031466&amp;w=2&gt;</ulink>
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Why does named lock up when it attempts to connect over IPSEC tunnels?
	</para>
      </question>
      <answer>
	<para>
	  This is due to a kernel bug where the fact that a socket is marked
	  non-blocking is ignored.  It is reported that setting
	  xfrm_larval_drop to 1 helps but this may have negative side effects.
	  See:
<ulink url="https://bugzilla.redhat.com/show_bug.cgi?id=427629">&lt;https://bugzilla.redhat.com/show_bug.cgi?id=427629&gt;</ulink>
	  and
<ulink url="http://lkml.org/lkml/2007/12/4/260">&lt;http://lkml.org/lkml/2007/12/4/260&gt;</ulink>.
	</para>
	<para>
	xfrm_larval_drop can be set to 1 by the following procedure:
<programlisting>
echo "1" &gt; proc/sys/net/core/xfrm_larval_drop</programlisting>
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Why do I see 5 (or more) copies of named on Linux?
	</para>
      </question>
      <answer>
	<para>
	  Linux threads each show up as a process under ps.  The
	  approximate number of threads running is n+4, where n is
	  the number of CPUs.  Note that the amount of memory used
	  is not cumulative; if each process is using 10M of memory,
	  only a total of 10M is used.
	</para>
	<para>
	  Newer versions of Linux's ps command hide the individual threads
	  and require -L to display them.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Why does BIND 9 log <quote>permission denied</quote> errors accessing
	  its configuration files or zones on my Linux system even
	  though it is running as root?
	</para>
      </question>
      <answer>
	<para>
	  On Linux, BIND 9 drops most of its root privileges on
	  startup.  This including the privilege to open files owned
	  by other users.  Therefore, if the server is running as
	  root, the configuration files and zone files should also
	  be owned by root.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I get the error message <quote>named: capset failed: Operation
	  not permitted</quote> when starting named.
	</para>
      </question>
      <answer>
	<para>
	  The capability module, part of "Linux Security Modules/LSM",
	  has not been loaded into the kernel.  See insmod(8), modprobe(8).
	</para>
	<para>
	  The relevant modules can be loaded by running:
<programlisting>
modprobe commoncap
modprobe capability</programlisting>
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	   I'm running BIND on Red Hat Enterprise Linux or Fedora Core -
	</para>
	<para>
	  Why can't named update slave zone database files?
	</para>
	<para>
	  Why can't named create DDNS journal files or update
	  the master zones from journals?
	</para>
	<para>
	  Why can't named create custom log files?
	</para>
      </question>

      <answer>
	<para>
	  Red Hat Security Enhanced Linux (SELinux) policy security
	  protections :
	</para>

	<para>
	   Red Hat have adopted the National Security Agency's
	   SELinux security policy (see <ulink
   url="http://www.nsa.gov/selinux">&lt;http://www.nsa.gov/selinux&gt;</ulink>)
	   and recommendations for BIND security , which are more
	   secure than running named in a chroot and make use of
	   the bind-chroot environment unnecessary .
	</para>

	<para>
	  By default, named is not allowed by the SELinux policy
	  to write, create or delete any files EXCEPT in these
	  directories:
	  <informalexample>
	    <programlisting>
$ROOTDIR/var/named/slaves
$ROOTDIR/var/named/data
$ROOTDIR/var/tmp
	    </programlisting>
	  </informalexample>
	  where $ROOTDIR may be set in /etc/sysconfig/named if
	  bind-chroot is installed.
	</para>

	<para>
	  The SELinux policy particularly does NOT allow named to modify
	  the $ROOTDIR/var/named directory, the default location for master
	  zone database files.
	</para>

	<para>
	  SELinux policy overrules file access permissions - so
	  even if all the files under /var/named have ownership
	  named:named and mode rw-rw-r--, named will still not be
	  able to write or create files except in the directories
	  above, with SELinux in Enforcing mode.
	</para>

	<para>
	  So, to allow named to update slave or DDNS zone files,
	  it is best to locate them in $ROOTDIR/var/named/slaves,
	  with named.conf zone statements such as:
	  <informalexample>
	    <programlisting>
zone "slave.zone." IN {
	type slave;
	file "slaves/slave.zone.db";
	...
};
zone "ddns.zone." IN  {
	type master;
	allow-updates {...};
	file "slaves/ddns.zone.db";
};
	    </programlisting>
	  </informalexample>
	</para>

	<para>
	  To allow named to create its cache dump and statistics
	  files, for example, you could use named.conf options
	  statements such as:
	  <informalexample>
	    <programlisting>
options {
	...
	dump-file "/var/named/data/cache_dump.db";
	statistics-file "/var/named/data/named_stats.txt";
	...
};
	    </programlisting>
	  </informalexample>
	</para>

	<para>
	  You can also tell SELinux to allow named to update any
	  zone database files, by setting the SELinux tunable boolean
	  parameter 'named_write_master_zones=1', using the
	  system-config-securitylevel GUI, using the 'setsebool'
	  command, or in /etc/selinux/targeted/booleans.
	</para>

	<para>
	  You can disable SELinux protection for named entirely by
	  setting the 'named_disable_trans=1' SELinux tunable boolean
	  parameter.
	</para>

	<para>
	  The SELinux named policy defines these SELinux contexts for named:
	  <informalexample>
	    <programlisting>
named_zone_t : for zone database files       - $ROOTDIR/var/named/*
named_conf_t : for named configuration files - $ROOTDIR/etc/{named,rndc}.*
named_cache_t: for files modifiable by named - $ROOTDIR/var/{tmp,named/{slaves,data}}
	    </programlisting>
	  </informalexample>
	</para>

	<para>
	  If you want to retain use of the SELinux policy for named,
	  and put named files in different locations, you can do
	  so by changing the context of the custom file locations
	  .
	</para>

	<para>
	  To create a custom configuration file location, e.g.
	  '/root/named.conf', to use with the 'named -c' option,
	  do:
	  <informalexample>
	    <programlisting>
# chcon system_u:object_r:named_conf_t /root/named.conf
	    </programlisting>
	  </informalexample>
	</para>

	<para>
	  To create a custom modifiable named data location, e.g.
	  '/var/log/named' for a log file, do:
	  <informalexample>
	    <programlisting>
# chcon system_u:object_r:named_cache_t /var/log/named
	    </programlisting>
	  </informalexample>
	</para>

	<para>
   To create a custom zone file location, e.g. /root/zones/, do:
	  <informalexample>
	    <programlisting>
# chcon system_u:object_r:named_zone_t /root/zones/{.,*}
	    </programlisting>
	  </informalexample>
	</para>

	<para>
	  See these man-pages for more information : selinux(8),
	  named_selinux(8), chcon(1), setsebool(8)
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	   I'm running BIND on Ubuntu -
	</para>
	<para>
	  Why can't named update slave zone database files?
	</para>
	<para>
	  Why can't named create DDNS journal files or update
	  the master zones from journals?
	</para>
	<para>
	  Why can't named create custom log files?
	</para>
      </question>
      <answer>
	<para>
	  Ubuntu uses AppArmor <ulink url="http://en.wikipedia.org/wiki/AppArmor">
          &lt;http://en.wikipedia.org/wiki/AppArmor&gt;</ulink> in
	  addition to normal file system permissions to protect the system.
	</para>
	<para>
	  Adjust the paths to use those specified in /etc/apparmor.d/usr.sbin.named
	  or adjust /etc/apparmor.d/usr.sbin.named to allow named to write at the
	  location specified in named.conf.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  Listening on individual IPv6 interfaces does not work.
	</para>
      </question>
      <answer>
	<para>
	  This is usually due to "/proc/net/if_inet6" not being available
	  in the chroot file system.  Mount another instance of "proc"
	  in the chroot file system.
	</para>
	<para>
	  This can be be made permanent by adding a second instance to
	  /etc/fstab.
	  <informalexample>
	    <programlisting>
proc /proc           proc defaults 0 0
proc /var/named/proc proc defaults 0 0</programlisting>
	  </informalexample>
	</para>
      </answer>
    </qandaentry>

    </qandadiv> <!-- Linux -->

    <qandadiv><title>Windows</title>

    <qandaentry>
      <question>
	<para>
	  Zone transfers from my BIND 9 master to my Windows 2000
	  slave fail.  Why?
	</para>
      </question>
      <answer>
	<para>
	  This may be caused by a bug in the Windows 2000 DNS server
	  where DNS messages larger than 16K are not handled properly.
	  This can be worked around by setting the option "transfer-format
	  one-answer;".  Also check whether your zone contains domain
	  names with embedded spaces or other special characters,
	  like "John\032Doe\213s\032Computer", since such names have
	  been known to cause Windows 2000 slaves to incorrectly
	  reject the zone.
	</para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question>
	<para>
	  I get <quote>Error 1067</quote> when starting named under Windows.
	</para>
      </question>
      <answer>
	<para>
	  This is the service manager saying that named exited.   You
	  need to examine the Application log in the EventViewer to
	  find out why.
	</para>
	<para>
	  Common causes are that you failed to create "named.conf"
	  (usually "C:\windows\dns\etc\named.conf") or failed to
	  specify the directory in named.conf.
	</para>
	<informalexample>
	  <programlisting>
options {
	Directory "C:\windows\dns\etc";
};</programlisting>
	</informalexample>
      </answer>
    </qandaentry>

    </qandadiv> <!-- Windows -->

    <qandadiv><title>FreeBSD</title>

    <qandaentry>
      <question>
	<para>
	  I have FreeBSD 4.x and "rndc-confgen -a" just sits there.
	</para>
      </question>
      <answer>
	<para>
	  /dev/random is not configured.  Use rndcontrol(8) to tell
	  the kernel to use certain interrupts as a source of random
	  events.  You can make this permanent by setting rand_irqs
	  in /etc/rc.conf.
	</para>
	<informalexample>
	  <programlisting>
rand_irqs="3 14 15"</programlisting>
	</informalexample>
	<para>
	  See also
	  <ulink url="http://people.freebsd.org/~dougb/randomness.html">
	  &lt;http://people.freebsd.org/~dougb/randomness.html&gt;</ulink>.
	</para>
      </answer>
    </qandaentry>

    </qandadiv> <!-- FreeBSD -->

    <qandadiv><title>Solaris</title>

    <qandaentry>
      <question>
	<para>
	  How do I integrate BIND 9 and Solaris SMF
	</para>
      </question>
      <answer>
	<para>
	  Sun has a blog entry describing how to do this.
	</para>
	<para>
	  <ulink
	  url="http://blogs.sun.com/roller/page/anay/Weblog?catname=%2FSolaris">
	 &lt;http://blogs.sun.com/roller/page/anay/Weblog?catname=%2FSolaris&gt;
	  </ulink>
	</para>
      </answer>
    </qandaentry>

    </qandadiv>

    <qandadiv><title>Apple Mac OS X</title>

    <qandaentry>
      <question>
	<para>
	  How do I run BIND 9 on Apple Mac OS X?
	</para>
      </question>
      <answer>
	<para>
	 If you run Tiger(Mac OS 10.4) or later then this is all you need to do:
	</para>
	<informalexample>
	  <programlisting>
% sudo rndc-confgen  > /etc/rndc.conf</programlisting>
	</informalexample>
	<para>
	  Copy the key statement from /etc/rndc.conf into /etc/rndc.key, e.g.:
	</para>
	<informalexample>
	  <programlisting>
key "rndc-key" {
	algorithm hmac-sha256;
	secret "uvceheVuqf17ZwIcTydddw==";
};</programlisting>
	</informalexample>
	<para>
	  Then start the relevant service:
	</para>
	<informalexample>
	  <programlisting>
% sudo service org.isc.named start</programlisting>
	</informalexample>
	<para>
	  This is persistent upon a reboot, so you will have to do it only once.
	</para>
      </answer>

      <answer>
	<para>
	 Alternatively you can just generate /etc/rndc.key by running:
	</para>
	<informalexample>
	  <programlisting>
% sudo rndc-confgen -a</programlisting>
	</informalexample>
	<para>
	  Then start the relevant service:
	</para>
	<informalexample>
	  <programlisting>
% sudo service org.isc.named start</programlisting>
	</informalexample>
	<para>
	  Named will look for /etc/rndc.key when it starts if it
	  doesn't have a controls section or the existing controls are
	  missing keys sub-clauses.  This is persistent upon a
	  reboot, so you will have to do it only once.
	</para>
      </answer>
    </qandaentry>

    </qandadiv>

    </qandadiv> <!-- Operating-System Specific Questions -->

  </qandaset>
</article>