1 Frequently Asked Questions about BIND 9
3 Copyright © 2004-2008 Internet Systems Consortium, Inc. ("ISC")
5 Copyright © 2000-2003 Internet Software Consortium.
7 -----------------------------------------------------------------------
9 1. Compilation and Installation Questions
11 Q: I'm trying to compile BIND 9, and "make" is failing due to files not
14 A: Using a parallel or distributed "make" to build BIND 9 is not
15 supported, and doesn't work. If you are using one of these, use normal
16 make or gmake instead.
18 Q: Isn't "make install" supposed to generate a default named.conf?
22 Long Answer: There really isn't a default configuration which fits any
23 site perfectly. There are lots of decisions that need to be made and
24 there is no consensus on what the defaults should be. For example
25 FreeBSD uses /etc/namedb as the location where the configuration files
26 for named are stored. Others use /var/named.
28 What addresses to listen on? For a laptop on the move a lot you may
29 only want to listen on the loop back interfaces.
31 Who do you offer recursive service to? Is there are firewall to
32 consider? If so is it stateless or stateful. Are you directly on the
33 Internet? Are you on a private network? Are you on a NAT'd network? The
34 answers to all these questions change how you configure even a caching
37 2. Configuration and Setup Questions
39 Q: Why does named log the warning message "no TTL specified - using SOA
42 A: Your zone file is illegal according to RFC1035. It must either have a
47 at the beginning, or the first record in it must have a TTL field, like
48 the "84600" in this example:
50 example.com. 86400 IN SOA ns hostmaster ( 1 3600 1800 1814400 3600 )
52 Q: Why do I get errors like "dns_zone_load: zone foo/IN: loading master
53 file bar: ran out of space"?
55 A: This is often caused by TXT records with missing close quotes. Check
56 that all TXT records containing quoted strings have both open and close
59 Q: How do I restrict people from looking up the server version?
61 A: Put a "version" option containing something other than the real version
62 in the "options" section of named.conf. Note doing this will not
63 prevent attacks and may impede people trying to diagnose problems with
64 your server. Also it is possible to "fingerprint" nameservers to
65 determine their version.
67 Q: How do I restrict only remote users from looking up the server version?
69 A: The following view statement will intercept lookups as the internal
70 view that holds the version information will be matched last. The
71 caveats of the previous answer still apply, of course.
74 match-clients { <those to be refused>; };
75 allow-query { none; };
78 file "/dev/null"; // or any empty file
82 Q: What do "no source of entropy found" or "could not open entropy source
85 A: The server requires a source of entropy to perform certain operations,
86 mostly DNSSEC related. These messages indicate that you have no source
87 of entropy. On systems with /dev/random or an equivalent, it is used by
88 default. A source of entropy can also be defined using the
89 random-device option in named.conf.
91 Q: I'm trying to use TSIG to authenticate dynamic updates or zone
92 transfers. I'm sure I have the keys set up correctly, but the server is
93 rejecting the TSIG. Why?
95 A: This may be a clock skew problem. Check that the the clocks on the
96 client and server are properly synchronised (e.g., using ntp).
98 Q: I see a log message like the following. Why?
100 couldn't open pid file '/var/run/named.pid': Permission denied
102 A: You are most likely running named as a non-root user, and that user
103 does not have permission to write in /var/run. The common ways of
104 fixing this are to create a /var/run/named directory owned by the named
105 user and set pid-file to "/var/run/named/named.pid", or set pid-file to
106 "named.pid", which will put the file in the directory specified by the
107 directory option (which, in this case, must be writable by the named
110 Q: I can query the nameserver from the nameserver but not from other
113 A: This is usually the result of the firewall configuration stopping the
114 queries and / or the replies.
116 Q: How can I make a server a slave for both an internal and an external
117 view at the same time? When I tried, both views on the slave were
118 transferred from the same view on the master.
120 A: You will need to give the master and slave multiple IP addresses and
121 use those to make sure you reach the correct view on the other machine.
123 Master: 10.0.1.1 (internal), 10.0.1.2 (external, IP alias)
125 match-clients { !10.0.1.2; !10.0.1.4; 10.0.1/24; };
126 notify-source 10.0.1.1;
127 transfer-source 10.0.1.1;
128 query-source address 10.0.1.1;
130 match-clients { any; };
131 recursion no; // don't offer recursion to the world
132 notify-source 10.0.1.2;
133 transfer-source 10.0.1.2;
134 query-source address 10.0.1.2;
136 Slave: 10.0.1.3 (internal), 10.0.1.4 (external, IP alias)
138 match-clients { !10.0.1.2; !10.0.1.4; 10.0.1/24; };
139 notify-source 10.0.1.3;
140 transfer-source 10.0.1.3;
141 query-source address 10.0.1.3;
143 match-clients { any; };
144 recursion no; // don't offer recursion to the world
145 notify-source 10.0.1.4;
146 transfer-source 10.0.1.4;
147 query-source address 10.0.1.4;
149 You put the external address on the alias so that all the other dns
150 clients on these boxes see the internal view by default.
152 A: BIND 9.3 and later: Use TSIG to select the appropriate view.
160 match-clients { !key external; 10.0.1/24; };
164 match-clients { key external; any; };
165 server 10.0.1.2 { keys external; };
176 match-clients { !key external; 10.0.1/24; };
180 match-clients { key external; any; };
181 server 10.0.1.1 { keys external; };
186 Q: I get error messages like "multiple RRs of singleton type" and "CNAME
187 and other data" when transferring a zone. What does this mean?
189 A: These indicate a malformed master zone. You can identify the exact
190 records involved by transferring the zone using dig then running
191 named-checkzone on it.
193 dig axfr example.com @master-server > tmp
194 named-checkzone example.com tmp
196 A CNAME record cannot exist with the same name as another record except
197 for the DNSSEC records which prove its existence (NSEC).
199 RFC 1034, Section 3.6.2: "If a CNAME RR is present at a node, no other
200 data should be present; this ensures that the data for a canonical name
201 and its aliases cannot be different. This rule also insures that a
202 cached CNAME can be used without checking with an authoritative server
205 Q: I get error messages like "named.conf:99: unexpected end of input"
206 where 99 is the last line of named.conf.
208 A: Some text editors (notepad and wordpad) fail to put a line title
209 indication (e.g. CR/LF) on the last line of a text file. This can be
210 fixed by "adding" a blank line to the end of the file. Named expects to
211 see EOF immediately after EOL and treats text files where this is not
214 Q: How do I share a dynamic zone between multiple views?
216 A: You choose one view to be master and the second a slave and transfer
217 the zone between views.
231 match-clients { !key external; 10.0.1/24; };
233 /* Deliver notify messages to external view. */
238 file "internal/example.db";
239 allow-update { key mykey; };
240 notify-also { 10.0.1.1; };
245 match-clients { key external; any; };
248 file "external/example.db";
249 masters { 10.0.1.1; };
250 transfer-source { 10.0.1.1; };
251 // allow-update-forwarding { any; };
252 // allow-notify { ... };
256 Q: I get a error message like "zone wireless.ietf56.ietf.org/IN: loading
257 master file primaries/wireless.ietf56.ietf.org: no owner".
259 A: This error is produced when a line in the master file contains leading
260 white space (tab/space) but the is no current record owner name to
261 inherit the name from. Usually this is the result of putting white
262 space before a comment, forgetting the "@" for the SOA record, or
263 indenting the master file.
265 Q: Why are my logs in GMT (UTC).
267 A: You are running chrooted (-t) and have not supplied local timezone
268 information in the chroot area.
270 FreeBSD: /etc/localtime
271 Solaris: /etc/TIMEZONE and /usr/share/lib/zoneinfo
272 OSF: /etc/zoneinfo/localtime
274 See also tzset(3) and zic(8).
276 Q: I get "rndc: connect failed: connection refused" when I try to run
279 A: This is usually a configuration error.
281 First ensure that named is running and no errors are being reported at
282 startup (/var/log/messages or equivalent). Running "named -g <usual
283 arguments>" from a title can help at this point.
285 Secondly ensure that named is configured to use rndc either by
286 "rndc-confgen -a", rndc-confgen or manually. The Administrators
287 Reference manual has details on how to do this.
289 Old versions of rndc-confgen used localhost rather than 127.0.0.1 in /
290 etc/rndc.conf for the default server. Update /etc/rndc.conf if
291 necessary so that the default server listed in /etc/rndc.conf matches
292 the addresses used in named.conf. "localhost" has two address
295 If you use "rndc-confgen -a" and named is running with -t or -u ensure
296 that /etc/rndc.conf has the correct ownership and that a copy is in the
297 chroot area. You can do this by re-running "rndc-confgen -a" with
298 appropriate -t and -u arguments.
300 Q: I get "transfer of 'example.net/IN' from 192.168.4.12#53: failed while
301 receiving responses: permission denied" error messages.
303 A: These indicate a filesystem permission error preventing named creating
304 / renaming the temporary file. These will usually also have other
305 associated error messages like
307 "dumping master file: sl/tmp-XXXX5il3sQ: open: permission denied"
309 Named needs write permission on the directory containing the file.
310 Named writes the new cache file to a temporary file then renames it to
311 the name specified in named.conf to ensure that the contents are always
312 complete. This is to prevent named loading a partial zone in the event
313 of power failure or similar interrupting the write of the master file.
315 Note file names are relative to the directory specified in options and
316 any chroot directory ([<chroot dir>/][<options dir>]).
318 If named is invoked as "named -t /chroot/DNS" with the following
319 named.conf then "/chroot/DNS/var/named/sl" needs to be writable by the
320 user named is running as.
323 directory "/var/named";
328 file "sl/example.net";
329 masters { 192.168.4.12; };
332 Q: I want to forward all DNS queries from my caching nameserver to another
333 server. But there are some domains which have to be served locally, via
336 How do I achieve this ?
340 forwarders { <ip.of.primary.nameserver>; };
343 zone "sbl-xbl.spamhaus.org" {
344 type forward; forward only;
345 forwarders { <ip.of.rbldns.server> port 530; };
348 zone "list.dsbl.org" {
349 type forward; forward only;
350 forwarders { <ip.of.rbldns.server> port 530; };
354 Q: Can you help me understand how BIND 9 uses memory to store DNS zones?
356 Some times it seems to take several times the amount of memory it needs
359 A: When reloading a zone named my have multiple copies of the zone in
360 memory at one time. The zone it is serving and the one it is loading.
361 If reloads are ultra fast it can have more still.
363 e.g. Ones that are transferring out, the one that it is serving and the
366 BIND 8 destroyed the zone before loading and also killed off outgoing
367 transfers of the zone.
369 The new strategy allows slaves to get copies of the new zone regardless
370 of how often the master is loaded compared to the transfer time. The
371 slave might skip some intermediate versions but the transfers will
372 complete and it will keep reasonably in sync with the master.
374 The new strategy also allows the master to recover from syntax and
375 other errors in the master file as it still has an in-core copy of the
380 Q: I keep getting log messages like the following. Why?
382 Dec 4 23:47:59 client 10.0.0.1#1355: updating zone 'example.com/IN':
383 update failed: 'RRset exists (value dependent)' prerequisite not
386 A: DNS updates allow the update request to test to see if certain
387 conditions are met prior to proceeding with the update. The message
388 above is saying that conditions were not met and the update is not
389 proceeding. See doc/rfc/rfc2136.txt for more details on prerequisites.
391 Q: I keep getting log messages like the following. Why?
393 Jun 21 12:00:00.000 client 10.0.0.1#1234: update denied
395 A: Someone is trying to update your DNS data using the RFC2136 Dynamic
396 Update protocol. Windows 2000 machines have a habit of sending dynamic
397 update requests to DNS servers without being specifically configured to
398 do so. If the update requests are coming from a Windows 2000 machine,
399 see http://support.microsoft.com/support/kb/articles/q246/8/04.asp for
400 information about how to turn them off.
402 Q: When I do a "dig . ns", many of the A records for the root servers are
405 A: This is normal and harmless. It is a somewhat confusing side effect of
406 the way BIND 9 does RFC2181 trust ranking and of the efforts BIND 9
407 makes to avoid promoting glue into answers.
409 When BIND 9 first starts up and primes its cache, it receives the root
410 server addresses as additional data in an authoritative response from a
411 root server, and these records are eligible for inclusion as additional
412 data in responses. Subsequently it receives a subset of the root server
413 addresses as additional data in a non-authoritative (referral) response
414 from a root server. This causes the addresses to now be considered
415 non-authoritative (glue) data, which is not eligible for inclusion in
418 The server does have a complete set of root server addresses cached at
419 all times, it just may not include all of them as additional data,
420 depending on whether they were last received as answers or as glue. You
421 can always look up the addresses with explicit queries like "dig
422 a.root-servers.net A".
424 Q: Why don't my zones reload when I do an "rndc reload" or SIGHUP?
426 A: A zone can be updated either by editing zone files and reloading the
427 server or by dynamic update, but not both. If you have enabled dynamic
428 update for a zone using the "allow-update" option, you are not supposed
429 to edit the zone file by hand, and the server will not attempt to
432 Q: Why is named listening on UDP port other than 53?
434 A: Named uses a system selected port to make queries of other nameservers.
435 This behaviour can be overridden by using query-source to lock down the
436 port and/or address. See also notify-source and transfer-source.
438 Q: I get warning messages like "zone example.com/IN: refresh: failure
439 trying master 1.2.3.4#53: timed out".
441 A: Check that you can make UDP queries from the slave to the master
443 dig +norec example.com soa @1.2.3.4
445 You could be generating queries faster than the slave can cope with.
446 Lower the serial query rate.
448 serial-query-rate 5; // default 20
450 Q: I don't get RRSIG's returned when I use "dig +dnssec".
452 A: You need to ensure DNSSEC is enabled (dnssec-enable yes;).
454 Q: Can a NS record refer to a CNAME.
456 A: No. The rules for glue (copies of the *address* records in the parent
457 zones) and additional section processing do not allow it to work.
459 You would have to add both the CNAME and address records (A/AAAA) as
460 glue to the parent zone and have CNAMEs be followed when doing
461 additional section processing to make it work. No nameserver
462 implementation supports either of these requirements.
464 Q: What does "RFC 1918 response from Internet for 0.0.0.10.IN-ADDR.ARPA"
467 A: If the IN-ADDR.ARPA name covered refers to a internal address space you
468 are using then you have failed to follow RFC 1918 usage rules and are
469 leaking queries to the Internet. You should establish your own zones
470 for these addresses to prevent you querying the Internet's name servers
471 for these addresses. Please see http://as112.net/ for details of the
472 problems you are causing and the counter measures that have had to be
475 If you are not using these private addresses then a client has queried
476 for them. You can just ignore the messages, get the offending client to
477 stop sending you these messages as they are most probably leaking them
478 or setup your own zones empty zones to serve answers to these queries.
480 zone "10.IN-ADDR.ARPA" {
485 zone "16.172.IN-ADDR.ARPA" {
492 zone "31.172.IN-ADDR.ARPA" {
497 zone "168.192.IN-ADDR.ARPA" {
503 @ 10800 IN SOA <name-of-server>. <contact-email>. (
504 1 3600 1200 604800 10800 )
505 @ 10800 IN NS <name-of-server>.
509 Future versions of named are likely to do this automatically.
511 Q: Will named be affected by the 2007 changes to daylight savings rules in
514 A: No, so long as the machines internal clock (as reported by "date -u")
515 remains at UTC. The only visible change if you fail to upgrade your OS,
516 if you are in a affected area, will be that log messages will be a hour
517 out during the period where the old rules do not match the new rules.
519 For most OS's this change just means that you need to update the
520 conversion rules from UTC to local time. Normally this involves
521 updating a file in /etc (which sets the default timezone for the
522 machine) and possibly a directory which has all the conversion rules
523 for the world (e.g. /usr/share/zoneinfo). When updating the OS do not
524 forget to update any chroot areas as well. See your OS's documentation
527 The local timezone conversion rules can also be done on a individual
528 basis by setting the TZ environment variable appropriately. See your
529 OS's documentation for more details.
531 Q: Is there a bugzilla (or other tool) database that mere mortals can have
532 (read-only) access to for bind?
534 A: No. The BIND 9 bug database is kept closed for a number of reasons.
535 These include, but are not limited to, that the database contains
536 proprietory information from people reporting bugs. The database has in
537 the past and may in future contain unfixed bugs which are capable of
538 bringing down most of the Internet's DNS infrastructure.
540 The release pages for each version contain up to date lists of bugs
541 that have been fixed post release. That is as close as we can get to
542 providing a bug database.
544 4. Operating-System Specific Questions
548 Q: I get the following error trying to configure BIND:
550 checking if unistd.h or sys/types.h defines fd_set... no
551 configure: error: need either working unistd.h or sys/select.h
553 A: You have attempted to configure BIND with the bundled C compiler. This
554 compiler does not meet the minimum compiler requirements to for
555 building BIND. You need to install a ANSI C compiler and / or teach
556 configure how to find the ANSI C compiler. The later can be done by
557 adjusting the PATH environment variable and / or specifying the
560 ./configure CC=<compiler> ...
564 Q: Why do I get the following errors:
566 general: errno2result.c:109: unexpected error:
567 general: unable to convert errno to isc_result: 14: Bad address
568 client: UDP client handler shutting down due to fatal receive error: unexpected error
570 A: This is the result of a Linux kernel bug.
572 See: http://marc.theaimsgroup.com/?l=linux-netdev&m=113081708031466&w=2
574 Q: Why do I see 5 (or more) copies of named on Linux?
576 A: Linux threads each show up as a process under ps. The approximate
577 number of threads running is n+4, where n is the number of CPUs. Note
578 that the amount of memory used is not cumulative; if each process is
579 using 10M of memory, only a total of 10M is used.
581 Newer versions of Linux's ps command hide the individual threads and
582 require -L to display them.
584 Q: Why does BIND 9 log "permission denied" errors accessing its
585 configuration files or zones on my Linux system even though it is
588 A: On Linux, BIND 9 drops most of its root privileges on startup. This
589 including the privilege to open files owned by other users. Therefore,
590 if the server is running as root, the configuration files and zone
591 files should also be owned by root.
593 Q: I get the error message "named: capset failed: Operation not permitted"
596 A: The capability module, part of "Linux Security Modules/LSM", has not
597 been loaded into the kernel. See insmod(8), modprobe(8).
599 The relevant modules can be loaded by running:
604 Q: I'm running BIND on Red Hat Enterprise Linux or Fedora Core -
606 Why can't named update slave zone database files?
608 Why can't named create DDNS journal files or update the master zones
611 Why can't named create custom log files?
613 A: Red Hat Security Enhanced Linux (SELinux) policy security protections :
615 Red Hat have adopted the National Security Agency's SELinux security
616 policy ( see http://www.nsa.gov/selinux ) and recommendations for BIND
617 security , which are more secure than running named in a chroot and
618 make use of the bind-chroot environment unnecessary .
620 By default, named is not allowed by the SELinux policy to write, create
621 or delete any files EXCEPT in these directories:
623 $ROOTDIR/var/named/slaves
624 $ROOTDIR/var/named/data
628 where $ROOTDIR may be set in /etc/sysconfig/named if bind-chroot is
631 The SELinux policy particularly does NOT allow named to modify the
632 $ROOTDIR/var/named directory, the default location for master zone
635 SELinux policy overrules file access permissions - so even if all the
636 files under /var/named have ownership named:named and mode rw-rw-r--,
637 named will still not be able to write or create files except in the
638 directories above, with SELinux in Enforcing mode.
640 So, to allow named to update slave or DDNS zone files, it is best to
641 locate them in $ROOTDIR/var/named/slaves, with named.conf zone
644 zone "slave.zone." IN {
646 file "slaves/slave.zone.db";
649 zone "ddns.zone." IN {
652 file "slaves/ddns.zone.db";
656 To allow named to create its cache dump and statistics files, for
657 example, you could use named.conf options statements such as:
661 dump-file "/var/named/data/cache_dump.db";
662 statistics-file "/var/named/data/named_stats.txt";
667 You can also tell SELinux to allow named to update any zone database
668 files, by setting the SELinux tunable boolean parameter
669 'named_write_master_zones=1', using the system-config-securitylevel
670 GUI, using the 'setsebool' command, or in /etc/selinux/targeted/
673 You can disable SELinux protection for named entirely by setting the
674 'named_disable_trans=1' SELinux tunable boolean parameter.
676 The SELinux named policy defines these SELinux contexts for named:
678 named_zone_t : for zone database files - $ROOTDIR/var/named/*
679 named_conf_t : for named configuration files - $ROOTDIR/etc/{named,rndc}.*
680 named_cache_t: for files modifiable by named - $ROOTDIR/var/{tmp,named/{slaves,data}}
683 If you want to retain use of the SELinux policy for named, and put
684 named files in different locations, you can do so by changing the
685 context of the custom file locations .
687 To create a custom configuration file location, e.g. '/root/
688 named.conf', to use with the 'named -c' option, do:
690 # chcon system_u:object_r:named_conf_t /root/named.conf
693 To create a custom modifiable named data location, e.g. '/var/log/
694 named' for a log file, do:
696 # chcon system_u:object_r:named_cache_t /var/log/named
699 To create a custom zone file location, e.g. /root/zones/, do:
701 # chcon system_u:object_r:named_zone_t /root/zones/{.,*}
704 See these man-pages for more information : selinux(8), named_selinux
705 (8), chcon(1), setsebool(8)
707 Q: Listening on individual IPv6 interfaces does not work.
709 A: This is usually due to "/proc/net/if_inet6" not being available in the
710 chroot file system. Mount another instance of "proc" in the chroot file
713 This can be be made permanent by adding a second instance to /etc/
716 proc /proc proc defaults 0 0
717 proc /var/named/proc proc defaults 0 0
721 Q: Zone transfers from my BIND 9 master to my Windows 2000 slave fail.
724 A: This may be caused by a bug in the Windows 2000 DNS server where DNS
725 messages larger than 16K are not handled properly. This can be worked
726 around by setting the option "transfer-format one-answer;". Also check
727 whether your zone contains domain names with embedded spaces or other
728 special characters, like "John\032Doe\213s\032Computer", since such
729 names have been known to cause Windows 2000 slaves to incorrectly
732 Q: I get "Error 1067" when starting named under Windows.
734 A: This is the service manager saying that named exited. You need to
735 examine the Application log in the EventViewer to find out why.
737 Common causes are that you failed to create "named.conf" (usually "C:\
738 windows\dns\etc\named.conf") or failed to specify the directory in
742 Directory "C:\windows\dns\etc";
747 Q: I have FreeBSD 4.x and "rndc-confgen -a" just sits there.
749 A: /dev/random is not configured. Use rndcontrol(8) to tell the kernel to
750 use certain interrupts as a source of random events. You can make this
751 permanent by setting rand_irqs in /etc/rc.conf.
756 See also http://people.freebsd.org/~dougb/randomness.html
760 Q: How do I integrate BIND 9 and Solaris SMF
762 A: Sun has a blog entry describing how to do this.
764 http://blogs.sun.com/roller/page/anay/Weblog?catname=%2FSolaris
768 Q: How do I run BIND 9 on Apple Mac OS X?
770 A: If you run Tiger(Mac OS 10.4) or later then this is all you need to do:
772 % sudo rndc-confgen > /etc/rndc.conf
774 Copy the key statement from /etc/rndc.conf into /etc/rndc.key, e.g.:
778 secret "uvceheVuqf17ZwIcTydddw==";
781 Then start the relevant service:
783 % sudo service org.isc.named start
785 This is persistent upon a reboot, so you will have to do it only once.
787 A: Alternatively you can just generate /etc/rndc.key by running:
789 % sudo rndc-confgen -a
791 Then start the relevant service:
793 % sudo service org.isc.named start
795 Named will look for /etc/rndc.key when it starts if it doesn't have a
796 controls section or the existing controls are missing keys sub-clauses.
797 This is persistent upon a reboot, so you will have to do it only once.
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