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@@ -1,721 +1,417 @@ -Frequently Asked Questions about BIND 9 - -Copyright © 2004-2007 Internet Systems Consortium, Inc. ("ISC") -Copyright © 2000-2003 Internet Software Consortium. -------------------------------------------------------------------------------- - -Q: Why doesn't -u work on Linux 2.2.x when I build with --enable-threads? -A: Linux threads do not fully implement the Posix threads (pthreads) standard. In - particular, setuid() operates only on the current thread, not the full process. - Because of this limitation, BIND 9 cannot use setuid() on Linux as it can on - all other supported platforms. setuid() cannot be called before creating - threads, since the server does not start listening on reserved ports until - after threads have started. +Frequently Asked Questions about BIND 9 - In the 2.2.18 or 2.3.99-pre3 and newer kernels, the ability to preserve - capabilities across a setuid() call is present. This allows BIND 9 to call - setuid() early, while retaining the ability to bind reserved ports. This is a - Linux-specific hack. - On a 2.2 kernel, BIND 9 does drop many root privileges, so it should be less of - a security risk than a root process that has not dropped privileges. +Q: Why doesn't -u work on Linux 2.2.x when I build with --enable-threads? - If Linux threads ever work correctly, this restriction will go away. +A: Linux threads do not fully implement the Posix threads (pthreads) standard. +In particular, setuid() operates only on the current thread, not the full +process. Because of this limitation, BIND 9 cannot use setuid() on Linux as it +can on all other supported platforms. setuid() cannot be called before +creating threads, since the server does not start listening on reserved ports +until after threads have started. - Configuring BIND9 with the --disable-threads option (the default) causes a - non-threaded version to be built, which will allow -u to be used. + In the 2.2.18 or 2.3.99-pre3 and newer kernels, the ability to preserve +capabilities across a setuid() call is present. This allows BIND 9 to call +setuid() early, while retaining the ability to bind reserved ports. This is +a Linux-specific hack. -Q: Why do I get the following errors: + On a 2.2 kernel, BIND 9 does drop many root privileges, so it should be less +of a security risk than a root process that has not dropped privileges. - 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 + If Linux threads ever work correctly, this restriction will go away. -A: This is the result of a Linux kernel bug. + Configuring BIND9 with the --disable-threads option (the default) causes a +non-threaded version to be built, which will allow -u to be used. - See: http://marc.theaimsgroup.com/?l=linux-netdev&m=113081708031466&w=2 -Q: Why does named log the warning message "no TTL specified - using SOA MINTTL - instead"? +Q: Why does named log the warning message "no TTL specified - using SOA +MINTTL instead"? -A: Your zone file is illegal according to RFC1035. It must either have a line - like: +A: Your zone file is illegal according to RFC1035. It must either +have a line like $TTL 86400 - at the beginning, or the first record in it must have a TTL field, like the - "84600" in this example: +at the beginning, or the first record in it must have a TTL field, +like the "84600" in this example: example.com. 86400 IN SOA ns hostmaster ( 1 3600 1800 1814400 3600 ) Q: Why do I see 5 (or more) copies of named on Linux? -A: 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. - - Newer versions of Linux's ps command hide the individual threads and require -L - to display them. - -Q: Why does BIND 9 log "permission denied" errors accessing its configuration - files or zones on my Linux system even though it is running as root? - -A: 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. - -Q: Why do I get errors like "dns_zone_load: zone foo/IN: loading master file bar: - ran out of space"? - -A: 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. - -Q: How do I produce a usable core file from a multi-threaded named on Linux? - -A: If the Linux kernel is 2.4.7 or newer, multi-threaded core dumps are usable - (that is, the correct thread is dumped). Otherwise, if using a 2.2 kernel, - apply the kernel patch found in contrib/linux/coredump-patch and rebuild the - kernel. This patch will cause multi-threaded programs to dump the correct - thread. - -Q: How do I restrict people from looking up the server version? - -A: 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. - -Q: How do I restrict only remote users from looking up the server version? - -A: 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. - - view "chaos" chaos { - match-clients { <those to be refused>; }; - allow-query { none; }; - zone "." { - type hint; - file "/dev/null"; // or any empty file - }; - }; - -Q: What do "no source of entropy found" or "could not open entropy source foo" - mean? - -A: 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. - -Q: I installed BIND 9 and restarted named, but it's still BIND 8. Why? - -A: BIND 9 is installed under /usr/local by default. BIND 8 is often installed - under /usr. Check that the correct named is running. - -Q: 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? +A: 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. -A: This may be a clock skew problem. Check that the the clocks on the client and - server are properly synchronised (e.g., using ntp). -Q: I'm trying to compile BIND 9, and "make" is failing due to files not being - found. Why? +Q: Why does BIND 9 log "permission denied" errors accessing its +configuration files or zones on my Linux system even though it is running +as root? -A: 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. +A: 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. -Q: I have a BIND 9 master and a BIND 8.2.3 slave, and the master is logging error - messages like "notify to 10.0.0.1#53 failed: unexpected end of input". What's - wrong? -A: This error message is caused by a known bug in BIND 8.2.3 and is fixed in BIND - 8.2.4. It can be safely ignored - the notify has been acted on by the slave - despite the error message. +Q: Why do I get errors like "dns_zone_load: zone foo/IN: loading master file +bar: ran out of space" -Q: I keep getting log messages like the following. Why? +A: 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. - 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) - -A: 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. - -Q: I keep getting log messages like the following. Why? - - Jun 21 12:00:00.000 client 10.0.0.1#1234: update denied - -A: 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 http:// - support.microsoft.com/support/kb/articles/q246/8/04.asp for information about - how to turn them off. - -Q: I see a log message like the following. Why? - - couldn't open pid file '/var/run/named.pid': Permission denied - -A: 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 named user). - -Q: When I do a "dig . ns", many of the A records for the root servers are missing. - Why? - -A: 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. - - 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. - - 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". - -Q: Zone transfers from my BIND 9 master to my Windows 2000 slave fail. Why? - -A: 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. - -Q: Why don't my zones reload when I do an "rndc reload" or SIGHUP? - -A: 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. - -Q: I can query the nameserver from the nameserver but not from other machines. - Why? - -A: This is usually the result of the firewall configuration stopping the queries - and / or the replies. - -Q: 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. - -A: 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. - - 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; - - You put the external address on the alias so that all the other dns clients on - these boxes see the internal view by default. - -A: BIND 9.3 and later: Use TSIG to select the appropriate view. - - Master 10.0.1.1: - key "external" { - algorithm hmac-md5; - secret "xxxxxxxx"; - }; - view "internal" { - match-clients { !key external; 10.0.1/24; }; - ... - }; - view "external" { - match-clients { key external; any; }; - server 10.0.1.2 { keys external; }; - recursion no; - ... - }; - - Slave 10.0.1.2: - key "external" { - algorithm hmac-md5; - secret "xxxxxxxx"; - }; - 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; - ... - }; - -Q: I have FreeBSD 4.x and "rndc-confgen -a" just sits there. - -A: /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. - - /etc/rc.conf - rand_irqs="3 14 15" - - See also http://people.freebsd.org/~dougb/randomness.html - -Q: Why is named listening on UDP port other than 53? - -A: 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. - -Q: I get error messages like "multiple RRs of singleton type" and "CNAME and other - data" when transferring a zone. What does this mean? - -A: 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. - - dig axfr example.com @master-server > tmp - named-checkzone example.com tmp - - A CNAME record cannot exist with the same name as another record except for the - DNSSEC records which prove its existence (NSEC). - - RFC 1034, Section 3.6.2: "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." - -Q: I get error messages like "named.conf:99: unexpected end of input" where 99 is - the last line of named.conf. - -A: 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. - -Q: I get warning messages like "zone example.com/IN: refresh: failure trying - master 1.2.3.4#53: timed out". - -A: Check that you can make UDP queries from the slave to the master - dig +norec example.com soa @1.2.3.4 +Q: How do I produce a usable core file from a multithreaded named on Linux? - You could be generating queries faster than the slave can cope with. Lower the - serial query rate. +A: If the Linux kernel is 2.4.7 or newer, multithreaded core dumps +are usable (that is, the correct thread is dumped). Otherwise, if using +a 2.2 kernel, apply the kernel patch found in contrib/linux/coredump-patch +and rebuild the kernel. This patch will cause multithreaded programs to dump +the correct thread. - serial-query-rate 5; // default 20 -Q: How do I share a dynamic zone between multiple views? - -A: You choose one view to be master and the second a slave and transfer the zone - between views. - - Master 10.0.1.1: - key "external" { - algorithm hmac-md5; - secret "xxxxxxxx"; - }; - - key "mykey" { - algorithm hmac-md5; - secret "yyyyyyyy"; - }; - - view "internal" { - match-clients { !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; }; - notify-also { 10.0.1.1; }; - }; - }; - - view "external" { - match-clients { 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 { ... }; - }; - }; - -Q: I get a error message like "zone wireless.ietf56.ietf.org/IN: loading master - file primaries/wireless.ietf56.ietf.org: no owner". - -A: This error is produced when a line in the master file contains leading white - space (tab/space) but the 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. - -Q: Why are my logs in GMT (UTC). - -A: You are running chrooted (-t) and have not supplied local timezone information - in the chroot area. - - FreeBSD: /etc/localtime - Solaris: /etc/TIMEZONE and /usr/share/lib/zoneinfo - OSF: /etc/zoneinfo/localtime - - See also tzset(3) and zic(8). - -Q: I get the error message "named: capset failed: Operation not permitted" when - starting named. - -A: The capability module, part of "Linux Security Modules/LSM", has not been - loaded into the kernel. See insmod(8). - -Q: I get "rndc: connect failed: connection refused" when I try to run rndc. - -A: This is usually a configuration error. - - First ensure that named is running and no errors are being reported at startup - (/var/log/messages or equivalent). Running "named -g <usual arguments>" from a - title can help at this point. - - 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. - - 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). - - 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. - -Q: I don't get RRSIG's returned when I use "dig +dnssec". - -A: You need to ensure DNSSEC is enabled (dnssec-enable yes;). - -Q: I get "Error 1067" when starting named under Windows. - -A: This is the service manager saying that named exited. You need to examine the - Application log in the EventViewer to find out why. - - 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. - - options { - Directory "C:\windows\dns\etc"; - }; - -Q: I get "transfer of 'example.net/IN' from 192.168.4.12#53: failed while - receiving responses: permission denied" error messages. - -A: These indicate a filesystem permission error preventing named creating / - renaming the temporary file. These will usually also have other associated - error messages like - - "dumping master file: sl/tmp-XXXX5il3sQ: open: permission denied" - - 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. - - Note file names are relative to the directory specified in options and any - chroot directory ([<chroot dir>/][<options dir>]). - - 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. - - options { - directory "/var/named"; - }; - - zone "example.net" { - type slave; - file "sl/example.net"; - masters { 192.168.4.12; }; - }; - -Q: How do I integrate BIND 9 and Solaris SMF - -A: Sun has a blog entry describing how to do this. - - http://blogs.sun.com/roller/page/anay/Weblog?catname=%2FSolaris - -Q: Can a NS record refer to a CNAME. - -A: No. The rules for glue (copies of the *address* records in the parent zones) - and additional section processing do not allow it to work. - - 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. - -Q: What does "RFC 1918 response from Internet for 0.0.0.10.IN-ADDR.ARPA" mean? +Q: How do I restrict people from looking up the server version? -A: 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 http://as112.net/ for details of the problems you are - causing and the counter measures that have had to be deployed. +A: 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. - 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. - zone "10.IN-ADDR.ARPA" { - type master; - file "empty"; - }; +Q: How do I restrict only remote users from looking up the server +version? - zone "16.172.IN-ADDR.ARPA" { - type master; - file "empty"; - }; +A: 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. - ... + view "chaos" chaos { + match-clients { <those to be refused>; }; + allow-query { none; }; + zone "." { + type hint; + file "/dev/null"; // or any empty file + }; + }; - zone "31.172.IN-ADDR.ARPA" { - type master; - file "empty"; - }; - zone "168.192.IN-ADDR.ARPA" { - type master; - file "empty"; - }; +Q: What do "no source of entropy found" or "could not open entropy source foo" +mean? - empty: - @ 10800 IN SOA <name-of-server>. <contact-email>. ( - 1 3600 1200 604800 10800 ) - @ 10800 IN NS <name-of-server>. +A: 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. - Note - Future versions of named are likely to do this automatically. +Q: I installed BIND 9 and restarted named, but it's still BIND 8. Why? -Q: I'm running BIND on Red Hat Enterprise Linux or Fedora Core - +A: BIND 9 is installed under /usr/local by default. BIND 8 is often +installed under /usr. Check that the correct named is running. - Why can't named update slave zone database files? - Why can't named create DDNS journal files or update the master zones from - journals? +Q: 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? - Why can't named create custom log files? +A: This may be a clock skew problem. Check that the the clocks on +the client and server are properly synchronized (e.g., using ntp). -A: Red Hat Security Enhanced Linux (SELinux) policy security protections : - Red Hat have adopted the National Security Agency's SELinux security policy ( - see http://www.nsa.gov/selinux ) and recommendations for BIND security , which - are more secure than running named in a chroot and make use of the bind-chroot - environment unnecessary . +Q: I'm trying to compile BIND 9, and "make" is failing due to files not +being found. Why? - By default, named is not allowed by the SELinux policy to write, create or - delete any files EXCEPT in these directories: +A: 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. - $ROOTDIR/var/named/slaves - $ROOTDIR/var/named/data - $ROOTDIR/var/tmp +Q: I have a BIND 9 master and a BIND 8.2.3 slave, and the master is +logging error messages like "notify to 10.0.0.1#53 failed: unexpected +end of input". What's wrong? - where $ROOTDIR may be set in /etc/sysconfig/named if bind-chroot is installed. +A: This error message is caused by a known bug in BIND 8.2.3 and is fixed +in BIND 8.2.4. It can be safely ignored - the notify has been acted on by +the slave despite the error message. - The SELinux policy particularly does NOT allow named to modify the $ROOTDIR/var - /named directory, the default location for master zone database files. - 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. +Q: I keep getting log messages like the following. Why? - 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: + 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) - zone "slave.zone." IN { - type slave; - file "slaves/slave.zone.db"; - ... - }; - zone "ddns.zone." IN { - type master; - allow-updates {...}; - file "slaves/ddns.zone.db"; - }; +A: 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. - To allow named to create its cache dump and statistics files, for example, you - could use named.conf options statements such as: +Q: I keep getting log messages like the following. Why? - options { - ... - dump-file "/var/named/data/cache_dump.db"; - statistics-file "/var/named/data/named_stats.txt"; - ... - }; + Jun 21 12:00:00.000 client 10.0.0.1#1234: update denied +A: 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 <http://support.microsoft.com/support/kb/articles/q246/8/04.asp> +for information about how to turn them off. - 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. - You can disable SELinux protection for named entirely by setting the - 'named_disable_trans=1' SELinux tunable boolean parameter. +Q: I see a log message like the following. Why? - The SELinux named policy defines these SELinux contexts for named: + couldn't open pid file '/var/run/named.pid': Permission denied - 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}} +A: 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 named user). - 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 . +Q: When I do a "dig . ns", many of the A records for the root +servers are missing. Why? - To create a custom configuration file location, e.g. '/root/named.conf', to use - with the 'named -c' option, do: +A: 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. - # chcon system_u:object_r:named_conf_t /root/named.conf +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. +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". - To create a custom modifiable named data location, e.g. '/var/log/named' for a - log file, do: - # chcon system_u:object_r:named_cache_t /var/log/named +Q: Zone transfers from my BIND 9 master to my Windows 2000 slave +fail. Why? +A: 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. - To create a custom zone file location, e.g. /root/zones/, do: - # chcon system_u:object_r:named_zone_t /root/zones/{.,*} +Q: Why don't my zones reload when I do an "rndc reload" or SIGHUP? +A: 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. + + +Q: I can query the nameserver from the nameserver but not from other +machines. Why? + +A: This is usually the result of the firewall configuration stopping +the queries and / or the replies. + + +Q: 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. + +A: 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. + + e.g. + 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; + + You put the external address on the alias so that all the other + dns clients on these boxes see the internal view by default. + +A: (BIND 9.3 and later) Use TSIG to select the appropriate view. + + Master 10.0.1.1: + key "external" { + algorithm hmac-md5; + secret "xxxxxxxx"; + }; + view "internal" { + match-clients { !key external; 10.0.1/24; }; + ... + }; + view "external" { + match-clients { key external; any; }; + server 10.0.0.2 { keys external; }; + recursion no; + ... + }; + + Slave 10.0.1.2: + key "external" { + algorithm hmac-md5; + secret "xxxxxxxx"; + }; + view "internal" { + match-clients { !key external; 10.0.1/24; }; + }; + view "external" { + match-clients { key external; any; }; + server 10.0.0.1 { keys external; }; + recursion no; + ... + }; + + +Q: I have Freebsd 4.x and "rndc-confgen -a" just sits there. + +A: /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. + +e.g. + /etc/rc.conf + rand_irqs="3 14 15" + +See also http://people.freebsd.org/~dougb/randomness.html - See these man-pages for more information : selinux(8), named_selinux(8), chcon - (1), setsebool(8) -Q: 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. +Q: Why is named listening on UDP port other than 53? - How do I achieve this ? +A: 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. -A: options { - forward only; - forwarders { <ip.of.primary.nameserver>; }; - }; - zone "sbl-xbl.spamhaus.org" { - type forward; forward only; - forwarders { <ip.of.rbldns.server> port 530; }; - }; +Q: I get error messages like "multiple RRs of singleton type" and +"CNAME and other data" when transferring a zone. What does this mean? - zone "list.dsbl.org" { - type forward; forward only; - forwarders { <ip.of.rbldns.server> port 530; }; - }; +A: 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. + e.g. + dig axfr example.com @master-server > tmp + named-checkzone example.com tmp -Q: Will named be affected by the 2007 changes to daylight savings rules in the US. -A: 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. +Q: I get error messages like "named.conf:99: unexpected end of input" where +99 is the last line of named.conf. - 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. +A: Some text editors (notepad and wordpad) fail to put a line termination +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. - 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. -Q: Why do we get the following warning at run time: +Q: I get warning messages like "zone example.com/IN: refresh: failure trying master +1.2.3.4#53: timed out". - kernel: process `named' is using obsolete setsockopt SO_BSDCOMPAT +A: Check that you can make UDP queries from the slave to the master -A: The early Linux kernels broke sendto() by having it return that a ICMP - unreachable had be received for non connected UDP sockets. This made non - connected UDP sockets work like connected UDP socket which is fine when you are - only talking to one destination. Named however talks to multiple destinations - and it caused problems. + dig +norec example.com soa @1.2.3.4 - Rather than fix sendto() to just have BSD behaviour they added SO_BSDCOMPAT to - turn BSD behaviour on/off on a per socket basis. +A: You could be generating queries faster than the slave can cope with. Lower +the serial query rate. - Later they decided to make BSD behaviour the default and to aggressively track - down applications that used SO_BSDCOMPAT by issuing a warning. This is the sort - of things vendors do in alpha/beta stages of a release so that their code is - clean. They then turn the warning *off* for release code. + serial-query-rate 5; // default 20 - We still have customers that have kernels that require SO_BSDCOMPAT to operate. - We therefore cannot remove the setsockopt(SO_BSDCOMPAT) call. +Q: How do I share a dynamic zone between multiple views? - Now most/all portable applications that use SO_BSDCOMPAT use it conditionally - manner so just removing SO_BSDCOMPAT from the header file would be safe as long - as the binary was not to be moved between systems. BIND's use is conditional. +A: You choose one view to be master and the second a slave and transfer +the zone between views. + + Master 10.0.1.1: + key "external" { + algorithm hmac-md5; + secret "xxxxxxxx"; + }; + + key "mykey" { + algorithm hmac-md5; + secret "yyyyyyyy"; + }; + + view "internal" { + match-clients { !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; }; + notify-also { 10.0.1.1; }; + }; + }; + + view "external" { + match-clients { 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 { ... }; + }; + }; - In short, the Linux developers should either, remove the #define for - SO_BSDCOMPAT, and/or remove the warning. +Q: I get a error message like "zone wireless.ietf56.ietf.org/IN: loading master +file primaries/wireless.ietf56.ietf.org: no owner". -Q: Isn't "make install" supposed to generate a default named.conf? +A: This error is produced when a line in the master file contains leading +white space (tab/space) but the is no current record owner name to inherit +the name from. Usually this is the result of putting white space before +a comment. Forgeting the "@" for the SOA record or indenting the master +file. -A: Short Answer: No. - 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. +Q: Why are my logs in GMT (UTC). - What addresses to listen on? For a laptop on the move a lot you may only want - to listen on the loop back interfaces. +A: You are running chrooted (-t) and have not supplied local timzone +information in the chroot area. - Who do you offer recursive service to? Is there are 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. + FreeBSD: /etc/localtime + Solaris: /etc/TIMEZONE and /usr/share/lib/zoneinfo + OSF: /etc/zoneinfo/localtime + See also tzset(3) and zic(8). |