diff --git a/FAQ.xml b/FAQ.xml new file mode 100644 index 0000000000..5b6de5870c --- /dev/null +++ b/FAQ.xml @@ -0,0 +1,917 @@ + +
+ Frequently Asked Questions about BIND 9 + + + + + Why doesn't -u work on Linux 2.2.x when I build with + --enable-threads? + + + + + 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. + + + 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. + + + If Linux threads ever work correctly, this restriction will + go away. + + + Configuring BIND9 with the --disable-threads option (the + default) causes a non-threaded version to be built, which + will allow -u to be used. + + + + + + + + Why does named log the warning message no TTL specified - + using SOA MINTTL instead? + + + + + 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: + + + +example.com. 86400 IN SOA ns hostmaster ( 1 3600 1800 1814400 3600 ) + + + + + + + + Why do I see 5 (or more) copies of named on Linux? + + + + + 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. + + + + + + + + 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? + + + + + 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. + + + + + + + + Why do I get errors like dns_zone_load: zone foo/IN: loading + master file bar: ran out of space? + + + + + 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. + + + + + + + + How do I produce a usable core file from a multithreaded + named on Linux? + + + + + 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. + + + + + + + + How do I restrict people from looking up the server version? + + + + + 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. + + + + + + + + How do I restrict only remote users from looking up the + server version? + + + + + 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 + }; +}; + + + + + + + + What do no source of entropy found or could not + open entropy source foo mean? + + + + + 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. + + + + + + + + I installed BIND 9 and restarted named, but it's still BIND 8. Why? + + + + + BIND 9 is installed under /usr/local by default. BIND 8 + is often installed under /usr. Check that the correct named + is running. + + + + + + + + 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? + + + + + This may be a clock skew problem. Check that the the clocks + on the client and server are properly synchronised (e.g., + using ntp). + + + + + + + + I'm trying to compile BIND 9, and "make" is failing due to + files not being found. Why? + + + + + 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. + + + + + + + + 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? + + + + + 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. + + + + + + + + I keep getting log messages like the following. Why? + + + 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) + + + + + 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. + + + + + + + + I keep getting log messages like the following. Why? + + + Jun 21 12:00:00.000 client 10.0.0.1#1234: update denied + + + + + 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. + + + + + + + + I see a log message like the following. Why? + + + couldn't open pid file '/var/run/named.pid': Permission denied + + + + + 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). + + + + + + + + When I do a "dig . ns", many of the A records for the root + servers are missing. Why? + + + + + 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". + + + + + + + + Zone transfers from my BIND 9 master to my Windows 2000 + slave fail. Why? + + + + + 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. + + + + + + + + Why don't my zones reload when I do an "rndc reload" or SIGHUP? + + + + + 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. + + + + + + + + I can query the nameserver from the nameserver but not from other + machines. Why? + + + + + This is usually the result of the firewall configuration stopping + the queries and / or the replies. + + + + + + + + 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. + + + + + 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. + + + + + 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; + ... + }; + + + + + + + + I have FreeBSD 4.x and "rndc-confgen -a" just sits there. + + + + + /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 + + + + + + + + + Why is named listening on UDP port other than 53? + + + + + 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. + + + + + + + + I get error messages like multiple RRs of singleton type + and CNAME and other data when transferring a zone. What + does this mean? + + + + + 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 + + + + + + + + I get error messages like named.conf:99: unexpected end + of input where 99 is the last line of named.conf. + + + + + 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. + + + + + + + + I get warning messages like zone example.com/IN: refresh: + failure trying master 1.2.3.4#53: timed out. + + + + + Check that you can make UDP queries from the slave to the master + + + +dig +norec example.com soa @1.2.3.4 + + + You could be generating queries faster than the slave can + cope with. Lower the serial query rate. + + + +serial-query-rate 5; // default 20 + + + + + + + + How do I share a dynamic zone between multiple views? + + + + + 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 { ... }; + }; + }; + + + + + + + + I get a error message like zone wireless.ietf56.ietf.org/IN: + loading master file primaries/wireless.ietf56.ietf.org: no + owner. + + + + + 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. + + + + + + + + Why are my logs in GMT (UTC). + + + + + You are running chrooted (-t) and have not supplied local timzone + 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). + + + + + + + + I get the error message named: capset failed: Operation + not permitted when starting named. + + + + + The capset module has not been loaded into the kernel. See + insmod(8). + + + + + + + + I get rndc: connect failed: connection refused when + I try to run rndc. + + + + + 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. + + + + + + + + I don't get RRSIG's returned when I use "dig +dnssec". + + + + + You need to ensure DNSSEC is enabled (dnssec-enable yes;). + + + + + + + + I get Error 1067 when starting named under Windows. + + + + + 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"; +}; + + + + + + + + I get transfer of 'example.net/IN' from 192.168.4.12#53: + failed while receiving responses: permission denied error + messages. + + + + + 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; }; +} + + + + + + + + How do I intergrate BIND 9 and Solaris SMF + + + + + Sun has a blog entry describing how to do this. + + + + http://blogs.sun.com/roller/page/anay/Weblog?catname=%2FSolaris + + + + + + + + + Can a NS record refer to a CNAME. + + + + + 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 namesever implementation supports either of + these requirements. + + + + + +