diff options
Diffstat (limited to 'contrib/bind9/FAQ')
| -rw-r--r-- | contrib/bind9/FAQ | 395 |
1 files changed, 251 insertions, 144 deletions
diff --git a/contrib/bind9/FAQ b/contrib/bind9/FAQ index 9b806cb..5c6a2a7 100644 --- a/contrib/bind9/FAQ +++ b/contrib/bind9/FAQ @@ -4,26 +4,36 @@ Frequently Asked Questions about BIND 9 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. +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. 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. + 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. + 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. +Q: Why do I get the following errors: + + 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 + +A: This is the result of a Linux kernel bug. + + 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"? @@ -40,23 +50,26 @@ A: Your zone file is illegal according to RFC1035. It must either have a line 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. + 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. +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"? +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. +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 multithreaded named on Linux? @@ -68,16 +81,16 @@ A: If the Linux kernel is 2.4.7 or newer, multithreaded core dumps are usable 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. +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. +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>; }; @@ -91,48 +104,45 @@ A: The following view statement will intercept lookups as the internal view 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. +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? +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: This may be a clock skew problem. Check that the the clocks on the client - and server are properly synchronised (e.g., using ntp). +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? 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. + doesn't work. If you are using one of these, use normal make or gmake instead. -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? +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. +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: 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) + 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/ +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? @@ -140,11 +150,11 @@ 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. + 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? @@ -152,59 +162,59 @@ Q: I see a log message like the following. Why? 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. + 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". + 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. +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. +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. +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. + 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. +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: @@ -232,8 +242,8 @@ A: You will need to give the master and slave multiple IP addresses and use 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. + 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. @@ -248,7 +258,7 @@ A: BIND 9.3 and later: Use TSIG to select the appropriate view. }; view "external" { match-clients { key external; any; }; - server 10.0.0.2 { keys external; }; + server 10.0.1.2 { keys external; }; recursion no; ... }; @@ -264,7 +274,7 @@ A: BIND 9.3 and later: Use TSIG to select the appropriate view. }; view "external" { match-clients { key external; any; }; - server 10.0.0.1 { keys external; }; + server 10.0.1.1 { keys external; }; recursion no; ... }; @@ -272,8 +282,8 @@ A: BIND 9.3 and later: Use TSIG to select the appropriate view. 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. + 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" @@ -283,34 +293,33 @@ A: /dev/random is not configured. Use rndcontrol(8) to tell the kernel to use 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. + 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? +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. + 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 existance (NSEC). + A CNAME record cannot exist with the same name as another record except for the + DNSSEC records which prove its existance (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." + 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. +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. + (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". @@ -319,15 +328,15 @@ A: 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. + You could be generating queries faster than the slave can cope with. Lower the + serial query rate. 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. +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" { @@ -370,14 +379,14 @@ 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. Forgeting the "@" for the SOA record or indenting the master file. + 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. Q: Why are my logs in GMT (UTC). -A: You are running chrooted (-t) and have not supplied local timzone - information in the chroot area. +A: 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 @@ -395,23 +404,23 @@ 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. + 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. + -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. + 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". @@ -419,12 +428,11 @@ 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. +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. + 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"; @@ -439,11 +447,11 @@ A: These indicate a filesystem permission error preventing named creating / "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. + 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>]). @@ -489,8 +497,8 @@ A: If the IN-ADDR.ARPA name covered refers to a internal address space you are 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. + 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; @@ -523,3 +531,102 @@ A: If the IN-ADDR.ARPA name covered refers to a internal address space you are Future versions of named are likely to do this automatically. +Q: I'm running BIND on Red Hat Enterprise Linux or Fedora Core - + + Why can't named update slave zone database files? + + Why can't named create DDNS journal files or update the master zones from + journals? + + Why can't named create custom log files? + +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 unecessary . + + By default, named is not allowed by the SELinux policy to write, create or + delete any files EXCEPT in these directories: + + $ROOTDIR/var/named/slaves + $ROOTDIR/var/named/data + $ROOTDIR/var/tmp + + + where $ROOTDIR may be set in /etc/sysconfig/named if bind-chroot is installed. + + 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. + + 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: + + zone "slave.zone." IN { + type slave; + file "slaves/slave.zone.db"; + ... + }; + zone "ddns.zone." IN { + type master; + allow-updates {...}; + file "slaves/ddns.zone.db"; + }; + + + To allow named to create its cache dump and statistics files, for example, you + could use named.conf options statements such as: + + options { + ... + dump-file "/var/named/data/cache_dump.db"; + statistics-file "/var/named/data/named_stats.txt"; + ... + }; + + + 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. + + The SELinux named policy defines these SELinux contexts for named: + + 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}} + + + 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 . + + To create a custom configuration file location, eg. '/root/named.conf', to use + with the 'named -c' option, do: + + # chcon system_u:object_r:named_conf_t /root/named.conf + + + To create a custom modifiable named data location, eg. '/var/log/named' for a + log file, do: + + # chcon system_u:object_r:named_cache_t /var/log/named + + + To create a custom zone file location, eg. /root/zones/, do: + + # chcon system_u:object_r:named_zone_t /root/zones/{.,*} + + + See these man-pages for more information : selinux(8), named_selinux(8), chcon + (1), setsebool(8) + |
