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Mark Andrews
2005-11-30 03:20:40 +00:00
parent 7105163938
commit 91be6c5ba2
2 changed files with 162 additions and 124 deletions
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263
FAQ
View File

@@ -1,56 +1,67 @@
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 does named log the warning message "no TTL specified - using SOA MINTTL
instead"?
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"?
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.
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.
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.
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"?
@@ -62,22 +73,23 @@ Q: How do I produce a usable core file from a multithreaded named on Linux?
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.
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.
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.
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.
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>; };
@@ -88,8 +100,8 @@ 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?
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
@@ -112,13 +124,13 @@ A: This may be a clock skew problem. Check that the the clocks on the client
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
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.
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?
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
@@ -126,14 +138,14 @@ A: This error message is caused by a known bug in BIND 8.2.3 and is fixed in
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
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.
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?
@@ -150,12 +162,12 @@ 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).
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?
@@ -165,43 +177,46 @@ A: This is normal and harmless. It is a somewhat confusing side effect of the
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.
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".
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.
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?
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.
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.
@@ -232,8 +247,8 @@ 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.
@@ -272,8 +287,8 @@ 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"
@@ -282,35 +297,37 @@ 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.
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.
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."
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.
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.
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".
@@ -366,13 +383,14 @@ A: You choose one view to be master and the second a slave and transfer the
};
};
Q: I get a error message like "zone wireless.ietf56.ietf.org/IN: loading master
file primaries/wireless.ietf56.ietf.org: no owner".
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.
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.
Q: Why are my logs in GMT (UTC).
@@ -385,8 +403,8 @@ A: You are running chrooted (-t) and have not supplied local timzone
See also tzset(3) and zic(8).
Q: I get the error message "named: capset failed: Operation not permitted" when
starting named.
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).
@@ -399,19 +417,19 @@ A: This is usually a configuration error.
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.
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).
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".
@@ -448,9 +466,9 @@ A: These indicate a filesystem permission error preventing named creating /
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.
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";
@@ -470,22 +488,23 @@ A: Sun has a blog entry describing how to do this.
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.
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 namesever implementation supports either of
these requirements.
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.
Q: What does "RFC 1918 response from Internet for 0.0.0.10.IN-ADDR.ARPA" mean?
Q: What does "RFC 1918 response from Internet for 0.0.0.10.IN-ADDR.ARPA"
mean?
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 quering 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: 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 quering 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.
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

23
FAQ.xml
View File

@@ -17,7 +17,7 @@
- PERFORMANCE OF THIS SOFTWARE.
-->
<!-- $Id: FAQ.xml,v 1.7 2005/11/02 23:32:40 marka Exp $ -->
<!-- $Id: FAQ.xml,v 1.8 2005/11/30 03:20:40 marka Exp $ -->
<article class="faq">
<title>Frequently Asked Questions about BIND 9</title>
@@ -64,6 +64,26 @@
</answer>
</qandaentry>
<qandaentry>
<question>
<para>
Why do I get the following errors:
<programlisting>general: errno2result.c:109: unexpected error:
general: unable to convert errno to isc_result: 14: Bad address
client: UDP client handler shutting down due to fatal receive error: unexpected error</programlisting>
</para>
</question>
<answer>
<para>
This is the result of a Linux kernel bug.
</para>
<para>
See:
<ulink url="http://marc.theaimsgroup.com/?l=linux-netdev&amp;m=113081708031466&amp;w=2">http://marc.theaimsgroup.com/?l=linux-netdev&amp;m=113081708031466&amp;w=2</ulink>
</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>
@@ -1002,6 +1022,5 @@ empty:
</note>
</answer>
</qandaentry>
</qandaset>
</article>