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- DNS Dynamic Updates (RFC 2136)
- DNS Change Notification (RFC 1996)
- Completely new configuration syntax
- Flexible, categorized logging system
- IP-address-based access control for queries, zone transfers, and updates
that may be specified on a zone-by-zone basis
- More efficient zone transfers
- Improved performance for servers with thousands of zones
- The server no longer forks for outbound zone transfers
- Many bug fixes
BIND 8 is much more configurable than the previous release of BIND. There are
entirely new areas of configuration, such as access control lists and
categorized logging. Many options that previously applied to all zones can now
be used selectively. These features, plus a consideration of future
configuration needs led to the creation of a new configuration file format.
BIND Configuration File Guide — Logging Statement
Syntax
logging {
[ channel channel_name {
( file path_name
[ versions ( number | unlimited ) ]
[ size size_spec ]
| syslog ( kern | user | mail | daemon | auth | syslog | lpr |
news | uucp | cron | authpriv | ftp |
local0 | local1 | local2 | local3 |
local4 | local5 | local6 | local7 )
| null );
[ severity ( critical | error | warning | notice |
info | debug [ level ] | dynamic ); ]
[ print-category yes_or_no; ]
[ print-severity yes_or_no; ]
[ print-time yes_or_no; ]
}; ]
[ category category_name {
channel_name; [ channel_name; ... ]
}; ]
...
};
Definition and Usage
The logging statement configures a wide variety of logging options for the
nameserver. Its channel phrase associates output methods, format options and
severity levels with a name that can then be used with the category phrase to
select how various classes of messages are logged.
Only one logging statement is used to define as many channels and categories
as are wanted. If there are multiple logging statements in a configuration,
the first defined determines the logging, and warnings are issued for the
others. If there is no logging statement, the logging configuration will be:
logging {
category default { default_syslog; default_debug; };
category panic { default_syslog; default_stderr; };
category packet { default_debug; };
category eventlib { default_debug; };
};
The Channel Phrase
All log output goes to one or more "channels"; make as many of them as you
want.
Every channel definition must include a clause that says whether messages
selected for the channel go to a file, to a particular syslog facility, or are
discarded. It can optionally also limit the message severity level that will
be accepted by the channel (default is "info"), and whether to include a
named generated time stamp, the category name and/or severity level
(default is not to include any).
The word null as the destination option for the channel will cause all
messages sent to it to be discarded; other options for the channel are
meaningless.
The file clause can include limitations both on how large the file is allowed
to become, and how many versions of the file will be saved each time the file
is opened.
The size option for files is simply a hard ceiling on log growth. If the file
ever exceeds the size, then named will just not write anything more
to it until the file is reopened; exceeding the size does not automatically
trigger a reopen. The default behavior is to not limit the size of the file.
If you use the version logfile option, then named will retain many
backup versions of the file by renaming them when opening. For example, if you
choose to keep 3 old versions of the file "lamers.log" then just
before it is opened lamers.log.1 is renamed to lames.log.2,
lamers.log.0 is renamed to lamers.log.1, and
lamers.log is renamed to lamers.log.0. No rolled versions
are kept by default. The unlimited keyword is synonymous with 99 in current
BIND releases.
The argument for the syslog clause is a syslog facility described earlier in
this manual. How syslog will handle messages sent to this facility is
described under syslog.conf earlier in this manual. If you have a
system which uses a very old version of syslog and that only uses two
arguments to the openlog() function, then this clause is silently ignored.
The severity clause works like syslog's "priorities", except that they can
also be used if you are writing straight to a file rather than using syslog.
Messages which are not at least of the severity level given will not be
selected for the channel; messages of higher severity levels will be accepted.
If you are using syslog, then the syslog.conf priorities will also
determine what eventually passes through. For example, defining a channel
facility and severity as daemon and debug but only logging
daemon.warning via syslog.conf will cause messages of
severity information and notice to be dropped. If the situation were reversed,
with named writing messages of only warning or higher, then syslog
would print all messages it received from the channel.
The server can supply extensive debugging information when it is in debugging
mode. If the server's global debug level is greater than zero, then debugging
mode will be active. The global debug level is set either by starting the
server with the "-d" flag followed by a positive integer, or by sending the
server the SIGUSR1 signal (for example, by using "ndc trace"). The
global debug level can be set to zero, and debugging mode turned off, by
sending the server the SIGUSR2 signal ("ndc notrace". All debugging
messages in the server have a debug level, and higher debug levels give more
detailed output. Channels that specify a specific debug severity, for example,
channel specific_debug_level {
file "foo";
severity debug 3;
};
will get debugging output of level 3 or less any time the server is in
debugging mode, regardless of the global debugging level. Channels with
dynamic severity use the server's global level to determine what messages to
print.
If print-time has been turned on, then the date and time will be
logged. print-time may be specified for a syslog channel, but is
usually pointless since syslog also prints the date and time. If
print-category is requested, then the category of the message will be
logged as well. Finally, if print-severity is on, then the severity
level of the message will be logged. The print options may be used in any
combination, and will always be printed in the following order: time, category,
and severity. Here is an example where all three print options are on:
28-Apr-1997 15:05:32.863 default: notice: Ready to answer queries.
There are four predefined channels that are used for named's default
logging as follows. How they are used is described in the next section, The
category phrase.
channel default_syslog {
syslog daemon; # send to syslog's daemon facility
severity info; # only send priority info and higher
};
channel default_debug {
file "named.run"; # write to named.run in the working directory
# Note: stderr is used instead of "named.run"
# if the server is started with the "-f" option.
severity dynamic; # log at the server's current debug level };
channel default_stderr { # writes to stderr
file "<stderr>"; # this is illustrative only; there's currently
# no way of specifying an internal file
# descriptor in the configuration language.
severity info; # only send priority info and higher
};
channel null {
null; # toss anything sent to this channel
};
Once a channel is defined, it cannot be redefined. Thus you cannot alter the
built-in channels directly, but you can modify the default logging by pointing
categories at channels you have defined.
The Category Phrase
There are many categories, so you can send the logs you want to see wherever
you want, without seeing logs you don't want. If you don't specify a list of
channels for a category, then log messages in that category will be sent to
the default category instead. If you don't specify a default category, the
following "default" is used:
category default { default_syslog; default_debug; };
As an example, you want to log security events to a file, but you also want
keep the default logging behavior. You'd specify the following:
channel my_security_channel {
file "my_security_file";
severity info
};
category security {
my_security_channel;
default_syslog;
default_debug;
};
To discard all messages in a category, specify the null channel:
category lame-servers { null; };
category cname { null; };
The following categories are available:
- default
- The catch-all. Many things still aren't classified into categories, and
they all end up here. Also, if you don't specify any channels for a
category, the default category is used instead. If you do not define the
default category, the following definition is used:
category default { default_syslog; default_debug; };
- config
- High-level configuration file processing.
- parser
- Low-level configuration file processing.
- queries
- A short log message is generated for every query the server receives.
- lame-servers
- Messages like "Lame server on ..."
- statistics
- Statistics.
- panic
- If the server has to shut itself down due to an internal problem, it
will log the problem in this category as well as in the problem's native
category. If you do not define the panic category, the following
definition is used: category panic { default_syslog; default_stderr;
};
- update
- Dynamic updates.
- ncache
- Negative caching.
- xfer-in
- Zone transfers the server is receiving.
- xfer-out
- Zone transfers the server is sending.
- db
- All database operations.
- eventlib
- Debugging info from the event system. Only one channel may be specified
for this category, and it must be a file channel. If you do not define
the eventlib category, the following definition is used:
category eventlib { default_debug; };
- packet
- Dumps of packets received and sent. Only one channel may be specified
for this category, and it must be a file channel. If you do not define
the packet category, the following definition is used: category
packet { default_debug; };
- notify
- The NOTIFY protocol.
- cname
- Messages like "... points to a CNAME".
- security
- Approved/unapproved requests.
- os
- Operating system problems.
- insist
- Internal consistency check failures.
- maintenance
- Periodic maintenance events.
- load
- Zone loading messages.
- response-checks
- Messages arising from response checking, such as "Malformed response
...", "wrong ans. name ...", "unrelated additional info ...",
"invalid RR type ...", and "bad referral ...".
BIND Configuration File Guide — Zone Statement
Syntax
zone domain_name [ ( in | hs | hesiod | chaos ) ] {
type master;
file path_name;
[ check-names ( warn | fail | ignore ); ]
[ allow-update { address_match_list }; ]
[ allow-query { address_match_list }; ]
[ allow-transfer { address_match_list }; ]
[ notify yes_or_no; ] [ also-notify { ip_addr; [ ip_addr; ... ] };
};
zone domain_name [ ( in | hs | hesiod | chaos ) ]
{ type ( slave | stub );
[ file path_name; ]
masters { ip_addr; [ ip_addr; ... ] };
[ check-names ( warn | fail | ignore ); ]
[ allow-update { address_match_list }; ]
[ allow-query { address_match_list }; ]
[ allow-transfer { address_match_list }; ]
[ max-transfer-time-in number; ]
[ notify yes_or_no; ]
[ also-notify { ip_addr; [ ip_addr; ... ] };
};
zone "." [ ( in | hs | hesiod | chaos ) ] {
type hint;
file path_name;
[ check-names ( warn | fail | ignore ); ]
};
Definition and Usage (Zone Types)
- master
- The master copy of the data in a zone.
- slave
- A slave zone is a replica of a master zone. The masters list specifies
one or more IP addresses that the slave contacts to update its copy of
the zone. If file is specified, then the replica will be written to the
file. Use of file is recommended, since it often speeds server startup
and eliminates a needless waste of bandwidth.
- stub
- A stub zone is like a slave zone, except that it replicates only the NS
records of a master zone instead of the entire zone.
- hint
- The initial set of root nameservers is specified using a hint zone. When
the server starts up, it uses the root hints to find a root nameserver
and get the most recent list of root nameservers.
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NOTE: Previous releases of BIND used the term primary for a master
zone, secondary for a slave zone, and cache for a hint zone.
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Class
The zone's name may optionally be followed by a class. If a class is not
specified, class in is used.
Options
- check-names
- See Name Checking.
- allow-query
- See the description of allow-query in the Access Control section.
- allow-update
- Specifies which hosts are allowed to submit Dynamic DNS updates to the
server. The default is to deny updates from all hosts.
- allow- transfer
- See the description of allow-transfer in the Access Control section.
- max-transfer-time-in
- See the description of max-transfer-time-in in the Zone
Transfers section.
- notify
- See the description of notify in the Boolean Options section.
- also-notify
- also-notify is only meaningful if notify is active for this
zone.
The set of machines that will receive a DNS NOTIFY message for this zone
is made up of all the listed nameservers for the zone (other than the
primary master) plus any IP addresses specified with
also-notify.
also-notify is not meaningful for stub
zones. The default is the empty list.
BIND Configuration File Guide — Options Statement
Syntax
options {
[ directory path_name; ]
[ named-xfer path_name; ]
[ dump-file path_name; ]
[ memstatistics-file path_name; ]
[ pid-file path_name; ]
[ statistics-file path_name; ]
[ auth-nxdomain yes_or_no; ]
[ deallocate-on-exit yes_or_no; ]
[ fake-iquery yes_or_no; ]
[ fetch-glue yes_or_no; ]
[ host-statistics yes_or_no; ]
[ multiple-cnames yes_or_no; ]
[ notify yes_or_no; ]
[ recursion yes_or_no; ]
[ forward ( only | first ); ]
[ forwarders { [ in_addr ; [ in_addr ; ... ] ] }; ]
[ check-names ( master | slave | response ) ( warn | fail | ignore); ]
[ allow-query { address_match_list }; ]
[ allow-transfer { address_match_list }; ]
[ listen-on [ port ip_port ] { address_match_list }; ]
[ query-source [ address ( ip_addr | * ) ]
[ port ( ip_port | * ) ] ; ]
[ max-transfer-time-in number; ]
[ transfer-format ( one-answer | many-answers ); ]
[ transfers-in number; ]
[ transfers-out number; ]
[ transfers-per-ns number; ]
[ coresize size_spec ; ]
[ datasize size_spec ; ]
[ files size_spec ; ]
[ stacksize size_spec ; ]
[ cleaning-interval number; ]
[ interface-interval number; ]
[ statistics-interval number; ]
[ topology { address_match_list }; ]
};
Definition and Use
The options statement sets up global options to be used by BIND. This
statement may appear at only once in a configuration file; if more than one
occurrence is found, the first occurrence determines the actual options used,
and a warning will be generated. If there is no options statement, an options
block with each option set to its default will be used.
Pathnames
- directory
- The working directory of the server. Any non-absolute pathnames in the
configuration file will be taken as relative to this directory. The
default location for most server output files, for example,
"named.run" is this directory. If a directory is not specified,
the working directory defaults to ".", the directory from which the
server was started. The directory specified should be an absolute
path.
- named-xfer
- The pathname to the named-xfer program that the server uses for
inbound zone transfers. If not specified, the default is system
dependent for example, "/usr/sbin/named-xfer".
- dump-file
- The pathname of the file the server dumps the database to when it
receives SIGINT signal (ndc dumpdb). If not specified, the
default is "named_dump.db".
- memstatistics- file
- The pathname of the file the server writes memory usage statistics to on
exit, if deallocate-on-exit is yes. If not specified, the
default is "named.memstats".
- pid-file
- The pathname of the file the server writes its process ID in. If not
specified, the default is operating system dependent, but is usually
"/var/run/named.pid" or "/etc/named.pid". The pid-file
is used by programs like "ndc" that want to send signals to the running
nameserver.
- statistics- file
- The pathname of the file the server appends statistics to when it
receives SIGILL signal (ndc stats). If not specified, the
default is "named.stats".
Boolean Options
- auth-nxdomain
- If yes, then the AA bit is always set on NXDOMAIN
responses, even if the server is not actually authoritative. The default
is yes. Do not turn off auth-nxdomain unless you are sure you
know what you are doing, as some older software won't like it.
- deallocate-on- exit
- If yes, then when the server exits it will painstakingly deallocate
every object it allocated, and then write a memory usage report to the
memstatistics-file. The default is no, because it is faster to
let the operating system clean up. deallocate-on-exit is handy
for detecting memory leaks.
- fake-iquery
- If yes, the server will simulate the obsolete DNS query type
IQUERY. The default is no.
- fetch-glue
- If yes (the default), the server will fetch "glue" resource records it
doesn't have when constructing the additional data section of a response.
fetch-glue no can be used in conjunction with
recursion no to prevent the server's cache from growing or
becoming corrupted (at the cost of requiring more work from the
client).
- host- statistics
- If yes, then statistics are kept for every host that the nameserver
interacts with. The default is no.
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NOTE: Turning on host-statistics can consume huge amounts of memory.
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- multiple- cnames
- If yes, then multiple CNAME resource records will be allowed
for a domain name. The default is no. Allowing multiple CNAME
records is against standards and is not recommended. Multiple
CNAME support is available because previous versions of BIND
allowed multiple CNAME records, and these records have been
used for load balancing by a number of sites.
- notify
- If yes (the default), DNS NOTIFY messages are sent when a zone
the server is authoritative for changes. The use of NOTIFY
speeds convergence between the master and its slaves. Slave servers that
receive a NOTIFY message and understand it, will contact the
master server for the zone and see if they need to do a zone transfer,
and if they do, they will initiate it immediately. The notify option may
also be specified in the zone statement, in which case it overrides the
options notify statement.
- recursion
- If yes, and a DNS query requests recursion, then the server will attempt
to do all the work required to answer the query. If recursion is not on,
the server will return a referral to the client if it doesn't know the
answer. The default is yes. See also fetch-glue.
Forwarding
The forwarding facility can be used to create a large sitewide cache on a few
servers, reducing traffic over links to external nameservers. It can also be
used to allow queries by servers that do not have direct access to the
Internet, but wish to look up exterior names anyway. Forwarding occurs only on
those queries for which the server is not authoritative and does not have the
answer in its cache.
- forward
- This option is only meaningful if the forwarders list is not empty. A
value of first, the default, causes the server to query the forwarders
first, and if that doesn't answer the question the server will then look
for the answer itself. If only is specified, the server will only query
the forwarders.
- forwarders
- Specifies the IP addresses to be used for forwarding. The default is the
empty list (no forwarding).
Future versions of BIND 8 will provide a more powerful forwarding system. The
syntax described above will continue to be supported.
Name Checking
The server can check domain names based upon their expected client contexts.
For example, a domain name used as a hostname can be checked for compliance
with the RFCs defining valid hostnames.
Three checking methods are available:
- ignore
- No checking is done.
- warn
- Names are checked against their expected client contexts. Invalid names
are logged, but processing continues normally.
- fail
- Names are checked against their expected client contexts. Invalid names
are logged, and the offending data is rejected.
The server can check names in three areas; master zone files, slave zone files,
and in responses to queries the server has initiated. If check-names
response fail has been specified, and answering the client's question
would require sending an invalid name to the client, the server will send a
REFUSED response code to the client.
The defaults are:
check-names master fail;
check-names slave warn;
check-names response ignore;
check-names may also be specified in the zone statement, in which
case it overrides the options check-names statement. When used in a
zone statement, the area is not specified (because it can be deduced from the
zone type).
Access Control
Access to the server can be restricted based on the IP address of the
requesting system. See address_match_list for details on how to
specify IP address lists.
- allow-query
- Specifies which hosts are allowed to ask ordinary questions.
allow-query may also be specified in the zone statement, in
which case it overrides the options allow-query statement. If
not specified, the default is to allow queries from all hosts.
- allow-transfer
- Specifies which hosts are allowed to receive zone transfers from the
server. allow-transfer may also be specified in the zone
statement, in which case it overrides the options
allow-transfer statement. If not specified, the default is to
allow transfers from all hosts.
Interfaces
The interfaces and ports that the server will answer queries from may be
specified using the listen-on option. listen-on takes an
optional port, and an address_match_list. The server will listen on
all interfaces allowed by the address match list. If a port is not specified,
port 53 will be used.
Multiple listen-on statements are allowed. For example:
listen-on { 5.6.7.8; };
listen-on port 1234 { !1.2.3.4; 1.2/16; };
If no listen-on is specified, the server will listen on port 53 on
all interfaces.
Query Address
If the server doesn't know the answer to a question, it will query other
nameservers. query-source specifies the address and port used for
such queries. If address is * or is omitted, a wildcard IP address
(INADDR_ANY) will be used. If port is * or is omitted, a random
unprivileged port will be used. The default is
query-source address * port *;
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NOTE: Query-source currently applies only to UDP queries; TCP queries
always use a wildcard IP address and a random unprivileged port.
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Zone Transfers
- max-transfer- time-in
- Inbound zone transfers (named-xfer processes) running longer
than this many minutes will be terminated. The default is 120 minutes
(2 hours).
- transfer- format
- The server supports two zone transfer methods. one-answer uses
one DNS message per resource record transferred. many-answers
packs as many resource records as possible into a message.
many-answers is more efficient, but is only known to be
understood by BIND 8.1 and patched versions of BIND 4.9.5. The default
is one-answer. transfer-format may be overridden on a
per-server basis by using the server statement.
- transfers-in
- The maximum number of inbound zone transfers that can be running
concurrently. The default value is 10. Increasing transfers-in
may speed up the convergence of slave zones, but it also may increase
the load on the local system.
- transfers-out
- This option will be used in the future to limit the number of concurrent
outbound zone transfers. It is checked for syntax, but is otherwise
ignored.
- transfers-per-ns
- The maximum number of inbound zone transfers (named-xfer
processes) that can be concurrently transferring from a given remote
nameserver. The default value is 2. Increasing transfers-per-ns
may speed up the convergence of slave zones, but it also may increase
the load on the remote nameserver. transfers-per-ns may be
overridden on a per-server basis by using the transfers phrase
of the server statement.
Resource Limits
The server's usage of many system resources can be limited. Some operating
systems don't support some of the limits. On such systems, a warning will be
issued if the unsupported limit is used. Some operating systems don't support
limiting resources, and on these systems a cannot set resource limits on this
system message will be logged.
Scaled values are allowed when specifying resource limits. For example,
1G can be used instead of 1073741824 to specify a limit of
one gigabyte. unlimited requests unlimited use, or the maximum available
amount. default uses the limit that was in force when the server was started.
See size_spec for more details.
- coresize
- The maximum size of a core dump. The default is default.
- datasize
- The maximum amount of data memory the server may use. The default is
default.
- files
- The maximum number of files the server may have open concurrently. The
default is unlimited.
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NOTE: On some operating systems the server cannot set an unlimited
value and cannot determine the maximum number of open files the kernel can
support. On such systems, choosing unlimited will cause the server to use
the larger of the rlim_max for RLIMIT_NOFILE and the value returned by
sysconf (_SC_OPEN_MAX). If the actual kernel limit is larger than this
value, use limit files to specify the limit explicitly.
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- stacksize
- The maximum amount of stack memory the server may use. The default is
default.
Periodic Task Intervals
- cleaning- interval
- The server will remove expired resource records from the cache every
cleaning-interval minutes. The default is 60 minutes. If set to
0, no periodic cleaning will occur.
- interface- interval
- The server will scan the network interface list every
interface-interval minutes. The default is 60 minutes. If set
to 0, interface scanning will only occur when the configuration file is
loaded. After the scan, listeners will be started on any new interfaces
(provided they are allowed by the listen-on configuration).
Listeners on interfaces that have gone away will be cleaned up.
- statistics- interval
- Nameserver statistics will be logged every statistics-interval
minutes. The default is 60. If set to 0, no statistics will be
logged.
Topology
All other things being equal, when the server chooses a nameserver to query
from a list of nameservers, it prefers the one that is topologically closest
to itself. The topology statement takes an address_match_list and
interprets it in a special way. Each top-level list element is assigned a
distance. Non-negated elements get a distance based on their position in the
list, where the closer the match is to the start of the list, the shorter the
distance is between it and the server. A negated match will be assigned the
maximum distance from the server. If there is no match, the address will get a
distance which is further than any non-negated list element, and closer than
any negated element. For example,
topology {
10/8;
!1.2.3/24;
{ 1.2/16; 3/8; };
};
will prefer servers on network 10 the most, followed by hosts on network
1.2.0.0 (netmask 255.255.0.0) and network 3, with
the exception of hosts on network 1.2.3 (netmask 255.255.255.0),
which is preferred least of all.
The default topology is
topology { localhost; localnets; };
Converting From BIND 4.9.x
BIND 4.9.x configuration files can be converted to the new format by using
src/bin/named/named-bootconf.pl, a perl script that is part of the
BIND 8.1 source kit.
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