Table of Contents
BIND 9 configuration is broadly similar to BIND 8; however, there are a few new areas of configuration, such as views. BIND 8 configuration files should work with few alterations in BIND 9, although more complex configurations should be reviewed to check if they can be more efficiently implemented using the new features found in BIND 9.
BIND 4 configuration files can be converted to the new format
using the shell script
contrib/named-bootconf/named-bootconf.sh.
Following is a list of elements used throughout the BIND configuration file documentation:
|
The name of an |
|
A list of one or more |
|
A quoted string which will be used as
a DNS name, for example " |
|
One to four integers valued 0 through 255 separated by dots (`.'), such as 123, 45.67 or 89.123.45.67. |
|
An IPv4 address with exactly four elements
in |
|
An IPv6 address, such as 2001:db8::1234. IPv6 scoped addresses that have ambiguity on their scope zones must be disambiguated by an appropriate zone ID with the percent character (`%') as delimiter. It is strongly recommended to use string zone names rather than numeric identifiers, in order to be robust against system configuration changes. However, since there is no standard mapping for such names and identifier values, currently only interface names as link identifiers are supported, assuming one-to-one mapping between interfaces and links. For example, a link-local address fe80::1 on the link attached to the interface ne0 can be specified as fe80::1%ne0. Note that on most systems link-local addresses always have the ambiguity, and need to be disambiguated. |
|
An |
|
An IP port |
|
An IP network specified as an |
|
A |
|
A list of one or more |
|
A non-negative 32 bit integer (i.e., a number between 0 and 4294967295, inclusive). Its acceptable value might further be limited by the context in which it is used. |
|
A quoted string which will be used as
a pathname, such as |
|
A number, the word
An A The value must be representable as a 64-bit unsigned integer
(0 to 18446744073709551615, inclusive).
Using |
|
Either |
|
One of |
address_match_list= address_match_list_element ; [ address_match_list_element; ... ]address_match_list_element= [ ! ] (ip_address [/length] | key key_id | acl_name | { address_match_list } )
Address match lists are primarily used to determine access control for various server operations. They are also used in the listen-on and sortlist statements. The elements which constitute an address match list can be any of the following:
Elements can be negated with a leading exclamation mark (`!'), and the match list names "any", "none", "localhost", and "localnets" are predefined. More information on those names can be found in the description of the acl statement.
The addition of the key clause made the name of this syntactic element something of a misnomer, since security keys can be used to validate access without regard to a host or network address. Nonetheless, the term "address match list" is still used throughout the documentation.
When a given IP address or prefix is compared to an address match list, the list is traversed in order until an element matches. The interpretation of a match depends on whether the list is being used for access control, defining listen-on ports, or in a sortlist, and whether the element was negated.
When used as an access control list, a non-negated match allows access and a negated match denies access. If there is no match, access is denied. The clauses allow-notify, allow-query, allow-transfer, allow-update, allow-update-forwarding, and blackhole all use address match lists this. Similarly, the listen-on option will cause the server to not accept queries on any of the machine's addresses which do not match the list.
Because of the first-match aspect of the algorithm, an element that defines a subset of another element in the list should come before the broader element, regardless of whether either is negated. For example, in 1.2.3/24; ! 1.2.3.13; the 1.2.3.13 element is completely useless because the algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24 element. Using ! 1.2.3.13; 1.2.3/24 fixes that problem by having 1.2.3.13 blocked by the negation but all other 1.2.3.* hosts fall through.
The BIND 9 comment syntax allows for comments to appear anywhere that white space may appear in a BIND configuration file. To appeal to programmers of all kinds, they can be written in the C, C++, or shell/perl style.
/* This is a BIND comment as in C */
// This is a BIND comment as in C++
# This is a BIND comment as in common UNIX shells and perl
Comments may appear anywhere that whitespace may appear in a BIND configuration file.
C-style comments start with the two characters /* (slash, star) and end with */ (star, slash). Because they are completely delimited with these characters, they can be used to comment only a portion of a line or to span multiple lines.
C-style comments cannot be nested. For example, the following is not valid because the entire comment ends with the first */:
/* This is the start of a comment. This is still part of the comment. /* This is an incorrect attempt at nesting a comment. */ This is no longer in any comment. */
C++-style comments start with the two characters // (slash, slash) and continue to the end of the physical line. They cannot be continued across multiple physical lines; to have one logical comment span multiple lines, each line must use the // pair.
For example:
// This is the start of a comment. The next line // is a new comment, even though it is logically // part of the previous comment.
Shell-style (or perl-style, if you prefer) comments start
with the character # (number sign) and continue to the end of the
physical line, as in C++ comments.
For example:
# This is the start of a comment. The next line # is a new comment, even though it is logically # part of the previous comment.
You cannot use the semicolon (`;') character to start a comment such as you would in a zone file. The semicolon indicates the end of a configuration statement.
A BIND 9 configuration consists of statements and comments. Statements end with a semicolon. Statements and comments are the only elements that can appear without enclosing braces. Many statements contain a block of sub-statements, which are also terminated with a semicolon.
The following statements are supported:
acl |
defines a named IP address matching list, for access control and other uses. |
controls |
declares control channels to be used by the rndc utility. |
include |
includes a file. |
key |
specifies key information for use in authentication and authorization using TSIG. |
logging |
specifies what the server logs, and where the log messages are sent. |
lwres |
configures named to also act as a light weight resolver daemon (lwresd). |
masters |
defines a named masters list for inclusion in stub and slave zone masters clauses. |
options |
controls global server configuration options and sets defaults for other statements. |
server |
sets certain configuration options on a per-server basis. |
trusted-keys |
defines trusted DNSSEC keys. |
view |
defines a view. |
zone |
defines a zone. |
The logging and options statements may only occur once per configuration.
The acl statement assigns a symbolic name to an address match list. It gets its name from a primary use of address match lists: Access Control Lists (ACLs).
Note that an address match list's name must be defined with acl before it can be used elsewhere; no forward references are allowed.
The following ACLs are built-in:
any |
Matches all hosts. |
none |
Matches no hosts. |
localhost |
Matches the IPv4 and IPv6 addresses of all network interfaces on the system. |
localnets |
Matches any host on an IPv4 or IPv6 network for which the system has an interface. Some systems do not provide a way to determine the prefix lengths of local IPv6 addresses. In such a case, localnets only matches the local IPv6 addresses, just like localhost. |
controls { inet ( ip_addr | * ) [ port ip_port ] allow {address_match_list} keys {key_list}; [ inet ...; ] };
The controls statement declares control channels to be used by system administrators to control the operation of the name server. These control channels are used by the rndc utility to send commands to and retrieve non-DNS results from a name server.
An inet control channel is a TCP
socket listening at the specified
ip_port on the specified
ip_addr, which can be an IPv4 or IPv6
address. An ip_addr
of * is interpreted as the IPv4 wildcard
address; connections will be accepted on any of the system's
IPv4 addresses. To listen on the IPv6 wildcard address,
use an ip_addr of ::.
If you will only use rndc on the local host,
using the loopback address (127.0.0.1
or ::1) is recommended for maximum
security.
If no port is specified, port 953
is used. "*" cannot be used for
ip_port.
The ability to issue commands over the control channel is restricted by the allow and keys clauses. Connections to the control channel are permitted based on the address_match_list. This is for simple IP address based filtering only; any key_id elements of the address_match_list are ignored.
The primary authorization mechanism of the command channel is the key_list, which contains a list of key_ids. Each key_id in the key_list is authorized to execute commands over the control channel. See Remote Name Daemon Control application in the section called “Administrative Tools”) for information about configuring keys in rndc.
If no controls statement is present,
named will set up a default
control channel listening on the loopback address 127.0.0.1
and its IPv6 counterpart ::1.
In this case, and also when the controls statement
is present but does not have a keys clause,
named will attempt to load the command channel key
from the file rndc.key in
/etc (or whatever sysconfdir
was specified as when BIND was built).
To create a rndc.key file, run
rndc-confgen -a.
The rndc.key feature was created to
ease the transition of systems from BIND 8,
which did not have digital signatures on its command channel messages
and thus did not have a keys clause.
It makes it possible to use an existing BIND 8
configuration file in BIND 9 unchanged,
and still have rndc work the same way
ndc worked in BIND 8, simply by executing the
command rndc-confgen -a after BIND 9 is
installed.
Since the rndc.key feature
is only intended to allow the backward-compatible usage of
BIND 8 configuration files, this feature does not
have a high degree of configurability. You cannot easily change
the key name or the size of the secret, so you should make a
rndc.conf with your own key if you wish to change
those things. The rndc.key file also has its
permissions set such that only the owner of the file (the user that
named is running as) can access it. If you
desire greater flexibility in allowing other users to access
rndc commands then you need to create an
rndc.conf and make it group readable by a group
that contains the users who should have access.
The UNIX control channel type of BIND 8 is not supported in BIND 9, and is not expected to be added in future releases. If it is present in the controls statement from a BIND 8 configuration file, it is ignored and a warning is logged.
To disable the command channel, use an empty controls statement: controls { };.
The include statement inserts the specified file at the point where the include statement is encountered. The include statement facilitates the administration of configuration files by permitting the reading or writing of some things but not others. For example, the statement could include private keys that are readable only by the name server.
The key statement defines a shared secret key for use with TSIG (see the section called “TSIG”) or the command channel (see the section called “controls Statement Definition and Usage”).
The key statement can occur at the top level of the configuration file or inside a view statement. Keys defined in top-level key statements can be used in all views. Keys intended for use in a controls statement (see the section called “controls Statement Definition and Usage”) must be defined at the top level.
The key_id, also known as the
key name, is a domain name uniquely identifying the key. It can
be used in a server
statement to cause requests sent to that
server to be signed with this key, or in address match lists to
verify that incoming requests have been signed with a key
matching this name, algorithm, and secret.
The algorithm_id is a string
that specifies a security/authentication algorithm. The only
algorithm currently supported with TSIG authentication is
hmac-md5. The
secret_string is the secret to be
used by the algorithm, and is treated as a base-64 encoded
string.
logging { [ channelchannel_name{ ( filepath name[ versions (number|unlimited) ] [ sizesize spec] | syslogsyslog_facility| stderr | null ); [ severity (critical|error|warning|notice|info|debug[level] |dynamic); ] [ print-categoryyesorno; ] [ print-severityyesorno; ] [ print-timeyesorno; ] }; ] [ categorycategory_name{channel_name; [channel_name ; ... ] }; ] ... };
The logging statement configures a wide variety of logging options for the name server. 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 is no logging statement, the logging configuration will be:
logging {
category default { default_syslog; default_debug; };
category unmatched { null; };
};
In BIND 9, the logging configuration is only established when
the entire configuration file has been parsed. In BIND 8, it was
established as soon as the logging statement
was parsed. When the server is starting up, all logging messages
regarding syntax errors in the configuration file go to the default
channels, or to standard error if the "-g" option
was specified.
All log output goes to one or more channels; you can make as many of them as you want.
Every channel definition must include a destination clause that says whether messages selected for the channel go to a file, to a particular syslog facility, to the standard error stream, or are discarded. It can optionally also limit the message severity level that will be accepted by the channel (the default is info), and whether to include a named-generated time stamp, the category name and/or severity level (the default is not to include any).
The null destination clause causes all messages sent to the channel to be discarded; in that case, other options for the channel are meaningless.
The file destination clause directs the channel to a disk file. It 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.
If you use the versions log file option, then
named will retain that 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
lamers.log.2, lamers.log.0 is renamed
to lamers.log.1, and lamers.log is
renamed to lamers.log.0.
You can say versions unlimited to not limit
the number of versions.
If a size option is associated with the log file,
then renaming is only done when the file being opened exceeds the
indicated size. No backup versions are kept by default; any existing
log file is simply appended.
The size option for files is used to limit log growth. If the file ever exceeds the size, then named will stop writing to the file unless it has a versions option associated with it. If backup versions are kept, the files are rolled as described above and a new one begun. If there is no versions option, no more data will be written to the log until some out-of-band mechanism removes or truncates the log to less than the maximum size. The default behavior is not to limit the size of the file.
Example usage of the size and versions options:
channel an_example_channel {
file "example.log" versions 3 size 20m;
print-time yes;
print-category yes;
};
The syslog destination clause directs the channel to the system log. Its argument is a syslog facility as described in the syslog man page. Known facilities are kern, user, mail, daemon, auth, syslog, lpr, news, uucp, cron, authpriv, ftp, local0, local1, local2, local3, local4, local5, local6 and local7, however not all facilities are supported on all operating systems. How syslog will handle messages sent to this facility is described in the syslog.conf man page. If you have a system which uses a very old version of syslog 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 info and notice to be dropped. If the situation were reversed, with named writing messages of only warning or higher, then syslogd would print all messages it received from the channel.
The stderr destination clause directs the channel to the server's standard error stream. This is intended for use when the server is running as a foreground process, for example when debugging a configuration.
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 named server
with the -d flag followed by a positive integer,
or by running rndc trace.
The global debug level
can be set to zero, and debugging mode turned off, by running 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 debug 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, severity. Here is an example where all three print- options are on:
28-Feb-2000 15:05:32.863 general: notice: running
There are four predefined channels that are used for named's default logging as follows. How they are used is described in the section called “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 {
stderr; // writes to stderr
severity info; // only send priority info
// and higher
};
channel null {
null; // toss anything sent to
// this channel
};
The default_debug channel has the special
property that it only produces output when the server's debug level is
nonzero. It normally writes to a file named.run
in the server's working directory.
For security reasons, when the "-u"
command line option is used, the named.run file
is created only after named has changed to the
new UID, and any debug output generated while named is
starting up and still running as root is discarded. If you need
to capture this output, you must run the server with the "-g"
option and redirect standard error to a file.
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.
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 default" is used:
category default { default_syslog; default_debug; };
As an example, let's say 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 xfer-out { null; };
category notify { null; };
Following are the available categories and brief descriptions of the types of log information they contain. More categories may be added in future BIND releases.
default |
The default category defines the logging options for those categories where no specific configuration has been defined. |
general |
The catch-all. Many things still aren't classified into categories, and they all end up here. |
database |
Messages relating to the databases used internally by the name server to store zone and cache data. |
security |
Approval and denial of requests. |
config |
Configuration file parsing and processing. |
resolver |
DNS resolution, such as the recursive lookups performed on behalf of clients by a caching name server. |
xfer-in |
Zone transfers the server is receiving. |
xfer-out |
Zone transfers the server is sending. |
notify |
The NOTIFY protocol. |
client |
Processing of client requests. |
unmatched |
Messages that named was unable to determine the class of or for which there was no matching view. A one line summary is also logged to the client category. This category is best sent to a file or stderr, by default it is sent to the null channel. |
network |
Network operations. |
update |
Dynamic updates. |
update-security |
Approval and denial of update requests. |
queries |
Specify where queries should be logged to. At startup, specifing the category queries will also enable query logging unless querylog option has been specified. The query log entry reports the client's IP address and port number. The query name, class and type. It also reports whether the Recursion Desired flag was set (+ if set, - if not set), EDNS was in use (E) or if the query was signed (S).
|
dispatch |
Dispatching of incoming packets to the server modules where they are to be processed. |
dnssec |
DNSSEC and TSIG protocol processing. |
lame-servers |
Lame servers. These are misconfigurations in remote servers, discovered by BIND 9 when trying to query those servers during resolution. |
delegation-only |
Delegation only. Logs queries that have have been forced to NXDOMAIN as the result of a delegation-only zone or a delegation-only in a hint or stub zone declaration. |
This is the grammar of the lwres
statement in the named.conf file:
lwres { [ listen-on {ip_addr[portip_port] ; [ip_addr[portip_port] ; ... ] }; ] [ viewview_name; ] [ search {domain_name; [domain_name; ... ] }; ] [ ndotsnumber; ] };
The lwres statement configures the name server to also act as a lightweight resolver server, see the section called “Running a Resolver Daemon”. There may be be multiple lwres statements configuring lightweight resolver servers with different properties.
The listen-on statement specifies a list of addresses (and ports) that this instance of a lightweight resolver daemon should accept requests on. If no port is specified, port 921 is used. If this statement is omitted, requests will be accepted on 127.0.0.1, port 921.
The view statement binds this instance of a lightweight resolver daemon to a view in the DNS namespace, so that the response will be constructed in the same manner as a normal DNS query matching this view. If this statement is omitted, the default view is used, and if there is no default view, an error is triggered.
The search statement is equivalent to the
search statement in
/etc/resolv.conf. It provides a list of domains
which are appended to relative names in queries.
The ndots statement is equivalent to the
ndots statement in
/etc/resolv.conf. It indicates the minimum
number of dots in a relative domain name that should result in an
exact match lookup before search path elements are appended.
mastersname[portip_port] { (masters_list|ip_addr[portip_port] [keykey] ) ; [...] } ;
masters lists allow for a common set of masters to be easily used by multiple stub and slave zones.
This is the grammar of the options
statement in the named.conf file:
options {
[ version version_string; ]
[ hostname hostname_string; ]
[ server-id server_id_string; ]
[ directory path_name; ]
[ key-directory path_name; ]
[ named-xfer path_name; ]
[ tkey-domain domainname; ]
[ tkey-dhkey key_name key_tag; ]
[ dump-file path_name; ]
[ memstatistics-file path_name; ]
[ pid-file path_name; ]
[ statistics-file path_name; ]
[ zone-statistics yes_or_no; ]
[ auth-nxdomain yes_or_no; ]
[ deallocate-on-exit yes_or_no; ]
[ dialup dialup_option; ]
[ fake-iquery yes_or_no; ]
[ fetch-glue yes_or_no; ]
[ flush-zones-on-shutdown yes_or_no; ]
[ has-old-clients yes_or_no; ]
[ host-statistics yes_or_no; ]
[ host-statistics-max number; ]
[ minimal-responses yes_or_no; ]
[ multiple-cnames yes_or_no; ]
[ notify yes_or_no | explicit; ]
[ recursion yes_or_no; ]
[ rfc2308-type1 yes_or_no; ]
[ use-id-pool yes_or_no; ]
[ maintain-ixfr-base yes_or_no; ]
[ dnssec-enable yes_or_no; ]
[ dnssec-lookaside domain trust-anchor domain; ]
[ dnssec-must-be-secure domain yes_or_no; ]
[ forward ( only | first ); ]
[ forwarders { [ ip_addr [port ip_port] ; ... ] }; ]
[ dual-stack-servers [port ip_port] { ( domain_name [port ip_port] | ip_addr [port ip_port] ) ; ... }; ]
[ check-names ( master | slave | response )( warn | fail | ignore ); ]
[ allow-notify { address_match_list }; ]
[ allow-query { address_match_list }; ]
[ allow-transfer { address_match_list }; ]
[ allow-recursion { address_match_list }; ]
[ allow-update-forwarding { address_match_list }; ]
[ allow-v6-synthesis { address_match_list }; ]
[ blackhole { address_match_list }; ]
[ avoid-v4-udp-ports { port_list }; ]
[ avoid-v6-udp-ports { port_list }; ]
[ listen-on [ port ip_port ] { address_match_list }; ]
[ listen-on-v6 [ port ip_port ] { address_match_list }; ]
[ query-source [ address ( ip_addr | * ) ] [ port ( ip_port | * ) ]; ]
[ query-source-v6 [ address ( ip_addr | * ) ] [ port ( ip_port | * ) ]; ]
[ max-transfer-time-in number; ]
[ max-transfer-time-out number; ]
[ max-transfer-idle-in number; ]
[ max-transfer-idle-out number; ]
[ tcp-clients number; ]
[ recursive-clients number; ]
[ serial-query-rate number; ]
[ serial-queries number; ]
[ tcp-listen-queue number; ]
[ transfer-format ( one-answer | many-answers ); ]
[ transfers-in number; ]
[ transfers-out number; ]
[ transfers-per-ns number; ]
[ transfer-source (ip4_addr | *) [port ip_port] ; ]
[ transfer-source-v6 (ip6_addr | *) [port ip_port] ; ]
[ alt-transfer-source (ip4_addr | *) [port ip_port] ; ]
[ alt-transfer-source-v6 (ip6_addr | *) [port ip_port] ; ]
[ use-alt-transfer-source yes_or_no; ]
[ notify-source (ip4_addr | *) [port ip_port] ; ]
[ notify-source-v6 (ip6_addr | *) [port ip_port] ; ]
[ also-notify { ip_addr [port ip_port] ; [ ip_addr [port ip_port] ; ... ] }; ]
[ max-ixfr-log-size number; ]
[ max-journal-size size_spec; ]
[ coresize size_spec ; ]
[ datasize size_spec ; ]
[ files size_spec ; ]
[ stacksize size_spec ; ]
[ cleaning-interval number; ]
[ heartbeat-interval number; ]
[ interface-interval number; ]
[ statistics-interval number; ]
[ topology { address_match_list }];
[ sortlist { address_match_list }];
[ rrset-order { order_spec ; [ order_spec ; ... ] ] };
[ lame-ttl number; ]
[ max-ncache-ttl number; ]
[ max-cache-ttl number; ]
[ sig-validity-interval number ; ]
[ min-roots number; ]
[ use-ixfr yes_or_no ; ]
[ provide-ixfr yes_or_no; ]
[ request-ixfr yes_or_no; ]
[ treat-cr-as-space yes_or_no ; ]
[ min-refresh-time number ; ]
[ max-refresh-time number ; ]
[ min-retry-time number ; ]
[ max-retry-time number ; ]
[ port ip_port; ]
[ additional-from-auth yes_or_no ; ]
[ additional-from-cache yes_or_no ; ]
[ random-device path_name ; ]
[ max-cache-size size_spec ; ]
[ match-mapped-addresses yes_or_no; ]
[ preferred-glue ( A | AAAA | NONE ); ]
[ edns-udp-size number; ]
[ root-delegation-only [ exclude { namelist } ] ; ]
[ querylog yes_or_no ; ]
[ disable-algorithms domain { algorithm; [ algorithm; ] }; ]
};
The options statement sets up global options to be used by BIND. This statement may appear only once in a configuration file. If there is no options statement, an options block with each option set to its default will be used.
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 (e.g. 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.
When performing dynamic update of secure zones, the directory where the public and private key files should be found, if different than the current working directory. The directory specified must be an absolute path.
This option is obsolete. It was used in BIND 8 to specify the pathname to the named-xfer program. In BIND 9, no separate named-xfer program is needed; its functionality is built into the name server.
The domain appended to the names of all
shared keys generated with TKEY. When a client
requests a TKEY exchange, it may or may not specify
the desired name for the key. If present, the name of the shared
key will be "client specified part" +
"tkey-domain".
Otherwise, the name of the shared key will be "random hex
digits" + "tkey-domain". In most cases,
the domainname should be the server's domain
name.
The Diffie-Hellman key used by the server to generate shared keys with clients using the Diffie-Hellman mode of TKEY. The server must be able to load the public and private keys from files in the working directory. In most cases, the keyname should be the server's host name.
The pathname of the file the server dumps
the database to when instructed to do so with
rndc dumpdb.
If not specified, the default is named_dump.db.
The pathname of the file the server writes memory
usage statistics to on exit. If not specified,
the default is named.memstats.
The pathname of the file the server writes its process ID
in. If not specified, the default is /var/run/named.pid.
The pid-file is used by programs that want to send signals to the running
name server. Specifying pid-file none disables the
use of a PID file — no file will be written and any
existing one will be removed. Note that none
is a keyword, not a file name, and therefore is not enclosed in
double quotes.
The pathname of the file the server appends statistics
to when instructed to do so using rndc stats.
If not specified, the default is named.stats in the
server's current directory. The format of the file is described
in the section called “The Statistics File”
The UDP/TCP port number the server uses for receiving and sending DNS protocol traffic. The default is 53. This option is mainly intended for server testing; a server using a port other than 53 will not be able to communicate with the global DNS.
The source of entropy to be used by the server. Entropy is primarily needed
for DNSSEC operations, such as TKEY transactions and dynamic update of signed
zones. This options specifies the device (or file) from which to read
entropy. If this is a file, operations requiring entropy will fail when the
file has been exhausted. If not specified, the default value is
/dev/random
(or equivalent) when present, and none otherwise. The
random-device option takes effect during
the initial configuration load at server startup time and
is ignored on subsequent reloads.
If specified the listed type (A or AAAA) will be emitted before other glue in the additional section of a query response. The default is not to preference any type (NONE).
Turn on enforcement of delegation-only in TLDs and root zones with an optional exclude list.
Note some TLDs are NOT delegation only (e.g. "DE", "LV", "US" and "MUSEUM").
options {
root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
};
Disable the specified DNSSEC algorithms at and below the specified name. Multiple disable-algorithms statements are allowed. Only the most specific will be applied.
When set dnssec-lookaside provides the validator with an alternate method to validate DNSKEY records at the top of a zone. When a DNSKEY is at or below a domain specified by the deepest dnssec-lookaside, and the normal dnssec validation has left the key untrusted, the trust-anchor will be append to the key name and a DLV record will be looked up to see if it can validate the key. If the DLV record validates a DNSKEY (similarly to the way a DS record does) the DNSKEY RRset is deemed to be trusted.
Specify heirarchies which must / may not be secure (signed and validated).
If yes then named will only accept answers if they
are secure.
If no then normal dnssec validation applies
allowing for insecure answers to be accepted.
The specified domain must be under a trusted-key or
dnssec-lookaside must be active.
If yes, then the AA bit
is always set on NXDOMAIN responses, even if the server is not actually
authoritative. The default is no; this is
a change from BIND 8. If you are using very old DNS software, you
may need to set it to yes.
This option was used in BIND 8 to enable checking for memory leaks on exit. BIND 9 ignores the option and always performs the checks.
If yes, then the
server treats all zones as if they are doing zone transfers across
a dial on demand dialup link, which can be brought up by traffic
originating from this server. This has different effects according
to zone type and concentrates the zone maintenance so that it all
happens in a short interval, once every heartbeat-interval and
hopefully during the one call. It also suppresses some of the normal
zone maintenance traffic. The default is no.
The dialup option may also be specified in the view and zone statements, in which case it overrides the global dialup option.
If the zone is a master zone then the server will send out a NOTIFY request to all the slaves (default). This should trigger the zone serial number check in the slave (providing it supports NOTIFY) allowing the slave to verify the zone while the connection is active. The set of servers to which NOTIFY is sent can be controlled by notify and also-notify.
If the zone is a slave or stub zone, then the server will suppress the regular "zone up to date" (refresh) queries and only perform them when the heartbeat-interval expires in addition to sending NOTIFY requests.
Finer control can be achieved by using
notify which only sends NOTIFY messages,
notify-passive which sends NOTIFY messages and
suppresses the normal refresh queries, refresh
which suppresses normal refresh processing and sends refresh queries
when the heartbeat-interval expires, and
passive which just disables normal refresh
processing.
dialup mode |
normal refresh |
heart-beat refresh |
heart-beat notify |
no (default) |
yes |
no |
no |
yes |
no |
yes |
yes |
notify |
yes |
no |
yes |
refresh |
no |
yes |
no |
passive |
no |
no |
no |
notify-passive |
no |
no |
yes |
Note that normal NOTIFY processing is not affected by dialup.
In BIND 8, this option enabled simulating the obsolete DNS query type IQUERY. BIND 9 never does IQUERY simulation.
This option is obsolete.
In BIND 8, fetch-glue yes
caused the server to attempt to fetch glue resource records it
didn't have when constructing the additional
data section of a response. This is now considered a bad idea
and BIND 9 never does it.
When the nameserver exits due receiving SIGTERM,
flush / do not flush any pending zone writes. The default is
flush-zones-on-shutdown no.
This option was incorrectly implemented
in BIND 8, and is ignored by BIND 9.
To achieve the intended effect
of
has-old-clients yes, specify
the two separate options auth-nxdomain yes
and rfc2308-type1 no instead.
In BIND 8, this enables keeping of statistics for every host that the name server interacts with. Not implemented in BIND 9.
This option is obsolete.
It was used in BIND 8 to determine whether a transaction log was
kept for Incremental Zone Transfer. BIND 9 maintains a transaction
log whenever possible. If you need to disable outgoing incremental zone
transfers, use provide-ixfr no.
If yes, then when generating
responses the server will only add records to the authority and
additional data sections when they are required (e.g. delegations,
negative responses). This may improve the performance of the server.
The default is no.
This option was used in BIND 8 to allow a domain name to have multiple CNAME records in violation of the DNS standards. BIND 9.2 always strictly enforces the CNAME rules both in master files and dynamic updates.
If yes (the default),
DNS NOTIFY messages are sent when a zone the server is authoritative for
changes, see the section called “Notify”. The messages are sent to the
servers listed in the zone's NS records (except the master server identified
in the SOA MNAME field), and to any servers listed in the
also-notify option.
If explicit, notifies are sent only to
servers explicitly listed using also-notify.
If no, no notifies are sent.
The notify option may also be specified in the zone statement, in which case it overrides the options notify statement. It would only be necessary to turn off this option if it caused slaves to crash.
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 off
and the server does not already know the answer, it will return a
referral response. The default is yes.
Note that setting recursion no does not prevent
clients from getting data from the server's cache; it only
prevents new data from being cached as an effect of client queries.
Caching may still occur as an effect the server's internal
operation, such as NOTIFY address lookups.
See also fetch-glue above.
Setting this to yes will
cause the server to send NS records along with the SOA record for negative
answers. The default is no.
Not yet implemented in BIND 9.
This option is obsolete. BIND 9 always allocates query IDs from a pool.
If yes, the server will collect
statistical data on all zones (unless specifically turned off
on a per-zone basis by specifying zone-statistics no
in the zone statement). These statistics may be accessed
using rndc stats, which will dump them to the file listed
in the statistics-file. See also the section called “The Statistics File”.
This option is obsolete. If you need to disable IXFR to a particular server or servers see the information on the provide-ixfr option in the section called “server Statement Definition and Usage”. See also the section called “Incremental Zone Transfers (IXFR)”.
See the description of provide-ixfr in the section called “server Statement Definition and Usage”
See the description of request-ixfr in the section called “server Statement Definition and Usage”
This option was used in BIND 8 to make the server treat carriage return ("\r") characters the same way as a space or tab character, to facilitate loading of zone files on a UNIX system that were generated on an NT or DOS machine. In BIND 9, both UNIX "\n" and NT/DOS "\r\n" newlines are always accepted, and the option is ignored.
These options control the behavior of an authoritative server when answering queries which have additional data, or when following CNAME and DNAME chains.
When both of these options are set to yes
(the default) and a
query is being answered from authoritative data (a zone
configured into the server), the additional data section of the
reply will be filled in using data from other authoritative zones
and from the cache. In some situations this is undesirable, such
as when there is concern over the correctness of the cache, or
in servers where slave zones may be added and modified by
untrusted third parties. Also, avoiding
the search for this additional data will speed up server operations
at the possible expense of additional queries to resolve what would
otherwise be provided in the additional section.
For example, if a query asks for an MX record for host foo.example.com,
and the record found is "MX 10 mail.example.net", normally the address
records (A and AAAA) for mail.example.net will be provided as well,
if known, even though they are not in the example.com zone.
Setting these options to no disables this behavior and makes
the server only search for additional data in the zone it answers from.
These options are intended for use in authoritative-only servers, or in authoritative-only views. Attempts to set them to no without also specifying recursion no will cause the server to ignore the options and log a warning message.
Specifying additional-from-cache no actually disables the use of the cache not only for additional data lookups but also when looking up the answer. This is usually the desired behavior in an authoritative-only server where the correctness of the cached data is an issue.
When a name server is non-recursively queried for a name that is not below the apex of any served zone, it normally answers with an "upwards referral" to the root servers or the servers of some other known parent of the query name. Since the data in an upwards referral comes from the cache, the server will not be able to provide upwards referrals when additional-from-cache no has been specified. Instead, it will respond to such queries with REFUSED. This should not cause any problems since upwards referrals are not required for the resolution process.
If yes, then an
IPv4-mapped IPv6 address will match any address match
list entries that match the corresponding IPv4 address.
Enabling this option is sometimes useful on IPv6-enabled Linux
systems, to work around a kernel quirk that causes IPv4
TCP connections such as zone transfers to be accepted
on an IPv6 socket using mapped addresses, causing
address match lists designed for IPv4 to fail to match.
The use of this option for any other purpose is discouraged.
When 'yes' and the server loads a new version of a master zone from its zone file or receives a new version of a slave file by a non-incremental zone transfer, it will compare the new version to the previous one and calculate a set of differences. The differences are then logged in the zone's journal file such that the changes can be transmitted to downstream slaves as an incremental zone transfer.
By allowing incremental zone transfers to be used for non-dynamic zones, this option saves bandwidth at the expense of increased CPU and memory consumption at the master. In particular, if the new version of a zone is completely different from the previous one, the set of differences will be of a size comparable to the combined size of the old and new zone version, and the server will need to temporarily allocate memory to hold this complete difference set.
This should be set when you have multiple masters for a zone and the
addresses refer to different machines. If 'yes' named will not log
when the serial number on the master is less than what named currently
has. The default is no.
Enable DNSSEC support in named. Unless set to yes
named behaves as if it does not support DNSSEC.
The default is no.
Specify whether query logging should be started when named start. If querylog is not specified then the query logging is determined by the presence of the logging category queries.
This option is used to restrict the character set and syntax of certain domain names in master files and/or DNS responses received from the network. The default varies according to usage area. For master zones the default is fail. For slave zones the default is warn. For answer received from the network (response) the default is ignore.
The rules for legal hostnames / mail domains are derived from RFC 952 and RFC 821 as modified by RFC 1123.
check-names applies to the owner names of A, AAA and MX records. It also applies to the domain names in the RDATA of NS, SOA and MX records. It also applies to the RDATA of PTR records where the owner name indicated that it is a reverse lookup of a hostname (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, IP6.INT).
The forwarding facility can be used to create a large site-wide cache on a few servers, reducing traffic over links to external name servers. 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.
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.
Specifies the IP addresses to be used for forwarding. The default is the empty list (no forwarding).
Forwarding can also be configured on a per-domain basis, allowing for the global forwarding options to be overridden in a variety of ways. You can set particular domains to use different forwarders, or have a different forward only/first behavior, or not forward at all, see the section called “zone Statement Grammar”.
Dual-stack servers are used as servers of last resort to work around problems in reachability due the lack of support for either IPv4 or IPv6 on the host machine.
Specifies host names / addresses of machines with access to both IPv4 and IPv6 transports. If a hostname is used the server must be able to resolve the name using only the transport it has. If the machine is dual stacked then the dual-stack-servers have no effect unless access to a transport has been disabled on the command line (e.g. named -4).
Access to the server can be restricted based on the IP address of the requesting system. See the section called “Address Match Lists” for details on how to specify IP address lists.
Specifies which hosts are allowed to notify this server, a slave, of zone changes in addition to the zone masters. allow-notify may also be specified in the zone statement, in which case it overrides the options allow-notify statement. It is only meaningful for a slave zone. If not specified, the default is to process notify messages only from a zone's master.
Specifies which hosts are allowed to ask ordinary DNS 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.
Specifies which hosts are allowed to make recursive queries through this server. If not specified, the default is to allow recursive queries from all hosts. Note that disallowing recursive queries for a host does not prevent the host from retrieving data that is already in the server's cache.
Specifies which hosts are allowed to
submit Dynamic DNS updates to slave zones to be forwarded to the
master. The default is { none; }, which
means that no update forwarding will be performed. To enable
update forwarding, specify
allow-update-forwarding { any; };.
Specifying values other than { none; } or
{ any; } is usually counterproductive, since
the responsibility for update access control should rest with the
master server, not the slaves.
Note that enabling the update forwarding feature on a slave server may expose master servers relying on insecure IP address based access control to attacks; see the section called “Dynamic Update Security” for more details.
This option was introduced for the smooth transition from AAAA to A6 and from "nibble labels" to binary labels. However, since both A6 and binary labels were then deprecated, this option was also deprecated. It is now ignored with some warning messages.
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 to all hosts.
Specifies a list of addresses that the
server will not accept queries from or use to resolve a query. Queries
from these addresses will not be responded to. The default is none.
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; };
will enable the name server on port 53 for the IP address 5.6.7.8, and on port 1234 of an address on the machine in net 1.2 that is not 1.2.3.4.
If no listen-on is specified, the server will listen on port 53 on all interfaces.
The listen-on-v6 option is used to specify the interfaces and the ports on which the server will listen for incoming queries sent using IPv6.
When
{ any; }
is specified
as the address_match_list for the
listen-on-v6 option,
the server does not bind a separate socket to each IPv6 interface
address as it does for IPv4 if the operating system has enough API
support for IPv6 (specifically if it conforms to RFC 3493 and RFC 3542).
Instead, it listens on the IPv6 wildcard address.
If the system only has incomplete API support for IPv6, however,
the behavior is the same as that for IPv4.
A list of particular IPv6 addresses can also be specified, in which case the server listens on a separate socket for each specified address, regardless of whether the desired API is supported by the system.
Multiple listen-on-v6 options can be used. For example,
listen-on-v6 { any; };
listen-on-v6 port 1234 { !2001:db8::/32; any; };
will enable the name server on port 53 for any IPv6 addresses (with a single wildcard socket), and on port 1234 of IPv6 addresses that is not in the prefix 2001:db8::/32 (with separate sockets for each matched address.)
To make the server not listen on any IPv6 address, use
listen-on-v6 { none; };
If no listen-on-v6 option is specified, the server will not listen on any IPv6 address.
If the server doesn't know the answer to a question, it will query other name servers. query-source specifies the address and port used for such queries. For queries sent over IPv6, there is a separate query-source-v6 option. 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, avoid-v4-udp-ports and avoid-v6-udp-ports can be used to prevent named from selecting certain ports. The defaults are
query-source address * port *; query-source-v6 address * port *;
The address specified in the query-source option is used for both UDP and TCP queries, but the port applies only to UDP queries. TCP queries always use a random unprivileged port.
See also transfer-source and notify-source.
BIND has mechanisms in place to facilitate zone transfers and set limits on the amount of load that transfers place on the system. The following options apply to zone transfers.
Defines a global list of IP addresses of name servers that are also sent NOTIFY messages whenever a fresh copy of the zone is loaded, in addition to the servers listed in the zone's NS records. This helps to ensure that copies of the zones will quickly converge on stealth servers. If an also-notify list is given in a zone statement, it will override the options also-notify statement. When a zone notify statement is set to no, the IP addresses in the global also-notify list will not be sent NOTIFY messages for that zone. The default is the empty list (no global notification list).
Inbound zone transfers running longer than this many minutes will be terminated. The default is 120 minutes (2 hours). The maximum value is 28 days (40320 minutes).
Inbound zone transfers making no progress in this many minutes will be terminated. The default is 60 minutes (1 hour). The maximum value is 28 days (40320 minutes).
Outbound zone transfers running longer than this many minutes will be terminated. The default is 120 minutes (2 hours). The maximum value is 28 days (40320 minutes).
Outbound zone transfers making no progress in this many minutes will be terminated. The default is 60 minutes (1 hour). The maximum value is 28 days (40320 minutes).
Slave servers will periodically query master servers to find out if zone serial numbers have changed. Each such query uses a minute amount of the slave server's network bandwidth. To limit the amount of bandwidth used, BIND 9 limits the rate at which queries are sent. The value of the serial-query-rate option, an integer, is the maximum number of queries sent per second. The default is 20.
In BIND 8, the serial-queries option set the maximum number of concurrent serial number queries allowed to be outstanding at any given time. BIND 9 does not limit the number of outstanding serial queries and ignores the serial-queries option. Instead, it limits the rate at which the queries are sent as defined using the serial-query-rate option.
Zone transfers can be sent using two different formats, one-answer and many-answers. The transfer-format option is used on the master server to determine which format it sends. 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 supported by relatively new slave servers, such as BIND 9, BIND 8.x and patched versions of BIND 4.9.5. The default is many-answers. transfer-format may be overridden on a per-server basis by using the server statement.
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.
The maximum number of outbound zone transfers
that can be running concurrently. Zone transfer requests in excess
of the limit will be refused. The default value is 10.
The maximum number of inbound zone transfers
that can be concurrently transferring from a given remote name server.
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 name server. transfers-per-ns may
be overridden on a per-server basis by using the transfers phrase
of the server statement.
transfer-source determines which local address will be bound to IPv4 TCP connections used to fetch zones transferred inbound by the server. It also determines the source IPv4 address, and optionally the UDP port, used for the refresh queries and forwarded dynamic updates. If not set, it defaults to a system controlled value which will usually be the address of the interface "closest to" the remote end. This address must appear in the remote end's allow-transfer option for the zone being transferred, if one is specified. This statement sets the transfer-source for all zones, but can be overridden on a per-view or per-zone basis by including a transfer-source statement within the view or zone block in the configuration file.
The same as transfer-source, except zone transfers are performed using IPv6.
An alternate transfer source if the one listed in transfer-source fails and use-alt-transfer-source is set.
An alternate transfer source if the one listed in transfer-source-v6 fails and use-alt-transfer-source is set.
Use the alternate transfer sources or not. If views are specified this defaults to no otherwise it defaults to yes (for BIND 8 compatibility).
notify-source determines which local source address, and optionally UDP port, will be used to send NOTIFY messages. This address must appear in the slave server's masters zone clause or in an allow-notify clause. This statement sets the notify-source for all zones, but can be overridden on a per-zone / per-view basis by including a notify-source statement within the zone or view block in the configuration file.
Like notify-source, but applies to notify messages sent to IPv6 addresses.
avoid-v4-udp-ports and avoid-v6-udp-ports specify a list of IPv4 and IPv6 UDP ports that will not be used as system assigned source ports for UDP sockets. These lists prevent named from choosing as its random source port a port that is blocked by your firewall. If a query went out with such a source port, the answer would not get by the firewall and the name server would have to query again.
The server's usage of many system resources can be limited. 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 the description of size_spec in the section called “Configuration File Elements”.
The following options set operating system resource limits for the name server process. Some operating systems don't support some or any of the limits. On such systems, a warning will be issued if the unsupported limit is used.
The maximum size of a core dump. The default
is default.
The maximum amount of data memory the server
may use. The default is default.
This is a hard limit on server memory usage.
If the server attempts to allocate memory in excess of this
limit, the allocation will fail, which may in turn leave
the server unable to perform DNS service. Therefore,
this option is rarely useful as a way of limiting the
amount of memory used by the server, but it can b