options Statement
options {
[ directory path_name; ]
[ named-xfer path_name; ]
[ dump-file path_name; ]
[ pid-file path_name; ]
[ statistics-file path_name; ]
[ auth-nxdomain yes_or_no; ]
[ fake-iquery yes_or_no; ]
[ fetch-glue 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 ; ]
[ clean-interval number; ]
[ interface-interval number; ]
[ statistics-interval number; ]
[ topology { address_match_list }; ]
};
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.
directory
named-xfer
dump-file
SIGINT signal (ndc dumpdb). If not
specified, the default is "named_dump.db".
pid-file
statistics-file
SIGILL signal (ndc stats). If not
specified, the default is "named.stats".
auth-nxdomain
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.
fake-iquery
yes, the server will simulate the obsolete DNS query type
IQUERY. The default is no.
fetch-glue
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).
multiple-cnames
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
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
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 above.
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
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
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
warn
fail
The server can check names 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
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
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.
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.
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 *;
Note: query-source currently applies only to UDP queries;
TCP queries always use a wildcard IP address and a random unprivileged
port.
Zone Transfers
max-transfer-time-in
named-xfer processes) running
longer than this many minutes will be terminated. The default is 120
minutes (2 hours).
transfer-format
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
transfers-in may speed up the convergence of slave zones,
but it also may increase the load on the local system.
transfers-out
transfers-per-ns
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.
The server's usage of many system resources can be limited. Some operating systems don't support some of the limits and a warning will be generated if an unsupported limit is set in the configuration file.
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
coresize
default.
datasize
default.
files
unlimited.
stacksize
default.
clean-interval
clean-interval minutes. The default is 60 minutes. If set
to 0, no periodic cleaning will occur.
interface-interval
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
statistics-interval
minutes. The default is 60. If set to 0, no statistics will be logged.
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; };
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