named(1M) named(1M)
NAME [Toc] [Back]
named - Internet domain name server
SYNOPSIS [Toc] [Back]
named [-c config_file] [-d debuglevel] [-f] [-g] [-n no_of_cpus]
[-p port_number] [-t directory] [-u user_id] [-v]
DESCRIPTION [Toc] [Back]
named is the Internet domain name server. See RFC 1033, RFC 1034, and
RFC 1035 for more information on the Domain Name System (DNS).
Without any arguments, named reads the default configuration file
/etc/named.conf, reads any initial data, and listens for queries.
named requires superuser privileges to execute.
Options [Toc] [Back]
-c config_file
Use a config_file other than /etc/named.conf.
-d debuglevel
Print debugging information. A number after the d
determines the level of messages printed. If negative,
debuglevel is set to ``1''.
NOTE: The new debugging framework is considerably more
sophisticated than it was in older versions of named.
The configuration file's logging statement allows for
multiple, distinct levels of debugging for each of a
large set of categories of events (such as queries,
transfers in or out, etc.).
-f Run this process in the foreground; don't fork(2) and
daemonize. (The default is to daemonize.)
-g Specifies to log all the logging to stderr while named
is running in foreground.
-n no_of_cpus
This option can be used to create worker threads equal
to no_of_cpus to take advantage of multiple CPUs. If
no option is given, named will try to determine the
number of CPUs present and create one thread per CPU.
If named is unable to determine the number of CPUs, a
single worker thread is created.
-p port_number
Use a different port number.
NOTE: Previously, the syntax: " -p port#[/localport#] "
was supported; the first port was that used when
contacting remote servers, and the second one was the
service port bound by the local instance of named. The
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current usage is equivalent to the old usage without
the localport# specified; this functionality can be
specified with the listen-on clause of the
configuration file's options statement.
-t directory
Specifies the working directory the server should run.
directory clause of the configuration file's options
statement overrides any value specified on the command
line. The default working directory is the current
directory (.).
-u user_id
Specifies the user the server should run as after it
initializes. The value specified may be either a
username or a numeric user id.
-v Report version number and exit.
Any additional argument is taken as the name of the configuration
file. The configuration file contains information about where the
name server gets its initial data. If multiple configuration files
are specified, only the last is used. Lines in the configuration file
cannot be continued on subsequent lines. The following is a small
example:
//
/* configuration file for name server */
#
options {
directory "/usr/local/domain";
forwarders {
10.0.0.78;
10.2.0.78;
};
};
key rndc_key {
algorithm "hmac-md5";
secret "c3Ryb25nIGVub3VnaCBmb3IgYSBtYW4gYnV0IG1hZGUgZm9yIGEgd29tYW4K";
};
controls {
inet 127.0.0.1 allow { 127.0.0.1; } keys { rndc_key; };
};
zone "." {
type hint;
file "db.cache";
};
zone "berkeley.edu" {
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type master;
file "db.berkeley";
};
zone "32.128.in-addr.arpa" {
type master;
file "db.128.32";
};
zone "cc.berkeley.edu" {
type slave;
file "db.cc";
masters {
128.32.137.8;
};
};
The directory statement changes the working directory of the server to
the directory specified. The working directory specified is relative
to the new root directory if set by the -t option. This can be
important for the correct processing of $INCLUDE files (described
later) in primary server's master files.
Files referenced in the configuration file contain data in the master
file format described in RFC 1035.
The key statement names a key with its string argument. The string
has to be a valid domain name. However, this need not be
hierarchical; thus, a string "rndc_key" is a valid name.
The key statement has two clauses: algorithm and secret. The
configuration parser will accept any string as the argument to
algorithm. However, only the string "hmac-md5" is supported for
accepting control messages from the utility, rndc. See rndc(1) and
rndc.conf(4). The secret is a base-64 encoded string, typically
generated with dnssec-keygen.
The controls statement is used to configure the name server to accept
connections from the utility, rndc which controls the name server.
The key specified in this statement should match the one set in the
rndc configuration file, rndc.conf.
The forwarders line specifies the addresses of sitewide servers that
will accept recursive queries from other servers. If the
configuration file specifies one or more forwarders, then the server
will send all queries for data not in the cache or in its
authoritative data to the forwarders first. Each forwarder will be
asked in turn until an answer is returned or the list is exhausted.
If no answer is forthcoming from a forwarder, the server will continue
as it would have without the forwarders line unless it is in
forward-only mode. The forwarding facility is useful to cause a large
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sitewide cache to be generated on a master, and to reduce traffic over
links to outside servers.
The noforward line specifies that the DNS server will not forward any
request for something in or below the listed domains, even if the
forwarders directive exists.
A server can access information from servers in other domains given a
list of root name servers and their addresses. The zone "." line
specifies that data in db.cache is to be placed in the backup cache.
Its use is to prime the server with the locations of root domain
servers. This information is used to find the current root servers
and their addresses. The current root server information is placed in
the operating cache. Data for the root name servers in the backup
cache are never discarded.
The zone "berkeley.edu" line states that the master file db.berkeley
contains authoritative data for the berkeley.edu zone. A server
authoritative for a zone has the most accurate information for the
zone. All domain names are relative to the origin, in this case,
berkeley.edu (see below for a more detailed description).
The zone "32.128.in-addr.arpa" line states that the file db.128.32
contains authoritative data for the domain 32.128.in-addr.arpa. This
domain is used to translate addresses in network 128.32 to hostnames.
The zone "cc.berkeley.edu" line specifies that all authoritative data
in the cc.berkeley.edu zone is to be transferred from the name server
at Internet address 128.32.137.8 and will be saved in the backup file
db.cc. Up to 10 addresses can be listed on this line. If a transfer
fails, it will try the next address in the list. The secondary copy
is also authoritative for the specified domain. The first nonInternet
address on this line will be taken as a filename in which to
backup the transferred zone. The name server will load the zone from
this backup file (if it exists) when it boots, providing a complete
copy, even if the master servers are unreachable. Whenever a new copy
of the domain is received from one of the master servers, this file is
updated. If no file name is given, a temporary file will be used and
will be deleted after each successful zone transfer. This is not
recommended because it causes a needless waste of bandwidth.
IPv6 Options [Toc] [Back]
listen-on-v6 This option will specify the ports on which the
server will listen for incoming queries sent using
IPv6. In this option, only two values are
supported: any and none. If this option is not
specified in the named configuration file
(named.conf), named will not listen on any IPv6
interfaces.
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Examples, using any:
listen-on-v6 port 80 {any;};
listen-on-v6 port 1234 {any;};
Example, using none, to stop the server from
listening to IPv6 addresses:
listen-on-v6 {none;};
NOTE: The hosts_to_named configuration file
migration script does not add the listen-on-v6
option to the named.conf file on dual stack
machine. In order to enable DNS services to
listen on IPv6 interfaces, this entry needs to be
added manually.
query-source-v6 This option will specify the server with IPv6
address, which is to be contacted for the answer
to a query from an IPv6 source.
Example:
query-source-v6 address c000:1::a35 port 5000
transfer-source-v6 This option is similar to the transfer-source
option, but is meant for zone transfers using
IPv6. This works in an identical fashion for both
Options statement grammar and Zone statement
grammar.
Master File Format [Toc] [Back]
The master file consists of control information and a list of resource
records for objects in the zone of the forms:
$INCLUDE filename opt_domain
$ORIGIN domain
domain opt_ttl opt_class type resource_record_data
where:
domain is . for root, @ for the current origin, or a
standard domain name. If domain is a standard
domain name that does not end with ``.'', the
current origin is appended to the domain. Domain
names ending with ``.'' are unmodified.
opt_domain This field is used to define an origin for the
data in an included file. It is equivalent to
placing an $ORIGIN statement before the first line
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of the included file. The field is optional.
Neither the opt_domain field nor $ORIGIN
statements in the included file modify the current
origin for this file.
opt_ttl An optional integer number for the time-to-live
field. It defaults to zero, meaning the minimum
value specified in the SOA record for the zone.
opt_class The object address type; currently only one type
is supported, IN, for objects connected to the
DARPA Internet.
type This field contains one of the following tokens;
the data expected in the resource_record_data
field is in parentheses:
A a host address (dotted-quad IP address)
NS an authoritative name server (domain)
MX a mail exchanger (domain), preceded by a
preference value (0..32767), with lower
numeric values representing higher logical
preferences.
CNAME the canonical name for an alias (domain)
SOA marks the start of a zone of authority
(domain of originating host, domain
address of maintainer, a serial number and
the following parameters in seconds:
refresh, retry, expire and minimum TTL
(see RFC 883)).
NULL a null resource record (no format or data)
RP a Responsible Person for some domain name
(mailbox, TXT-referral)
PTR a domain name pointer (domain)
HINFO host information (cpu_type OS_type)
TXT text data (string)
WKS a well known service description (IP
address followed by a list of services)
Resource records normally end at the end of a line, but may be
continued across lines between opening and closing parentheses.
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Comments are introduced by semicolons and continue to the end of the
line.
NOTE: All the db files have to start with a $TTL value. There are
other resource record types not shown here. You should consult the
BIND Operations Guide (``BOG'') for the complete list. Some resource
record types may have been standardized in newer RFCs but not yet
implemented in this version of BIND.
SOA Record Format [Toc] [Back]
Each master zone file should begin with an SOA record for the zone.
An example SOA record is as follows:
@ IN SOA ucbvax.Berkeley.EDU. rwh.ucbvax.Berkeley.EDU. (
1989020501 ; serial
10800 ; refresh
3600 ; retry
3600000 ; expire
86400 ) ; minimum
The SOA specifies a serial number, which should be changed each time
the master file is changed. Note that, it is not advisable to give
the serial number as a dotted number, since the translation to normal
integers is via concatenation rather than multiplication and addition.
You can spell out the year, month, day of month, and 0..99 version
number and still fit inside the unsigned 32-bit size of this field.
(It's true that we will have to rethink this strategy in the year
4294.)
Secondary servers check the serial number at intervals specified by
the refresh time in seconds; if the serial number changes, a zone
transfer will be done to load the new data. If a master server cannot
be contacted when a refresh is due, the retry time specifies the
interval at which refreshes should be attempted. If a master server
cannot be contacted within the interval given by the expire time, all
data from the zone is discarded by secondary servers. The minimum
value is the time-to-live (``TTL'') used by records in the file with
no explicit time-to-live value.
NOTE: The boot file directives domain and suffixes have been obsoleted
by a more useful, resolver-based implementation of suffixing for
partially-qualified domain names. The prior mechanisms could fail
under a number of situations, especially when then local name server
did not have complete information.
The following signals have the specified effect when sent to the
server process using the kill(1) command:
SIGHUP Causes server to read named.conf and reload
database.
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SIGINT & SIGTERM
Signals can be used to gracefully shut down the
server.
Sending any other signals to the name server will have undefined
outcome.
sig_named(1M) can also be used for sending signals to the server
process.
DIAGNOSTICS [Toc] [Back]
Any errors encountered by named in the configuration file, master
files, or in normal operation are logged with syslog and in the debug
file, ./named.run, if debugging is on and named will quit.
AUTHOR [Toc] [Back]
named was developed by the University of California, Berkeley.
FILES [Toc] [Back]
/etc/named.conf name server configuration file
/var/run/named.pid process ID
./named.run debug output
SEE ALSO [Toc] [Back]
dnssec-keygen(1), dnssec-makekeyset(1), dnssec-signkey(1), dnssecsignzone(1), host(1), kill(1), nsupdate(1), rndc(1),
hosts_to_named(1M), lwresd(1M), signal(2), gethostent(3N),
rndc.conf(4), hostname(5).
RFC 882, RFC 883, RFC 973, RFC 974, RFC 1032, RFC 1033, RFC 1034, RFC
1035, RFC 1123.
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