dig — DNS lookup utility
dig
[@server]
[-b
]
[address
-c
]
[class
-f
]
[filename
-k
]
[filename
-m
]
[-p
]
[port#
-q
]
[name
-t
]
[type
-v
]
[-x
]
[addr
-y
]
[
[[hmac:]name:key
-4
]
| [-6
]
]
[name]
[type]
[class]
[queryopt...]
dig
[-h
]
dig
[global-queryopt...]
[query...]
dig is a flexible tool for interrogating DNS name servers. It performs DNS lookups and displays the answers that are returned from the name server(s) that were queried. Most DNS administrators use dig to troubleshoot DNS problems because of its flexibility, ease of use and clarity of output. Other lookup tools tend to have less functionality than dig.
Although dig is normally used with
command-line
arguments, it also has a batch mode of operation for reading lookup
requests from a file. A brief summary of its command-line arguments
and options is printed when the -h
option is given.
Unlike earlier versions, the BIND 9 implementation of
dig allows multiple lookups to be issued
from the
command line.
Unless it is told to query a specific name server,
dig will try each of the servers listed in
/etc/resolv.conf
. If no usable server addresses
are found, dig will send the query to the local
host.
When no command line arguments or options are given, dig will perform an NS query for "." (the root).
It is possible to set per-user defaults for dig via
${HOME}/.digrc
. This file is read and any
options in it are applied before the command line arguments.
The -r
option disables this feature, for
scripts that need predictable behaviour.
The IN and CH class names overlap with the IN and CH top level
domain names. Either use the -t
and
-c
options to specify the type and class,
use the -q
the specify the domain name, or
use "IN." and "CH." when looking up these top level domains.
A typical invocation of dig looks like:
dig @server name type
where:
server
is the name or IP address of the name server to query. This
can be an IPv4 address in dotted-decimal notation or an IPv6
address in colon-delimited notation. When the supplied
server
argument is a hostname,
dig resolves that name before querying
that name server.
If no server
argument is
provided, dig consults
/etc/resolv.conf
; if an
address is found there, it queries the name server at
that address. If either of the -4
or
-6
options are in use, then
only addresses for the corresponding transport
will be tried. If no usable addresses are found,
dig will send the query to the
local host. The reply from the name server that
responds is displayed.
name
is the name of the resource record that is to be looked up.
type
indicates what type of query is required —
ANY, A, MX, SIG, etc.
type
can be any valid query
type. If no
type
argument is supplied,
dig will perform a lookup for an
A record.
Use IPv4 only.
Use IPv6 only.
address[#port]
Set the source IP address of the query.
The address
must be a valid address on
one of the host's network interfaces, or "0.0.0.0" or "::". An
optional port may be specified by appending "#<port>"
class
Set the query class. The
default class
is IN; other classes
are HS for Hesiod records or CH for Chaosnet records.
file
Batch mode: dig reads a list of lookup
requests to process from the
given file
. Each line in the file
should be organized in the same way they would be
presented as queries to
dig using the command-line interface.
Do reverse IPv6 lookups using the obsolete RFC 1886 IP6.INT domain, which is no longer in use. Obsolete bit string label queries (RFC 2874) are not attempted.
keyfile
Sign queries using TSIG using a key read from the given file.
Key files can be generated using
tsig-keygen(8)
.
When using TSIG authentication with dig,
the name server that is queried needs to know the key and
algorithm that is being used. In BIND, this is done by
providing appropriate key
and server statements in
named.conf
.
Enable memory usage debugging.
port
Send the query to a non-standard port on the server, instead of the default port 53. This option would be used to test a name server that has been configured to listen for queries on a non-standard port number.
name
The domain name to query. This is useful to distinguish
the name
from other arguments.
Do not read options from ${HOME}/.digrc
.
This is useful for scripts that need predictable behaviour.
type
The resource record type to query. It can be any valid query
type. If it is a resource record type supported in BIND 9, it
can be given by the type mnemonic (such as "NS" or "AAAA").
The default query type is "A", unless the -x
option is supplied to indicate a reverse lookup. A zone
transfer can be requested by specifying a type of AXFR. When
an incremental zone transfer (IXFR) is required, set the
type
to ixfr=N
.
The incremental zone transfer will contain the changes
made to the zone since the serial number in the zone's SOA
record was
N
.
All resource record types can be expressed as "TYPEnn", where "nn" is the number of the type. If the resource record type is not supported in BIND 9, the result will be displayed as described in RFC 3597.
Print query times in microseconds instead of milliseconds.
Print the version number and exit.
addr
Simplified reverse lookups, for mapping addresses to
names. The addr
is an IPv4 address
in dotted-decimal notation, or a colon-delimited IPv6
address. When the -x
is used, there is no
need to provide
the name
, class
and type
arguments. dig automatically performs a
lookup for a name like
94.2.0.192.in-addr.arpa
and sets the
query type and class to PTR and IN respectively. IPv6
addresses are looked up using nibble format under the
IP6.ARPA domain (but see also the -i
option).
[hmac:]keyname:secret
Sign queries using TSIG with the given authentication key.
keyname
is the name of the key, and
secret
is the base64 encoded shared secret.
hmac
is the name of the key algorithm;
valid choices are hmac-md5
,
hmac-sha1
, hmac-sha224
,
hmac-sha256
, hmac-sha384
, or
hmac-sha512
. If hmac
is not specified, the default is hmac-md5
or if MD5 was disabled hmac-sha256
.
NOTE: You should use the -k
option and
avoid the -y
option, because
with -y
the shared secret is supplied as
a command line argument in clear text. This may be visible
in the output from
ps(1)
or in a history file maintained by the user's shell.
dig provides a number of query options which affect the way in which lookups are made and the results displayed. Some of these set or reset flag bits in the query header, some determine which sections of the answer get printed, and others determine the timeout and retry strategies.
Each query option is identified by a keyword preceded by a plus sign
(+
). Some keywords set or reset an
option. These may be preceded
by the string no
to negate the meaning of
that keyword. Other
keywords assign values to options like the timeout interval. They
have the form +keyword=value
.
Keywords may be abbreviated, provided the abbreviation is
unambiguous; for example, +cd
is equivalent
to +cdflag
.
The query options are:
+[no]aaflag
A synonym for +[no]aaonly
.
+[no]aaonly
Sets the "aa" flag in the query.
+[no]additional
Display [do not display] the additional section of a reply. The default is to display it.
+[no]adflag
Set [do not set] the AD (authentic data) bit in the query. This requests the server to return whether all of the answer and authority sections have all been validated as secure according to the security policy of the server. AD=1 indicates that all records have been validated as secure and the answer is not from a OPT-OUT range. AD=0 indicate that some part of the answer was insecure or not validated. This bit is set by default.
+[no]all
Set or clear all display flags.
+[no]answer
Display [do not display] the answer section of a reply. The default is to display it.
+[no]authority
Display [do not display] the authority section of a reply. The default is to display it.
+[no]badcookie
Retry lookup with the new server cookie if a BADCOOKIE response is received.
+[no]besteffort
Attempt to display the contents of messages which are malformed. The default is to not display malformed answers.
+bufsize=B
Set the UDP message buffer size advertised using EDNS0
to B
bytes. The maximum and
minimum sizes of this buffer are 65535 and 0 respectively.
Values outside this range are rounded up or down
appropriately. Values other than zero will cause a
EDNS query to be sent.
+[no]cdflag
Set [do not set] the CD (checking disabled) bit in the query. This requests the server to not perform DNSSEC validation of responses.
+[no]class
Display [do not display] the CLASS when printing the record.
+[no]cmd
Toggles the printing of the initial comment in the output identifying the version of dig and the query options that have been applied. This comment is printed by default.
+[no]comments
Toggle the display of comment lines in the output. The default is to print comments.
+[no]cookie[=####]
Send a COOKIE EDNS option, with optional
value. Replaying a COOKIE from a previous response will
allow the server to identify a previous client. The
default is +cookie
.
+cookie is also set when +trace is set to better emulate the default queries from a nameserver.
+[no]crypto
Toggle the display of cryptographic fields in DNSSEC records. The contents of these field are unnecessary to debug most DNSSEC validation failures and removing them makes it easier to see the common failures. The default is to display the fields. When omitted they are replaced by the string "[omitted]" or in the DNSKEY case the key id is displayed as the replacement, e.g. "[ key id = value ]".
+[no]defname
Deprecated, treated as a synonym for
+[no]search
+[no]dnssec
Requests DNSSEC records be sent by setting the DNSSEC OK bit (DO) in the OPT record in the additional section of the query.
+domain=somename
Set the search list to contain the single domain
somename
, as if specified in
a domain directive in
/etc/resolv.conf
, and enable
search list processing as if the
+search
option were given.
+dscp=value
Set the DSCP code point to be used when sending the query. Valid DSCP code points are in the range [0..63]. By default no code point is explicitly set.
+[no]edns[=#]
Specify the EDNS version to query with. Valid values
are 0 to 255. Setting the EDNS version will cause
a EDNS query to be sent. +noedns
clears the remembered EDNS version. EDNS is set to
0 by default.
+[no]ednsflags[=#]
Set the must-be-zero EDNS flags bits (Z bits) to the specified value. Decimal, hex and octal encodings are accepted. Setting a named flag (e.g. DO) will silently be ignored. By default, no Z bits are set.
+[no]ednsnegotiation
Enable / disable EDNS version negotiation. By default EDNS version negotiation is enabled.
+[no]ednsopt[=code[:value]]
Specify EDNS option with code point code
and optionally payload of value
as a
hexadecimal string. code
can be
either an EDNS option name (for example,
NSID
or ECS
),
or an arbitrary numeric value. +noednsopt
clears the EDNS options to be sent.
+[no]expire
Send an EDNS Expire option.
+[no]fail
Do not try the next server if you receive a SERVFAIL. The default is to not try the next server which is the reverse of normal stub resolver behavior.
+[no]header-only
Send a query with a DNS header without a question section. The default is to add a question section. The query type and query name are ignored when this is set.
+[no]identify
Show [or do not show] the IP address and port number
that supplied the answer when the
+short
option is enabled. If
short form answers are requested, the default is not
to show the source address and port number of the
server that provided the answer.
+[no]idnin
Process [do not process] IDN domain names on input. This requires IDN SUPPORT to have been enabled at compile time.
The default is to process IDN input when standard output is a tty. The IDN processing on input is disabled when dig output is redirected to files, pipes, and other non-tty file descriptors.
+[no]idnout
Convert [do not convert] puny code on output. This requires IDN SUPPORT to have been enabled at compile time.
The default is to process puny code on output when standard output is a tty. The puny code processing on output is disabled when dig output is redirected to files, pipes, and other non-tty file descriptors.
+[no]ignore
Ignore truncation in UDP responses instead of retrying with TCP. By default, TCP retries are performed.
+[no]keepalive
Send [or do not send] an EDNS Keepalive option.
+[no]keepopen
Keep the TCP socket open between queries and reuse
it rather than creating a new TCP socket for each
lookup. The default is +nokeepopen
.
+[no]mapped
Allow mapped IPv4 over IPv6 addresses to be used. The
default is +mapped
.
+[no]multiline
Print records like the SOA records in a verbose multi-line format with human-readable comments. The default is to print each record on a single line, to facilitate machine parsing of the dig output.
+ndots=D
Set the number of dots that have to appear in
name
to D
for it to be considered absolute. The default value
is that defined using the ndots statement in
/etc/resolv.conf
, or 1 if no
ndots statement is present. Names with fewer dots
are interpreted as relative names and will be searched
for in the domains listed in the search
or domain
directive in
/etc/resolv.conf
if
+search
is set.
+[no]nsid
Include an EDNS name server ID request when sending a query.
+[no]nssearch
When this option is set, dig attempts to find the authoritative name servers for the zone containing the name being looked up and display the SOA record that each name server has for the zone.
+[no]onesoa
Print only one (starting) SOA record when performing an AXFR. The default is to print both the starting and ending SOA records.
+[no]opcode=value
Set [restore] the DNS message opcode to the specified value. The default value is QUERY (0).
+padding=value
Pad the size of the query packet using the EDNS Padding option
to blocks of value
bytes. For example,
+padding=32
would cause a 48-byte query to
be padded to 64 bytes. The default block size is 0, which
disables padding. The maximum is 512. Values are
ordinarily expected to be powers of two, such as 128;
however, this is not mandatory. Responses to
padded queries may also be padded, but only if the query
uses TCP or DNS COOKIE.
+[no]qr
Print [do not print] the query as it is sent. By default, the query is not printed.
+[no]question
Print [do not print] the question section of a query when an answer is returned. The default is to print the question section as a comment.
+[no]rdflag
A synonym for +[no]recurse
.
+[no]recurse
Toggle the setting of the RD (recursion desired) bit
in the query. This bit is set by default, which means
dig normally sends recursive
queries. Recursion is automatically disabled when
the +nssearch
or
+trace
query options are used.
+retry=T
Sets the number of times to retry UDP queries to
server to T
instead of the
default, 2. Unlike +tries
,
this does not include the initial query.
+[no]rrcomments
Toggle the display of per-record comments in the output (for example, human-readable key information about DNSKEY records). The default is not to print record comments unless multiline mode is active.
+[no]search
Use [do not use] the search list defined by the
searchlist or domain directive in
resolv.conf
(if any). The search
list is not used by default.
'ndots' from resolv.conf
(default 1)
which may be overridden by +ndots
determines if the name will be treated as relative
or not and hence whether a search is eventually
performed or not.
+[no]short
Provide a terse answer. The default is to print the answer in a verbose form.
+[no]showsearch
Perform [do not perform] a search showing intermediate results.
+[no]sigchase
This feature is now obsolete and has been removed; use delv instead.
+split=W
Split long hex- or base64-formatted fields in resource
records into chunks of W
characters (where W
is rounded
up to the nearest multiple of 4).
+nosplit
or
+split=0
causes fields not to
be split at all. The default is 56 characters, or
44 characters when multiline mode is active.
+[no]stats
This query option toggles the printing of statistics: when the query was made, the size of the reply and so on. The default behavior is to print the query statistics.
+[no]subnet=addr[/prefix-length]
Send (don't send) an EDNS Client Subnet option with the specified IP address or network prefix.
dig +subnet=0.0.0.0/0, or simply dig +subnet=0 for short, sends an EDNS CLIENT-SUBNET option with an empty address and a source prefix-length of zero, which signals a resolver that the client's address information must not be used when resolving this query.
+[no]tcp
Use [do not use] TCP when querying name servers. The
default behavior is to use UDP unless a type
any
or ixfr=N
query is requested, in which case the default is TCP.
AXFR queries always use TCP.
+timeout=T
Sets the timeout for a query to
T
seconds. The default
timeout is 5 seconds.
An attempt to set T
to less
than 1 will result
in a query timeout of 1 second being applied.
+[no]topdown
This feature is related to dig +sigchase, which is obsolete and has been removed. Use delv instead.
+[no]trace
Toggle tracing of the delegation path from the root name servers for the name being looked up. Tracing is disabled by default. When tracing is enabled, dig makes iterative queries to resolve the name being looked up. It will follow referrals from the root servers, showing the answer from each server that was used to resolve the lookup.
If @server is also specified, it affects only the initial query for the root zone name servers.
+dnssec is also set when +trace is set to better emulate the default queries from a nameserver.
+tries=T
Sets the number of times to try UDP queries to server
to T
instead of the default,
3. If T
is less than or equal
to zero, the number of tries is silently rounded up
to 1.
+trusted-key=####
Formerly specified trusted keys for use with dig +sigchase. This feature is now obsolete and has been removed; use delv instead.
+[no]ttlid
Display [do not display] the TTL when printing the record.
+[no]ttlunits
Display [do not display] the TTL in friendly human-readable time units of "s", "m", "h", "d", and "w", representing seconds, minutes, hours, days and weeks. Implies +ttlid.
+[no]unknownformat
Print all RDATA in unknown RR type presentation format (RFC 3597). The default is to print RDATA for known types in the type's presentation format.
+[no]vc
Use [do not use] TCP when querying name servers. This
alternate syntax to +[no]tcp
is provided for backwards compatibility. The "vc"
stands for "virtual circuit".
+[no]zflag
Set [do not set] the last unassigned DNS header flag in a DNS query. This flag is off by default.
The BIND 9 implementation of dig
supports
specifying multiple queries on the command line (in addition to
supporting the -f
batch file option). Each of those
queries can be supplied with its own set of flags, options and query
options.
In this case, each query
argument
represent an
individual query in the command-line syntax described above. Each
consists of any of the standard options and flags, the name to be
looked up, an optional query type and class and any query options that
should be applied to that query.
A global set of query options, which should be applied to all queries,
can also be supplied. These global query options must precede the
first tuple of name, class, type, options, flags, and query options
supplied on the command line. Any global query options (except
+[no]cmd
and +[no]short
options)
can be overridden by a query-specific set of query options.
For example:
dig +qr www.isc.org any -x 127.0.0.1 isc.org ns +noqr
shows how dig could be used from the
command line
to make three lookups: an ANY query for www.isc.org
, a
reverse lookup of 127.0.0.1 and a query for the NS records of
isc.org
.
A global query option of +qr
is
applied, so
that dig shows the initial query it made
for each
lookup. The final query has a local query option of
+noqr
which means that dig
will not print the initial query when it looks up the NS records for
isc.org
.
If dig has been built with IDN (internationalized
domain name) support, it can accept and display non-ASCII domain names.
dig appropriately converts character encoding of
domain name before sending a request to DNS server or displaying a
reply from the server.
If you'd like to turn off the IDN support for some reason, use
parameters +noidnin
and
+noidnout
.
BIND 9.12.4-P2