Command Line Tools: DIG

Apple messed-up yet again, removing easy-to-use tools from the reach of the masses. However, the functionality remains available using the DIG command-line tool. Below is the documentation for using DIG on your Mac…



dig – DNS lookup utility

dig [@server] [-b address] [-c class] [-f filename] [-k filename] [-m] [-p port#] [-q name] [-t type]
[-x addr] [-y [hmac:]name:key] [-4] [-6] [name] [type] [class] [queryopt…]

dig [-h]

dig [global-queryopt…] [query…]

dig (domain information groper) 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

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 IN and CH class names overlap with the IN and CH top level domains 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


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 and queries the name servers listed there.
The reply from the name server that responds is displayed.

is the name of the resource record that is to be looked up.

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.

The -b option sets the source IP address of the query to address. This must be a valid address on one
of the host’s network interfaces or "" or "::". An optional port may be specified by appending

The default query class (IN for internet) is overridden by the -c option. class is any valid class,
such as HS for Hesiod records or CH for Chaosnet records.

The -f option makes dig operate in batch mode by reading a list of lookup requests to process from
the file filename. The file contains a number of queries, one per line. Each entry in the file should
be organized in the same way they would be presented as queries to dig using the command-line

The -m option enables memory usage debugging.

If a non-standard port number is to be queried, the -p option is used. port# is the port number that
dig will send its queries instead of the standard DNS port number 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.

The -4 option forces dig to only use IPv4 query transport. The -6 option forces dig to only use IPv6
query transport.

The -t option sets the query type to type. It can be any valid query type which is supported in BIND
9. 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, type is set 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.

The -q option sets the query name to name. This useful do distinguish the name from other arguments.

Reverse lookups — mapping addresses to names — are simplified by the -x option. addr is an IPv4
address in dotted-decimal notation, or a colon-delimited IPv6 address. When this option is used,
there is no need to provide the name, class and type arguments. dig automatically performs a lookup
for a name like and sets the query type and class to PTR and IN
respectively. By default, IPv6 addresses are looked up using nibble format under the IP6.ARPA domain.
To use the older RFC1886 method using the IP6.INT domain specify the -i option. Bit string labels
(RFC2874) are now experimental and are not attempted.

To sign the DNS queries sent by dig and their responses using transaction signatures (TSIG), specify
a TSIG key file using the -k option. You can also specify the TSIG key itself on the command line
using the -y option; hmac is the type of the TSIG, default HMAC-MD5, name is the name of the TSIG key
and key is the actual key. The key is a base-64 encoded string, typically generated by
dnssec-keygen(8). Caution should be taken when using the -y option on multi-user systems as the key
can be visible in the output from ps(1) or in the shell’s history file. 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.

The dig command does not use the host name and address resolution or the DNS query routing mechanisms
used by other processes running on Mac OS X. The results of name or address queries printed by dig
may differ from those found by other processes that use the Mac OS X native name and address
resolution mechanisms. The results of DNS queries may also differ from queries that use the Mac OS X
DNS routing library.

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. The
query options are:

Use [do not use] TCP when querying name servers. The default behavior is to use UDP unless an
AXFR or IXFR query is requested, in which case a TCP connection is used.

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".

Ignore truncation in UDP responses instead of retrying with TCP. By default, TCP retries are

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.

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.

Perform [do not perform] a search showing intermediate results.

Deprecated, treated as a synonym for +[no]search

Sets the "aa" flag in the query.

A synonym for +[no]aaonly.

Set [do not set] the AD (authentic data) bit in the query. The AD bit currently has a standard
meaning only in responses, not in queries, but the ability to set the bit in the query is
provided for completeness.

Set [do not set] the CD (checking disabled) bit in the query. This requests the server to not
perform DNSSEC validation of responses.

Display [do not display] the CLASS when printing the record.

Display [do not display] the TTL when printing the record.

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.

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

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.

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.

Provide a terse answer. The default is to print the answer in a verbose form.

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.

Toggle the display of comment lines in the output. The default is to print comments.

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.

Print [do not print] the query as it is sent. By default, the query is not printed.

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.

Display [do not display] the answer section of a reply. The default is to display it.

Display [do not display] the authority section of a reply. The default is to display it.

Display [do not display] the additional section of a reply. The default is to display it.

Set or clear all display flags.

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.

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.

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.

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.

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.

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.

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

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.

Attempt to display the contents of messages which are malformed. The default is to not display
malformed answers.

Requests DNSSEC records be sent by setting the DNSSEC OK bit (DO) in the OPT record in the
additional section of the query.

Chase DNSSEC signature chains. Requires dig be compiled with -DDIG_SIGCHASE.

Specifies a file containing trusted keys to be used with +sigchase. Each DNSKEY record must be on
its own line.

If not specified dig will look for /etc/trusted-key.key then trusted-key.key in the current

Requires dig be compiled with -DDIG_SIGCHASE.

When chasing DNSSEC signature chains perform a top-down validation. Requires dig be compiled with

Include an EDNS name server ID request when sending a query.

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 the +[no]cmd option) can be
overridden by a query-specific set of query options. For example:

dig +qr any -x ns +noqr

shows how dig could be used from the command line to make three lookups: an ANY query for, a reverse lookup of and a query for the NS records of 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

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, defines the IDN_DISABLE environment variable. The IDN support is disabled if
the variable is set when dig runs.