dig (DNS lookup utility)

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.

Syntax:
       dig [@global-server] [domain] [q-type] [q-class] {q-opt} {global-d-opt}
           host [@local-server] {local-d-opt}
              [ host [@local-server] {local-d-opt} [...]]

Where:
  domain	  is in the Domain Name System

  q-class  is one of (in, hs, ch, ...) [default: in]

  q-type   is one of (a, any, mx, ns, soa, hinfo, axfr, txt,...) [default:a]
                 (Use ixfr=version for type ixfr)

  q-opt    is one of:

   -4    Force dig to only use IPv4 query transport.

   -6    Force dig to only use IPv6 query transport.

   -b address [#port]
         Bind to the source IP address/port.
         This must be a valid address on one of the host's network interfaces or "0.0.0.0" or "::".
         An optional port can be specified by appending "#port"

   -c class
         Over-ride the default query class (IN for internet).
         class is any valid class, such as HS for Hesiod records or CH for CHAOSNET records.

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

   -i    Use IP6.INT for IPv6 reverse lookups.

-k keyfile Specify tsig key file. Sign the DNS queries sent by dig and their responses using transaction signatures (TSIG key file). You can also specify the TSIG key itself on the command line using the -y option; 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. -m Enable memory usage debugging. -p port# Specify a non-standard port number to be queried, default = 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. -q name Specify query name -t type Set the query type to type, any valid query type which is supported in BIND9. The default query type "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. -u Display times in usec instead of msec. -x addr Reverse lookups - mapping addresses to names: 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 11.12.13.10.in-addr.arpa 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. d-opt is of the form +keyword[=value], where keyword is: +[no]aaonly Sets the "aa" flag in the query. +[no]aaflag A synonym for +[no]aaonly. +[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. +[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]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]cl 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]crypto Control display of cryptographic fields in records. +[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. +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. +ednsflags=### Set EDNS flag bits. +[no]ednsnegotiation Set EDNS version negotiation. +noednsopt Clear list of +ednsopt options. +[no]expire Request time to expire. +[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]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]idnout Convert IDN response. +[no]ignore Ignore truncation in UDP responses instead of retrying with TCP. By default, TCP retries are performed. +[no]keepopen Keep the TCP socket open between queries. +[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. +[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 AXFR prints only one soa record. +[no]opcode=### Set the opcode of the request. +[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]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 Control display of per-record comments. +[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. +[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]split=## Split hex/base64 fields into chunks. +[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. +subnet=addr Set edns-client-subnet option. +[no]tcp 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. +time=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]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. +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. +[no]ttlid Display [do not display] the TTL when printing the record. +[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". global d-opts and servers (before host name) affect all queries. local d-opts and servers (after host name) affect only that lookup. -h Print a brief summary of the command-line arguments and options. -v Print version and exit.

Although dig is normally used with command-line arguments, it also has a batch mode of operation for reading lookup requests from a file. Unlike earlier versions, the BIND9 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

When no command line arguments or options are given, 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.

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

Commonly used record types

A (Host address)
AAAA (IPv6 host address)
ALIAS (Auto resolved alias)
CNAME (Canonical name for an alias)
MX (Mail eXchange)
NS (Name Server)
PTR (Pointer)
SOA (Start Of Authority)
SRV (location of service)
TXT (Descriptive text)

Examples

List the DNS A records for ss64.com:
$ dig ss64.com

or
$ dig ss64.com A

List the DNS AAAA (ipv6) records for ss64.com:
$ dig ss64.com AAAA

List the DNS A records for ss64.com using Google DNS (8.8.8.8) instead of your local cache:
$ dig ss64.com @8.8.8.8

List the Signature record (SIG record) for ss64.com:
$ dig ss64.com SIG

List the Mail exchanger record (MX record) for ss64.com:
$ dig ss64.com MX

Test your DNS resolver's source port behavior:
$ dig +short porttest.dns-oarc.net TXT

“Businessmen they drink my wine, Plowmen dig my earth, But none of them along the line, Know what any of it is worth” - Bob Dylan

Related macOS commands

dscacheutil - Query or flush the Directory Service/DNS cache.
Dig web interface - Online Dig.
ViewDNS.info - Online IP and DNS lookups.


 
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