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 (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
      /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 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.
	    
nameis 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.
	    
      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 "0.0.0.0" or "::".  An optional
      port
      may be specified by appending "#<port>"
    
      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 interface.
    
      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 is useful to distinguish the
      name from other arguments.
    
      The -v causes dig to
      print the version number and exit.
    
      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
      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.
    
      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.
    
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:
      
+[no]aaflag
	      A synonym for +[no]aaonly.
	    
+[no]aaonlySets the "aa" flag in the query.
+[no]additionalDisplay [do not display] the additional section of a reply. The default is to display it.
+[no]adflagSet [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]allSet or clear all display flags.
+[no]answerDisplay [do not display] the answer section of a reply. The default is to display it.
+[no]authorityDisplay [do not display] the authority section of a reply. The default is to display it.
+[no]besteffortAttempt 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]cdflagSet [do not set] the CD (checking disabled) bit in the query. This requests the server to not perform DNSSEC validation of responses.
+[no]clDisplay [do not display] the CLASS when printing the record.
+[no]cmdToggles 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]commentsToggle the display of comment lines in the output. The default is to print comments.
+[no]cryptoToggle 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]dnssecRequests 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.
	    
+[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]expireSend an EDNS Expire option.
+[no]failDo 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]ignoreIgnore truncation in UDP responses instead of retrying with TCP. By default, TCP retries are performed.
+[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]multilinePrint 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]nsidInclude an EDNS name server ID request when sending a query.
+[no]nssearchWhen 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]onesoaPrint only one (starting) SOA record when performing an AXFR. The default is to print both the starting and ending SOA records.
+[no]qrPrint [do not print] the query as it is sent. By default, the query is not printed.
+[no]questionPrint [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]rrcommentsToggle 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.
	    
+[no]shortProvide a terse answer. The default is to print the answer in a verbose form.
+[no]showsearchPerform [do not perform] a search showing intermediate results.
+[no]sigchaseChase DNSSEC signature chains. Requires dig be compiled with -DDIG_SIGCHASE.
+[no]sit[=####]
	      Send a Source Identity Token EDNS option, with optional
	      value.  Replaying a SIT from a previous response will
	      allow the server to identify a previous client.  The
	      default is +nosit.  Currently using
	      experimental value 65001 for the option code.
	    
+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]statsThis 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/prefixSend an EDNS Client Subnet option with the speciifed IP address or network prefix.
+[no]tcp
	      Use [do not use] TCP when querying name servers. The
	      default behavior is to use UDP unless an
	      ixfr=N query is requested, in which
	      case the default is TCP.  AXFR queries always use
	      TCP.
	    
+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]topdownWhen chasing DNSSEC signature chains perform a top-down validation. Requires dig be compiled with -DDIG_SIGCHASE.
+[no]traceToggle 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.
+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=####
	      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
	      directory.
	    
Requires dig be compiled with -DDIG_SIGCHASE.
+[no]ttlidDisplay [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".
	    
      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 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, defines
      the IDN_DISABLE environment variable.
      The IDN support is disabled if the variable is set when 
      dig runs.