dig(1) BIND 9 dig(1)

NAME

 dig - DNS lookup utility

SYNOPSIS

 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...]

DESCRIPTION

 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. 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 tries each of
 the servers listed in /etc/resolv.conf. If no usable server addresses
 are found, dig sends the query to the local host.
 When no command-line arguments or options are given, dig performs 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 behavior.
 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 to specify the domain name, or use "IN." and "CH." when
 looking up these top-level domains.

SIMPLE USAGE

 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
 are tried. If no usable addresses are found, dig sends 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 performs a lookup for an A record.

OPTIONS

 -4 This option indicates that only IPv4 should be used.
 -6 This option indicates that only IPv6 should be used.
 -b address[#port]
 This option sets 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.
 -c class
 This option sets the query class. The default class is IN; other
 classes are HS for Hesiod records or CH for Chaosnet records.
 -f file
 This option sets batch mode, in which 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 it would be presented as a
 query to dig using the command-line interface.
 -h Print a usage summary.
 -k keyfile
 This option tells dig to sign queries using TSIG or SIG(0) using
 a key read from the given file. Key files can be generated using
 tsig-keygen. 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 for TSIG and by looking
 up the KEY record in zone data for SIG(0).
 -m This option enables memory usage debugging.
 -p port
 This option sends the query to a non-standard port on the
 server, instead of the default port 53. This option is used to
 test a name server that has been configured to listen for
 queries on a non-standard port number.
 -q name
 This option specifies the domain name to query. This is useful
 to distinguish the name from other arguments.
 -r This option indicates that options from ${HOME}/.digrc should
 not be read. This is useful for scripts that need predictable
 behavior.
 -t type
 This option indicates the resource record type to query, which
 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 contains all 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 is displayed as described in RFC
 3597.
 -u This option indicates that print query times should be provided
 in microseconds instead of milliseconds.
 -v This option prints the version number and exits.
 -x addr
 This option sets 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 option 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.
 -y [hmac:]keyname:secret
 This option signs 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; if MD5 was disabled, the
 default is hmac-sha256.
 NOTE:
 Only the -k option should be used, rather than 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 ps1
 or in a history file maintained by the user's shell.

QUERY OPTIONS

 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:
 +aaflag, +noaaflag
 This option is a synonym for +aaonly, +noaaonly.
 +aaonly, +noaaonly
 This option sets the aa flag in the query.
 +additional, +noadditional
 This option displays [or does not display] the additional
 section of a reply. The default is to display it.
 +adflag, +noadflag
 This option sets [or does 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 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 indicates that some part of the
 answer was insecure or not validated. This bit is set by
 default.
 +all, +noall
 This option sets or clears all display flags.
 +answer, +noanswer
 This option displays [or does not display] the answer section of
 a reply. The default is to display it.
 +authority, +noauthority
 This option displays [or does not display] the authority section
 of a reply. The default is to display it.
 +badcookie, +nobadcookie
 This option retries the lookup with a new server cookie if a
 BADCOOKIE response is received.
 +besteffort, +nobesteffort
 This option attempts to display the contents of messages which
 are malformed. The default is to not display malformed answers.
 +bufsize[=B]
 This option sets the UDP message buffer size advertised using
 EDNS0 to B bytes. The maximum and minimum sizes of this buffer
 are 65535 and 0, respectively. +bufsize restores the default
 buffer size.
 +cd, +cdflag, +nocdflag
 This option sets [or does not set] the CD (checking disabled)
 bit in the query. This requests the server to not perform DNSSEC
 validation of responses.
 +class, +noclass
 This option displays [or does not display] the CLASS when
 printing the record.
 +cmd, +nocmd
 This option toggles the printing of the initial comment in the
 output, identifying the version of dig and the query options
 that have been applied. This option always has a global effect;
 it cannot be set globally and then overridden on a per-lookup
 basis. The default is to print this comment.
 +comments, +nocomments
 This option toggles the display of some comment lines in the
 output, with information about the packet header and OPT
 pseudosection, and the names of the response section. The
 default is to print these comments.
 Other types of comments in the output are not affected by this
 option, but can be controlled using other command-line switches.
 These include +cmd, +question, +stats, and +rrcomments.
 +cookie=####, +nocookie
 This option sends [or does not send] a COOKIE EDNS option, with
 an optional value. Replaying a COOKIE from a previous response
 allows 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.
 +crypto, +nocrypto
 This option toggles the display of cryptographic fields in
 DNSSEC records. The contents of these fields are unnecessary for
 debugging 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 ].
 +defname, +nodefname
 This option, which is deprecated, is treated as a synonym for
 +search, +nosearch.
 +dns64prefix, +nodns64prefix
 Lookup IPV4ONLY.ARPA AAAA and print any DNS64 prefixes found.
 +dnssec, +do, +nodnssec, +nodo
 This option requests that DNSSEC records be sent by setting the
 DNSSEC OK (DO) bit in the OPT record in the additional section
 of the query.
 +domain=somename
 This option sets the search list to contain the single domain
 somename, as if specified in a domain directive in
 /etc/resolv.conf, and enables search list processing as if the
 +search option were given.
 +edns[=#], +noedns
 This option specifies the EDNS version to query with. Valid
 values are 0 to 255. Setting the EDNS version causes an EDNS
 query to be sent. +noedns clears the remembered EDNS version.
 EDNS is set to 0 by default.
 +ednsflags[=#], +noednsflags
 This option sets 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) is silently ignored.
 By default, no Z bits are set.
 +ednsnegotiation, +noednsnegotiation
 This option enables/disables EDNS version negotiation. By
 default, EDNS version negotiation is enabled.
 +ednsopt[=code[:value]], +noednsopt
 This option specifies the EDNS option with code point code and
 an optional 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.
 +expire, +noexpire
 This option sends an EDNS Expire option.
 +fail, +nofail
 This option indicates that named should try [or not try] the
 next server if a SERVFAIL is received. The default is to not try
 the next server, which is the reverse of normal stub resolver
 behavior.
 +fuzztime[=value], +nofuzztime
 This option allows the signing time to be specified when
 generating signed messages. If a value is specified it is the
 seconds since 00:00:00 January 1, 1970 UTC ignoring leap
 seconds. If no value is specified 1646972129 (Fri 11 Mar 2022
 04:15:29 UTC) is used. The default is +nofuzztime and the
 current time is used.
 +header-only, +noheader-only
 This option sends 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.
 +https[=value], +nohttps
 This option indicates whether to use DNS over HTTPS (DoH) when
 querying name servers. When this option is in use, the port
 number defaults to 443. The HTTP POST request mode is used when
 sending the query.
 If value is specified, it will be used as the HTTP endpoint in
 the query URI; the default is /dns-query. So, for example, dig
 @example.com +https will use the URI
 https://example.com/dns-query.
 +https-get[=value], +nohttps-get
 Similar to +https, except that the HTTP GET request mode is used
 when sending the query.
 +https-post[=value], +nohttps-post
 Same as +https.
 +http-plain[=value], +nohttp-plain
 Similar to +https, except that HTTP queries will be sent over a
 non-encrypted channel. When this option is in use, the port
 number defaults to 80 and the HTTP request mode is POST.
 +http-plain-get[=value], +nohttp-plain-get
 Similar to +http-plain, except that the HTTP request mode is
 GET.
 +http-plain-post[=value], +nohttp-plain-post
 Same as +http-plain.
 +identify, +noidentify
 This option shows [or does 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.
 +idn, +noidn
 Enable or disable IDN processing. By default IDN is enabled for
 input query names, and for display when the output is a
 terminal.
 You can also turn off dig's IDN processing by setting the
 IDN_DISABLE environment variable.
 +ignore, +noignore
 This option ignores [or does not ignore] truncation in UDP
 responses instead of retrying with TCP. By default, TCP retries
 are performed.
 +keepalive, +nokeepalive
 This option sends [or does not send] an EDNS Keepalive option.
 +keepopen, +nokeepopen
 This option keeps [or does not keep] the TCP socket open between
 queries, and reuses it rather than creating a new TCP socket for
 each lookup. The default is +nokeepopen.
 +multiline, +nomultiline
 This option prints [or does not 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
 This option sets the number of dots (D) that must appear in name
 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 are searched for in the
 domains listed in the search or domain directive in
 /etc/resolv.conf if +search is set.
 +nsid, +nonsid
 When enabled, this option includes an EDNS name server ID
 request when sending a query.
 +nssearch, +nonssearch
 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. Addresses of servers that did not respond are also
 printed.
 +onesoa, +noonesoa
 When enabled, this option prints only one (starting) SOA record
 when performing an AXFR. The default is to print both the
 starting and ending SOA records.
 +opcode=value, +noopcode
 When enabled, this option sets (restores) the DNS message opcode
 to the specified value. The default value is QUERY (0).
 +padding=value
 This option pads the size of the query packet using the EDNS
 Padding option to blocks of value bytes. For example,
 +padding=32 causes 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.
 +proxy[=src_addr[#src_port]-dst_addr[#dst_port]], +noproxy
 When this option is set, dig adds PROXYv2 headers to the
 queries. When source and destination addresses are specified,
 the headers contain them and use the PROXY command. It means for
 the remote peer that the queries were sent on behalf of another
 node and that the PROXYv2 header reflects the original
 connection endpoints. The default source port is 0 and
 destination port is 53.
 For encrypted DNS transports, to prevent accidental information
 leakage, encryption is applied to the PROXYv2 headers: the
 headers are sent right after the handshake process has been
 completed.
 For plain DNS transports, no encryption is applied to the
 PROXYv2 headers.
 If the addressees are omitted, PROXYv2 headers, that use the
 LOCAL command set, are added instead. For the remote peer, that
 means that the queries were sent on purpose without being
 relayed, so the real connection endpoint addresses must be used.
 +proxy-plain[=src_addr[#src_port]-dst_addr[#dst_port], +noproxy-plain
 The same as +[no]proxy, but instructs dig to send PROXYv2
 headers ahead of any encryption, before any handshake messages
 are sent. That makes dig behave exactly how it is described in
 the PROXY protocol specification, but not all software expects
 such behaviour.
 Please consult the software documentation to find out if you
 need this option. (for example, dnsdist expects encrypted
 PROXYv2 headers sent over TLS when encryption is used, while
 HAProxy and many other software packages expect plain ones).
 For plain DNS transports the option is effectively an alias for
 the +[no]proxy described above.
 +qid=value
 This option specifies the query ID to use when sending queries.
 +qr, +noqr
 This option toggles the display of the query message as it is
 sent. By default, the query is not printed.
 +question, +noquestion
 This option toggles the display of the question section of a
 query when an answer is returned. The default is to print the
 question section as a comment.
 +raflag, +noraflag
 This option sets [or does not set] the RA (Recursion Available)
 bit in the query. The default is +noraflag. This bit is ignored
 by the server for QUERY.
 +rdflag, +nordflag
 This option is a synonym for +recurse, +norecurse.
 +recurse, +norecurse
 This option toggles 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 option is used.
 +retry=T
 This option sets the number of times to retry UDP and TCP
 queries to server to T instead of the default, 2. Unlike
 +tries, this does not include the initial query.
 +rrcomments, +norrcomments
 This option toggles 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.
 +search, +nosearch
 This option uses [or does 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 whether the name is treated as relative and
 hence whether a search is eventually performed.
 +short, +noshort
 This option toggles whether a terse answer is provided. The
 default is to print the answer in a verbose form. This option
 always has a global effect; it cannot be set globally and then
 overridden on a per-lookup basis.
 +showbadcookie, +noshowbadcookie
 This option toggles whether to show the message containing the
 BADCOOKIE rcode before retrying the request or not. The default
 is to not show the messages.
 +showsearch, +noshowsearch
 This option performs [or does not perform] a search showing
 intermediate results.
 +split=W
 This option splits 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.
 +stats, +nostats
 This option toggles the printing of statistics: when the query
 was made, the size of the reply, etc. The default behavior is to
 print the query statistics as a comment after each lookup.
 +subnet=addr[/prefix-length], +nosubnet
 This option sends [or does not 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.
 +tcflag, +notcflag
 This option sets [or does not set] the TC (TrunCation) bit in
 the query. The default is +notcflag. This bit is ignored by the
 server for QUERY.
 +tcp, +notcp
 This option indicates whether to 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. To prevent retry over TCP when TC=1
 is returned from a UDP query, use +ignore.
 +timeout=T
 This option sets the timeout for a query to T seconds. The
 default timeout is 5 seconds. An attempt to set T to less than 1
 is silently set to 1.
 +tls, +notls
 This option indicates whether to use DNS over TLS (DoT) when
 querying name servers. When this option is in use, the port
 number defaults to 853.
 +tls-ca[=file-name], +notls-ca
 This option enables remote server TLS certificate validation for
 DNS transports, relying on TLS. Certificate authorities
 certificates are loaded from the specified PEM file (file-name).
 If the file is not specified, the default certificates from the
 global certificates store are used.
 +tls-certfile=file-name, +tls-keyfile=file-name, +notls-certfile,
 +notls-keyfile
 These options set the state of certificate-based client
 authentication for DNS transports, relying on TLS. Both
 certificate chain file and private key file are expected to be
 in PEM format. Both options must be specified at the same time.
 +tls-hostname=hostname, +notls-hostname
 This option makes dig use the provided hostname during remote
 server TLS certificate verification. Otherwise, the DNS server
 name is used. This option has no effect if +tls-ca is not
 specified.
 +trace, +notrace
 This option toggles 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 follows
 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 set when +trace is set, to better emulate the default
 queries from a name server.
 Note that the delv +ns option can also be used for tracing the
 resolution of a name from the root (see delv).
 +tries=T
 This option sets the number of times to try UDP and TCP 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.
 +ttlid, +nottlid
 This option displays [or does not display] the TTL when printing
 the record.
 +ttlunits, +nottlunits
 This option displays [or does not display] the TTL in friendly
 human-readable time units of s, m, h, d, and w, representing
 seconds, minutes, hours, days, and weeks. This implies +ttlid.
 +unknownformat, +nounknownformat
 This option prints 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.
 +vc, +novc
 This option uses [or does not use] TCP when querying name
 servers. This alternate syntax to +tcp is provided for backwards
 compatibility. The vc stands for "virtual circuit."
 +yaml, +noyaml
 When enabled, this option prints the responses (and, if +qr is
 in use, also the outgoing queries) in a detailed YAML format.
 +zflag, +nozflag
 This option sets [or does not set] the last unassigned DNS
 header flag in a DNS query. This flag is off by default.

MULTIPLE QUERIES

 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 represents 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 +cmd and +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 can 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
 does not print the initial query when it looks up the NS records for
 isc.org.

RETURN CODES

 dig return codes are:
 0 DNS response received, including NXDOMAIN status
 1 Usage error
 8 Couldn't open batch file
 9 No reply from server
 10 Internal error

FILES

 /etc/resolv.conf
 ${HOME}/.digrc

SEE ALSO

 delv(1) , host(1) , named(8) , dnssec-keygen(8) , RFC 1035.

BUGS

 There are probably too many query options.

AUTHOR

 Internet Systems Consortium

COPYRIGHT

 2024, Internet Systems Consortium
9.20.3 2024年10月07日 dig(1)