xref: /openbsd-src/usr.bin/dig/dig.1 (revision a0747c9f67a4ae71ccb71e62a28d1ea19e06a63c)
1.\" $OpenBSD: dig.1,v 1.5 2021/03/12 05:18:01 jsg Exp $
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17.Dd $Mdocdate: March 12 2021 $
18.Dt DIG 1
19.Os
20.Sh NAME
21.Nm dig
22.Nd DNS lookup utility
23.Sh SYNOPSIS
24.Nm
25.Op Pf @ Ar server
26.Op Fl 46hiuv
27.Op Fl b Ar sourceaddr Ns Op Pf # Ar port
28.Op Fl c Ar class
29.Op Fl f Ar file
30.Op Fl k Ar keyfile
31.Op Fl p Ar port
32.Op Fl q Ar name
33.Op Fl t Ar type
34.Op Fl x Ar addr
35.Op Fl y Oo Ar hmac : Oc Ns Ar name : Ns Ar key
36.Op Ar name
37.Op Ar type
38.Op Ar class
39.Op Pf + Ar queryopt ...
40.Sh DESCRIPTION
41The
42.Nm
43command is a flexible tool for interrogating DNS name servers.
44It performs DNS lookups and displays the answers that are returned from the name
45servers that were queried.
46Although
47.Nm
48is normally used with command line arguments, it also has a batch mode of
49operation for reading lookup requests from a file.
50When no command line arguments or options are given,
51.Nm
52will perform an NS query for '.' (the root).
53.Pp
54A typical invocation of
55.Nm
56looks like:
57.Pp
58.Dl dig @server [options] name type [class] [+queryopt]
59.Bl -tag -width +queryopt
60.It Pf @ Ar server
61The name or IP address of the name server to query.
62When the argument is a hostname,
63.Nm
64resolves that name before querying that name server.
65If no
66.Ar server
67argument is provided,
68.Nm
69will try each of the servers listed in
70.Xr resolv.conf 5 .
71If no usable addresses are found,
72.Nm
73will send the query to the local host.
74The reply from the name server that responds is displayed.
75.It Ar name
76The name of the resource record that is to be looked up.
77.It Ar type
78The type of query, as documented for
79.Fl t .
80The default is
81.Cm A .
82.It Ar class
83The query class, as documented for
84.Fl c .
85The default is
86.Cm IN .
87.It Pf + Ar queryopt
88One or more query options,
89as documented in
90.Sx QUERY OPTIONS ,
91below.
92.El
93.Pp
94The options are as follows:
95.Bl -tag -width Ds
96.It Fl 4
97Use IPv4 only.
98.It Fl 6
99Use IPv6 only.
100.It Fl b Ar sourceaddr Ns Op Pf # Ar port
101Set the source IP address of the query, which is useful on machines
102with multiple interfaces.
103The
104.Ar sourceaddr
105must be a valid address on one of the host's network interfaces, or
106"0.0.0.0" or "::". An optional port may be specified by appending
107"#<port>".
108.It Fl c Ar class
109Set the query class.
110The default is
111.Cm IN ;
112other classes are
113.Cm HS
114for Hesiod records and
115.Cm CH
116for Chaosnet records.
117.It Fl f Ar file
118Batch mode:
119.Nm
120reads a list of lookup requests to process from the given
121.Ar file .
122Each line in the file should be organized in the same way they would be
123presented as queries to
124.Nm
125using the command-line interface.
126.It Fl h
127Display a brief summary of command line arguments and options.
128.It Fl i
129Do reverse IPv6 lookups using the obsolete RFC 1886 IP6.INT domain, which is no
130longer in use.
131Obsolete bit string label queries (RFC 2874) are not attempted.
132.It Fl k Ar keyfile
133Sign queries using TSIG.
134The format of the
135.Ar keyfile
136is as follows:
137.Bd -literal -offset indent
138key "keyname" {
139	algorithm hmac;
140	secret "base64-secret";
141};
142.Ed
143.Pp
144.Ar keyname
145is the name of the key, and
146.Ar base64-secret
147is the base64-encoded shared secret.
148.Ar hmac
149is the name of the key algorithm;
150valid choices are
151.Cm hmac-sha1 ,
152.Cm hmac-sha224 ,
153.Cm hmac-sha256 ,
154.Cm hmac-sha384 ,
155and
156.Cm hmac-sha512 .
157.It Fl p Ar port
158Send the query to a non-standard port on the server, instead of the default port
15953.
160This option would be used to test a name server that has been configured to
161listen for queries on a non-standard port number.
162.It Fl q Ar name
163The domain name to query.
164This is useful to distinguish the
165.Ar name
166from other arguments.
167.It Fl t Ar type
168The resource record type to query.
169It can be any valid query type.
170If it is a resource record type supported in BIND 9, it can be given by the
171type mnemonic (such as
172.Cm NS
173or
174.Cm AAAA ) .
175The default query type is
176.Cm A ,
177unless the
178.Fl x
179option is supplied to indicate a reverse lookup.
180A zone transfer can be requested by specifying a type of
181.Cm AXFR .
182When an incremental zone transfer is required, set the
183.Ar type
184to
185.Cm IXFR Ns = Ns Ar N .
186The incremental zone transfer will contain the changes made to the zone since
187the serial number in the zone's SOA record was
188.Ar N .
189.Pp
190All resource record types can be expressed as
191.Cm TYPE Ns Ar nn ,
192where
193.Ar nn
194is the number of the type.
195If the resource record type is not supported in BIND 9, the result will be
196displayed as described in RFC 3597.
197.It Fl u
198Print query times in microseconds instead of milliseconds.
199.It Fl v
200Print the version number and exit.
201.It Fl x Ar addr
202Simplified reverse lookups, for mapping addresses to names.
203The
204.Ar addr
205is an IPv4 address in dotted-decimal notation, or a colon-delimited IPv6
206address.
207When the
208.Fl x
209is used, there is no need to provide the
210.Ar name ,
211.Ar class
212and
213.Ar type
214arguments.
215.Nm
216automatically performs a lookup for a name like
217.Ql 94.2.0.192.in-addr.arpa
218and sets the query type and class to
219.Cm PTR
220and
221.Cm IN
222respectively.
223IPv6 addresses are looked up using nibble format under the IP6.ARPA domain
224(but see also the
225.Fl i
226option).
227.It Fl y Xo
228.Op Ar hmac : Ns
229.Ar keyname : Ns
230.Ar secret
231.Xc
232Sign queries using TSIG with the given authentication key.
233.Ar keyname
234is the name of the key, and
235.Ar secret
236is the base64 encoded shared secret.
237.Ar hmac
238is the name of the key algorithm;
239valid choices are
240.Cm hmac-sha1 ,
241.Cm hmac-sha224 ,
242.Cm hmac-sha256 ,
243.Cm hmac-sha384 ,
244and
245.Cm hmac-sha512 .
246If
247.Ar hmac
248is not specified, the default is
249.Cm hmac-sha256 .
250.Pp
251NOTE: You should use the
252.Fl k
253option and
254avoid the
255.Fl y
256option, because
257with
258.Fl y
259the shared secret is supplied as a command line argument in clear text.
260This may be visible in the output from
261.Xr ps 1
262or in a history file maintained by the user's shell.
263.El
264.Pp
265The
266.Cm IN
267and
268.Cm CH
269class names overlap with the IN and CH top level domain names.
270Either use the
271.Fl t
272and
273.Fl c
274options to specify the type and class, use the
275.Fl q
276to specify the domain name, or use "IN." and "CH." when looking up these top
277level domains.
278.Sh QUERY OPTIONS
279.Nm
280provides a number of query options which affect the way in which lookups are
281made and the results displayed.
282Some of
283these set or reset flag bits in the query header, some determine which sections
284of the answer get printed, and others determine the timeout and retry
285strategies.
286.Pp
287Each query option is identified by a keyword preceded by a plus sign
288.Pq Cm + .
289Some keywords set or reset an option.
290These may be preceded by the string
291.Cm no
292to negate the meaning of that keyword.
293Other keywords assign values to options like the timeout interval.
294They have the form
295.Cm + Ns Ar keyword Ns = Ns Ar value .
296Keywords may be abbreviated, provided the abbreviation is unambiguous; for
297example,
298.Cm +cd
299is equivalent
300to
301.Cm +cdflag .
302The query options are:
303.Bl -tag -width Ds
304.It Xo
305.Cm + Ns
306.Op Cm no Ns
307.Cm aaflag
308.Xc
309A synonym for
310.Xo
311.Cm + Ns
312.Op Cm no Ns
313.Cm aaonly .
314.Xc
315.It Xo
316.Cm + Ns
317.Op Cm no Ns
318.Cm aaonly
319.Xc
320Set the "aa" flag in the query (off by default).
321.It Xo
322.Cm + Ns
323.Op Cm no Ns
324.Cm additional
325.Xc
326Display the additional section of a reply (on by default).
327.It Xo
328.Cm + Ns
329.Op Cm no Ns
330.Cm adflag
331.Xc
332Set the AD (authentic data) bit in the query (on by default).
333This requests the server to return whether all of the answer and authority
334sections have all been validated as secure according to the security policy of
335the server.
336AD=1 indicates that all records have been validated as secure and the answer is
337not from an OPT-OUT range.
338AD=0 indicates that some part of the answer was insecure or not validated.
339.It Xo
340.Cm + Ns
341.Op Cm no Ns
342.Cm all
343.Xc
344Set or clear all display flags.
345.It Xo
346.Cm + Ns
347.Op Cm no Ns
348.Cm answer
349.Xc
350Display the answer section of a reply (on by default).
351.It Xo
352.Cm + Ns
353.Op Cm no Ns
354.Cm authority
355.Xc
356Display the authority section of a reply (on by default).
357.It Xo
358.Cm + Ns
359.Op Cm no Ns
360.Cm besteffort
361.Xc
362Attempt to display the contents of messages which are malformed (on by
363default).
364.It Cm +bufsize Ns = Ns Ar #
365Set the UDP message buffer size advertised using EDNS0 to
366.Ar #
367bytes.
368The maximum and minimum sizes of this buffer are 65535 and 0 respectively.
369Values outside this range are rounded up or down appropriately.
370Values other than zero will cause an EDNS query to be sent.
371.It Xo
372.Cm + Ns
373.Op Cm no Ns
374.Cm cdflag
375.Xc
376Set the CD (checking disabled) bit in the query (off by default).
377This requests the server to not perform DNSSEC validation of responses.
378.It Xo
379.Cm + Ns
380.Op Cm no Ns
381.Cm class
382.Xc
383Display the CLASS when printing the record (on by default).
384.It Xo
385.Cm + Ns
386.Op Cm no Ns
387.Cm cmd
388.Xc
389Print an initial comment identifying the version of
390.Nm
391and the query options that have been applied (on by default).
392.It Xo
393.Cm + Ns
394.Op Cm no Ns
395.Cm comments
396.Xc
397Display comment lines in the output (on by default).
398.It Xo
399.Cm + Ns
400.Op Cm no Ns
401.Cm cookie Ns
402.Op = Ns Ar value
403.Xc
404Send a COOKIE EDNS option, containing an optional
405.Ar value
406(off by default).
407Replaying a COOKIE from a previous response will allow the server to
408identify a previous client.
409.Pp
410.Cm +cookie
411is automatically set when
412.Cm +trace
413is in use, to better emulate the default queries from a name server.
414.Pp
415This option was formerly called
416.Xo
417.Cm + Ns
418.Op Cm no Ns
419.Cm sit
420.Xc
421(Server Identity Token).
422In BIND 9.10.0 through BIND 9.10.2,
423it sent the experimental option code 65001.
424This was changed to option code 10 in BIND 9.10.3 when the DNS
425COOKIE option was allocated.
426.Pp
427The
428.Xo
429.Cm + Ns
430.Op Cm no Ns
431.Cm sit
432.Xc
433option is now deprecated, but has been retained as a synonym for
434.Xo
435.Cm + Ns
436.Op Cm no Ns
437.Cm cookie
438.Xc
439for backward compatibility within the BIND 9.10 branch.
440.It Xo
441.Cm + Ns
442.Op Cm no Ns
443.Cm crypto
444.Xc
445Display cryptographic fields in DNSSEC records (on by default).
446The contents of these field are unnecessary to debug most DNSSEC validation
447failures and removing them makes it easier to see the common failures.
448When omitted they are replaced by the string "[omitted]" or in the DNSKEY case
449the key id is displayed as the replacement, e.g. "[ key id = value ]".
450.It Xo
451.Cm + Ns
452.Op Cm no Ns
453.Cm defname
454.Xc
455Deprecated, treated as a synonym for
456.Xo
457.Cm + Ns
458.Op Cm no Ns
459.Cm search
460.Xc .
461.It Xo
462.Cm + Ns
463.Op Cm no Ns
464.Cm dnssec
465.Xc
466Request DNSSEC records be sent by setting the DNSSEC OK bit (DO) in the OPT
467record in the additional section of the query (off by default).
468.It Cm +domain Ns = Ns Ar name
469Set the search list to contain the single domain
470.Ar name ,
471as if specified in a
472.Ic domain
473directive in
474.Xr resolv.conf 5 ,
475and enable search list processing as if the
476.Cm +search
477option were given (off by default).
478.It Xo
479.Cm + Ns
480.Op Cm no Ns
481.Cm edns Ns
482.Op = Ns Ar #
483.Xc
484Use EDNS in the query (on by default).
485A version may also be specified, from 0 (the default) to 255.
486.Cm +noedns
487disables EDNS and clears the remembered version.
488.It Cm +ednsflags Ns Op = Ns Ar #
489Set the must-be-zero EDNS flags bits (Z bits)
490to the specified value (0 by default).
491Decimal, hex and octal encodings are accepted.
492Setting a named flag (e.g. DO) will silently be ignored.
493.It Xo
494.Cm + Ns
495.Op Cm no Ns
496.Cm ednsnegotiation
497.Xc
498Enable EDNS version negotiation (off by default).
499.It Xo
500.Cm + Ns
501.Op Cm no Ns
502.Cm ednsopt Ns
503.Op = Ns Ar code Ns Op : Ns Ar value
504.Xc
505Specify EDNS option with code point
506.Ar code
507and optionally payload of
508.Ar value
509as a hexadecimal string.
510.Ar code
511can be
512either an EDNS option name (for example,
513.Cm NSID
514or
515.Cm ECS ) ,
516or an arbitrary numeric value.
517.Cm +noednsopt
518clears the EDNS options to be sent.
519.It Xo
520.Cm + Ns
521.Op Cm no Ns
522.Cm expire
523.Xc
524Send an EDNS Expire option (off by default).
525.It Xo
526.Cm + Ns
527.Op Cm no Ns
528.Cm fail
529.Xc
530Do not try the next server if you receive a SERVFAIL.
531This option is on by default,
532which is the reverse of normal stub resolver behavior.
533.It Xo
534.Cm + Ns
535.Op Cm no Ns
536.Cm identify
537.Xc
538Show the IP address and port number that supplied the answer (off by default).
539This option has no effect unless the
540.Cm +short
541option is enabled.
542.It Xo
543.Cm + Ns
544.Op Cm no Ns
545.Cm idnout
546.Xc
547Convert puny code on output.
548This version of
549.Nm
550does not support IDN.
551.It Xo
552.Cm + Ns
553.Op Cm no Ns
554.Cm ignore
555.Xc
556Ignore truncation in UDP responses.
557This option is off by default, which means truncated responses
558cause retrying with TCP.
559.It Xo
560.Cm + Ns
561.Op Cm no Ns
562.Cm keepopen
563.Xc
564Keep the TCP socket open between queries and reuse it.
565This option is off by default, which means that a new TCP socket
566is created for each lookup.
567.It Xo
568.Cm + Ns
569.Op Cm no Ns
570.Cm multiline
571.Xc
572Print records like the SOA records in a verbose multi-line format with
573human-readable comments.
574This option is off by default, which means that each record is
575printed on a single line to facilitate machine parsing of the
576.Nm
577output.
578.It Cm +ndots Ns = Ns Ar #
579Set the number of dots that have to appear in
580.Ar name
581to
582.Ar #
583for it to be considered absolute.
584The default value is that defined using the ndots statement in
585.Xr resolv.conf 5 ,
586or 1 if no ndots statement is present.
587Names with fewer dots are interpreted as relative names and will be searched
588for in the domains listed in the
589.Cm search
590or
591.Cm domain
592directive in
593.Xr resolv.conf 5
594if
595.Cm +search
596is set.
597.It Xo
598.Cm + Ns
599.Op Cm no Ns
600.Cm nsid
601.Xc
602Include an EDNS name server ID request when sending a query (off by default).
603.It Xo
604.Cm + Ns
605.Op Cm no Ns
606.Cm nssearch
607.Xc
608Attempt to find the authoritative name servers for the zone
609containing the name being looked up and display the SOA record
610that each name server has for the zone (off by default).
611.It Xo
612.Cm + Ns
613.Op Cm no Ns
614.Cm onesoa
615.Xc
616Print only one (starting) SOA record when performing an
617.Cm AXFR .
618This option is off by default, which means that both the starting
619and the ending SOA records are printed.
620.It Xo
621.Cm + Ns
622.Op Cm no Ns
623.Cm opcode Ns = Ns
624.Ar #
625.Xc
626Set or restore the DNS message opcode to the specified value,
627which can be
628.Cm QUERY Pq the default ,
629.Cm IQUERY ,
630.Cm STATUS ,
631.Cm NOTIFY ,
632.Cm UPDATE ,
633or an integer number in the range from 0 to 15.
634.It Xo
635.Cm + Ns
636.Op Cm no Ns
637.Cm qr
638.Xc
639Print the query as it is sent (off by default).
640.It Xo
641.Cm + Ns
642.Op Cm no Ns
643.Cm question
644.Xc
645Print the question section of a query as a comment when an answer
646is returned (on by default).
647.It Xo
648.Cm + Ns
649.Op Cm no Ns
650.Cm rdflag
651.Xc
652A synonym for
653.Xo
654.Cm + Ns
655.Op Cm no Ns
656.Cm recurse
657.Xc .
658.It Xo
659.Cm + Ns
660.Op Cm no Ns
661.Cm recurse
662.Xc
663Set the RD (recursion desired) bit in the query (on by default).
664Recursion is automatically disabled when the
665.Cm +nssearch
666or
667.Cm +trace
668query options are used.
669.It Cm +retry Ns = Ns Ar #
670Set the number of times to retry UDP queries to server to
671.Ar # .
672The default is 2.
673Unlike
674.Cm +tries ,
675this does not include the initial query.
676.It Xo
677.Cm + Ns
678.Op Cm no Ns
679.Cm rrcomments
680.Xc
681Display per-record comments in the output (for example,
682human-readable key information about DNSKEY records).
683The default is
684.Cm +rrcomments
685if
686.Cm +multiline
687mode is active or
688.Cm +norrcomments
689otherwise.
690.It Xo
691.Cm + Ns
692.Op Cm no Ns
693.Cm search
694.Xc
695Use the search list defined by the searchlist or domain directive in
696.Xr resolv.conf 5 ,
697if any (off by default).
698\&'ndots' from
699.Xr resolv.conf 5
700(default 1), which may be overridden by
701.Cm +ndots ,
702determines if the name will be treated as relative or not and hence whether a
703search is eventually performed or not.
704.It Xo
705.Cm + Ns
706.Op Cm no Ns
707.Cm short
708.Xc
709Provide a terse answer (off by default).
710.It Xo
711.Cm + Ns
712.Op Cm no Ns
713.Cm showsearch
714.Xc
715Perform a search showing intermediate results (off by default).
716.It Xo
717.Cm + Ns
718.Op Cm no Ns
719.Cm split Ns = Ns Ar #
720.Xc
721Split long hex- or base64-formatted fields in resource records into chunks of
722.Ar #
723characters (where
724.Ar #
725is rounded up to the nearest multiple of 4).
726.Cm +nosplit
727or
728.Cm +split Ns =0
729causes fields not to be split at all.
730The default is 56 characters, or 44 characters when
731.Cm +multiline
732mode is active.
733.It Xo
734.Cm + Ns
735.Op Cm no Ns
736.Cm stats
737.Xc
738Print statistics:
739when the query was made, the size of the reply and so on (on by default).
740.It Xo
741.Cm + Ns
742.Op Cm no Ns
743.Cm subnet Ns = Ns
744.Ar addr Ns
745.Op / Ns Ar prefix
746.Xc
747Send an EDNS Client Subnet option with the specified IP address or
748network prefix (off by default).
749.Pp
750.Nm
751.Cm +subnet Ns =0.0.0.0/0,
752or simply
753.Nm
754.Cm +subnet Ns =0
755for short, sends an EDNS CLIENT-SUBNET option with an empty address and a
756source prefix-length of zero, which signals a resolver that the client's address
757information must
758.Em not
759be used when resolving this query.
760.It Xo
761.Cm + Ns
762.Op Cm no Ns
763.Cm tcp
764.Xc
765Use TCP when querying name servers (off by default).
766.Cm IXFR Ns = Ns Ar N
767queries use TCP unless it is explicitly disabled with
768.Cm +notcp .
769.Cm AXFR
770queries always use TCP.
771.It Cm +timeout Ns = Ns Ar #
772Set the timeout for a query to
773.Ar #
774seconds.
775The default is 5 seconds for UDP and 10 seconds for TCP.
776An attempt to set
777.Ar #
778to less than 1 will result in a query timeout of 1 second being applied.
779.It Xo
780.Cm + Ns
781.Op Cm no Ns
782.Cm trace
783.Xc
784Trace the delegation path from the root name servers for the name
785being looked up (off by default).
786.Pp
787When tracing is enabled,
788.Nm
789makes iterative queries to resolve the name being looked up.
790It will follow referrals from the root servers, showing the answer from each
791server that was used to resolve the lookup.
792.Pp
793If @server is also specified, it affects only the initial query for the root
794zone name servers.
795.Pp
796.Cm +dnssec
797is also set when
798.Cm +trace
799is set to better emulate the default queries from a name server.
800.It Cm +tries Ns = Ns Ar #
801Set the number of times to try UDP queries to server to
802.Ar # .
803The default is 3.
804If
805.Ar #
806is less than or equal to zero, the number of tries is silently rounded up to 1.
807.It Xo
808.Cm + Ns
809.Op Cm no Ns
810.Cm ttlid
811.Xc
812Display the TTL when printing the record (on by default).
813.It Xo
814.Cm + Ns
815.Op Cm no Ns
816.Cm vc
817.Xc
818Use TCP when querying name servers.
819This alternate syntax to
820.Xo
821.Cm + Ns
822.Op Cm no Ns
823.Cm tcp
824.Xc
825is provided for backwards compatibility.
826The "vc" stands for "virtual circuit".
827.El
828.Sh MULTIPLE QUERIES
829The BIND 9 implementation of
830.Nm
831supports specifying multiple queries on the command line (in addition to
832supporting the
833.Fl f
834batch file option).
835Each of those queries can be supplied with its own set of flags, options and
836query options.
837.Pp
838In this case, each
839.Ar query
840argument represent an individual query in the command-line syntax described
841above.
842Each consists of any of the standard options and flags, the name to be looked
843up, an optional query type and class and any query options that should be
844applied to that query.
845.Pp
846A global set of query options, which should be applied to all queries, can
847also be supplied.
848These global query options must precede the first tuple of name, class, type,
849options, flags, and query options supplied on the command line.
850Any global query options (except the
851.Xo
852.Cm + Ns
853.Op Cm no Ns
854.Cm cmd
855.Xc
856option) can be overridden by a query-specific set of query options.
857For example:
858.Bd -literal -offset indent
859dig +qr www.isc.org any -x 127.0.0.1 isc.org ns +noqr
860.Ed
861.Pp
862shows how
863.Nm
864could be used from the command line to make three lookups: an ANY query for
865www.isc.org, a reverse lookup of 127.0.0.1 and a query for the NS records of
866isc.org.
867A global query option of
868.Cm +qr
869is applied, so that
870.Nm
871shows the initial query it made for each lookup.
872The final query has a local query option of
873.Cm +noqr
874which means that
875.Nm
876will not print the initial query when it looks up the NS records for
877isc.org.
878.Sh FILES
879.Bl -tag -width Ds
880.It Pa /etc/resolv.conf
881Resolver configuration file.
882.El
883.Sh SEE ALSO
884.Xr host 1 ,
885.Xr resolv.conf 5
886.Sh STANDARDS
887.Rs
888.%A P. Mockapetris
889.%D November 1987
890.%R RFC 1035
891.%T Domain Names - Implementation and Specification
892.Re
893.Sh AUTHORS
894.An -nosplit
895.An Internet Systems Consortium, Inc .
896.Sh BUGS
897There are probably too many query options.
898