xref: /openbsd-src/usr.bin/dig/dig.1 (revision 9835a5e128ac1db1a0a5e36c27d1a17b7926c0b3)
1.\" $OpenBSD: dig.1,v 1.8 2024/12/27 09:04:48 florian Exp $
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17.Dd $Mdocdate: December 27 2024 $
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 "::".
107An optional port may be specified by appending "#<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.Cm + Ns
311.Op Cm no Ns
312.Cm aaonly .
313.It Xo
314.Cm + Ns
315.Op Cm no Ns
316.Cm aaonly
317.Xc
318Set the "aa" flag in the query (off by default).
319.It Xo
320.Cm + Ns
321.Op Cm no Ns
322.Cm additional
323.Xc
324Display the additional section of a reply (on by default).
325.It Xo
326.Cm + Ns
327.Op Cm no Ns
328.Cm adflag
329.Xc
330Set the AD (authentic data) bit in the query (on by default).
331This requests the server to return whether all of the answer and authority
332sections have all been validated as secure according to the security policy of
333the server.
334AD=1 indicates that all records have been validated as secure and the answer is
335not from an OPT-OUT range.
336AD=0 indicates that some part of the answer was insecure or not validated.
337.It Xo
338.Cm + Ns
339.Op Cm no Ns
340.Cm all
341.Xc
342Set or clear all display flags.
343.It Xo
344.Cm + Ns
345.Op Cm no Ns
346.Cm answer
347.Xc
348Display the answer section of a reply (on by default).
349.It Xo
350.Cm + Ns
351.Op Cm no Ns
352.Cm authority
353.Xc
354Display the authority section of a reply (on by default).
355.It Xo
356.Cm + Ns
357.Op Cm no Ns
358.Cm besteffort
359.Xc
360Attempt to display the contents of messages which are malformed (on by
361default).
362.It Cm +bufsize Ns = Ns Ar #
363Set the UDP message buffer size advertised using EDNS0 to
364.Ar #
365bytes.
366The maximum and minimum sizes of this buffer are 65535 and 0 respectively.
367Values outside this range are rounded up or down appropriately.
368Values other than zero will cause an EDNS query to be sent.
369.It Xo
370.Cm + Ns
371.Op Cm no Ns
372.Cm cdflag
373.Xc
374Set the CD (checking disabled) bit in the query (off by default).
375This requests the server to not perform DNSSEC validation of responses.
376.It Xo
377.Cm + Ns
378.Op Cm no Ns
379.Cm class
380.Xc
381Display the CLASS when printing the record (on by default).
382.It Xo
383.Cm + Ns
384.Op Cm no Ns
385.Cm cmd
386.Xc
387Print an initial comment identifying the version of
388.Nm
389and the query options that have been applied (on by default).
390.It Xo
391.Cm + Ns
392.Op Cm no Ns
393.Cm comments
394.Xc
395Display comment lines in the output (on by default).
396.It Xo
397.Cm + Ns
398.Op Cm no Ns
399.Cm cookie Ns
400.Op = Ns Ar value
401.Xc
402Send a COOKIE EDNS option, containing an optional
403.Ar value
404(off by default).
405Replaying a COOKIE from a previous response will allow the server to
406identify a previous client.
407.Pp
408.Cm +cookie
409is automatically set when
410.Cm +trace
411is in use, to better emulate the default queries from a name server.
412.Pp
413This option was formerly called
414.Cm + Ns
415.Op Cm no Ns
416.Cm sit
417(Server Identity Token).
418In BIND 9.10.0 through BIND 9.10.2,
419it sent the experimental option code 65001.
420This was changed to option code 10 in BIND 9.10.3 when the DNS
421COOKIE option was allocated.
422.Pp
423The
424.Cm + Ns
425.Op Cm no Ns
426.Cm sit
427option is now deprecated, but has been retained as a synonym for
428.Cm + Ns
429.Op Cm no Ns
430.Cm cookie
431for backward compatibility within the BIND 9.10 branch.
432.It Xo
433.Cm + Ns
434.Op Cm no Ns
435.Cm crypto
436.Xc
437Display cryptographic fields in DNSSEC records (on by default).
438The contents of these field are unnecessary to debug most DNSSEC validation
439failures and removing them makes it easier to see the common failures.
440When omitted they are replaced by the string "[omitted]" or in the DNSKEY case
441the key id is displayed as the replacement, e.g. "[ key id = value ]".
442.It Xo
443.Cm + Ns
444.Op Cm no Ns
445.Cm defname
446.Xc
447Deprecated, treated as a synonym for
448.Cm + Ns
449.Op Cm no Ns
450.Cm search .
451.It Xo
452.Cm + Ns
453.Op Cm no Ns
454.Cm dnssec
455.Xc
456Request DNSSEC records be sent by setting the DNSSEC OK bit (DO) in the OPT
457record in the additional section of the query (off by default).
458.It Cm +domain Ns = Ns Ar name
459Set the search list to contain the single domain
460.Ar name ,
461as if specified in a
462.Ic domain
463directive in
464.Xr resolv.conf 5 ,
465and enable search list processing as if the
466.Cm +search
467option were given (off by default).
468.It Xo
469.Cm + Ns
470.Op Cm no Ns
471.Cm edns Ns
472.Op = Ns Ar #
473.Xc
474Use EDNS in the query (on by default).
475A version may also be specified, from 0 (the default) to 255.
476.Cm +noedns
477disables EDNS and clears the remembered version.
478.It Cm +ednsflags Ns Op = Ns Ar #
479Set the must-be-zero EDNS flags bits (Z bits)
480to the specified value (0 by default).
481Decimal, hex and octal encodings are accepted.
482Setting a named flag (e.g. DO) will silently be ignored.
483.It Xo
484.Cm + Ns
485.Op Cm no Ns
486.Cm ednsnegotiation
487.Xc
488Enable EDNS version negotiation (off by default).
489.It Xo
490.Cm + Ns
491.Op Cm no Ns
492.Cm ednsopt Ns
493.Op = Ns Ar code Ns Op : Ns Ar value
494.Xc
495Specify EDNS option with code point
496.Ar code
497and optionally payload of
498.Ar value
499as a hexadecimal string.
500.Ar code
501can be
502either an EDNS option name (for example,
503.Cm NSID
504or
505.Cm ECS ) ,
506or an arbitrary numeric value.
507.Cm +noednsopt
508clears the EDNS options to be sent.
509.It Xo
510.Cm + Ns
511.Op Cm no Ns
512.Cm expire
513.Xc
514Send an EDNS Expire option (off by default).
515.It Xo
516.Cm + Ns
517.Op Cm no Ns
518.Cm fail
519.Xc
520Do not try the next server if you receive a SERVFAIL.
521This option is on by default,
522which is the reverse of normal stub resolver behavior.
523.It Xo
524.Cm + Ns
525.Op Cm no Ns
526.Cm identify
527.Xc
528Show the IP address and port number that supplied the answer (off by default).
529This option has no effect unless the
530.Cm +short
531option is enabled.
532.It Xo
533.Cm + Ns
534.Op Cm no Ns
535.Cm idnout
536.Xc
537Convert puny code on output.
538This version of
539.Nm
540does not support IDN.
541.It Xo
542.Cm + Ns
543.Op Cm no Ns
544.Cm ignore
545.Xc
546Ignore truncation in UDP responses.
547This option is off by default, which means truncated responses
548cause retrying with TCP.
549.It Xo
550.Cm + Ns
551.Op Cm no Ns
552.Cm keepopen
553.Xc
554Keep the TCP socket open between queries and reuse it.
555This option is off by default, which means that a new TCP socket
556is created for each lookup.
557.It Xo
558.Cm + Ns
559.Op Cm no Ns
560.Cm multiline
561.Xc
562Print records like the SOA records in a verbose multi-line format with
563human-readable comments.
564This option is off by default, which means that each record is
565printed on a single line to facilitate machine parsing of the
566.Nm
567output.
568.It Cm +ndots Ns = Ns Ar #
569Set the number of dots that have to appear in
570.Ar name
571to
572.Ar #
573for it to be considered absolute.
574The default value is that defined using the ndots statement in
575.Xr resolv.conf 5 ,
576or 1 if no ndots statement is present.
577Names with fewer dots are interpreted as relative names and will be searched
578for in the domains listed in the
579.Cm search
580or
581.Cm domain
582directive in
583.Xr resolv.conf 5
584if
585.Cm +search
586is set.
587.It Xo
588.Cm + Ns
589.Op Cm no Ns
590.Cm nsid
591.Xc
592Include an EDNS name server ID request when sending a query (off by default).
593.It Xo
594.Cm + Ns
595.Op Cm no Ns
596.Cm nssearch
597.Xc
598Attempt to find the authoritative name servers for the zone
599containing the name being looked up and display the SOA record
600that each name server has for the zone (off by default).
601.It Xo
602.Cm + Ns
603.Op Cm no Ns
604.Cm onesoa
605.Xc
606Print only one (starting) SOA record when performing an
607.Cm AXFR .
608This option is off by default, which means that both the starting
609and the ending SOA records are printed.
610.It Xo
611.Cm + Ns
612.Op Cm no Ns
613.Cm opcode Ns = Ns
614.Ar #
615.Xc
616Set or restore the DNS message opcode to the specified value,
617which can be
618.Cm QUERY Pq the default ,
619.Cm IQUERY ,
620.Cm STATUS ,
621.Cm NOTIFY ,
622.Cm UPDATE ,
623or an integer number in the range from 0 to 15.
624.It Xo
625.Cm + Ns
626.Op Cm no Ns
627.Cm qr
628.Xc
629Print the query as it is sent (off by default).
630.It Xo
631.Cm + Ns
632.Op Cm no Ns
633.Cm question
634.Xc
635Print the question section of a query as a comment when an answer
636is returned (on by default).
637.It Xo
638.Cm + Ns
639.Op Cm no Ns
640.Cm rdflag
641.Xc
642A synonym for
643.Cm + Ns
644.Op Cm no Ns
645.Cm recurse .
646.It Xo
647.Cm + Ns
648.Op Cm no Ns
649.Cm recurse
650.Xc
651Set the RD (recursion desired) bit in the query (on by default).
652Recursion is automatically disabled when the
653.Cm +nssearch
654or
655.Cm +trace
656query options are used.
657.It Cm +retry Ns = Ns Ar #
658Set the number of times to retry UDP queries to server to
659.Ar # .
660The default is 2.
661Unlike
662.Cm +tries ,
663this does not include the initial query.
664.It Xo
665.Cm + Ns
666.Op Cm no Ns
667.Cm rrcomments
668.Xc
669Display per-record comments in the output (for example,
670human-readable key information about DNSKEY records).
671The default is
672.Cm +rrcomments
673if
674.Cm +multiline
675mode is active or
676.Cm +norrcomments
677otherwise.
678.It Xo
679.Cm + Ns
680.Op Cm no Ns
681.Cm search
682.Xc
683Use the search list defined by the searchlist or domain directive in
684.Xr resolv.conf 5 ,
685if any (off by default).
686\&'ndots' from
687.Xr resolv.conf 5
688(default 1), which may be overridden by
689.Cm +ndots ,
690determines if the name will be treated as relative or not and hence whether a
691search is eventually performed or not.
692.It Xo
693.Cm + Ns
694.Op Cm no Ns
695.Cm short
696.Xc
697Provide a terse answer (off by default).
698.It Xo
699.Cm + Ns
700.Op Cm no Ns
701.Cm showsearch
702.Xc
703Perform a search showing intermediate results (off by default).
704.It Xo
705.Cm + Ns
706.Op Cm no Ns
707.Cm split Ns = Ns Ar #
708.Xc
709Split long hex- or base64-formatted fields in resource records into chunks of
710.Ar #
711characters (where
712.Ar #
713is rounded up to the nearest multiple of 4).
714.Cm +nosplit
715or
716.Cm +split Ns =0
717causes fields not to be split at all.
718The default is 56 characters, or 44 characters when
719.Cm +multiline
720mode is active.
721.It Xo
722.Cm + Ns
723.Op Cm no Ns
724.Cm stats
725.Xc
726Print statistics:
727when the query was made, the size of the reply and so on (on by default).
728.It Xo
729.Cm + Ns
730.Op Cm no Ns
731.Cm subnet Ns = Ns
732.Ar addr Ns
733.Op / Ns Ar prefix
734.Xc
735Send an EDNS Client Subnet option with the specified IP address or
736network prefix (off by default).
737.Pp
738.Nm
739.Cm +subnet Ns =0.0.0.0/0,
740or simply
741.Nm
742.Cm +subnet Ns =0
743for short, sends an EDNS CLIENT-SUBNET option with an empty address and a
744source prefix-length of zero, which signals a resolver that the client's address
745information must
746.Em not
747be used when resolving this query.
748.It Xo
749.Cm + Ns
750.Op Cm no Ns
751.Cm tcp
752.Xc
753Use TCP when querying name servers (off by default).
754.Cm IXFR Ns = Ns Ar N
755queries use TCP unless it is explicitly disabled with
756.Cm +notcp .
757.Cm AXFR
758queries always use TCP.
759.It Cm +timeout Ns = Ns Ar #
760Set the timeout for a query to
761.Ar #
762seconds.
763The default is 5 seconds for UDP and 10 seconds for TCP.
764An attempt to set
765.Ar #
766to less than 1 will result in a query timeout of 1 second being applied.
767.It Xo
768.Cm + Ns
769.Op Cm no Ns
770.Cm trace
771.Xc
772Trace the delegation path from the root name servers for the name
773being looked up (off by default).
774.Pp
775When tracing is enabled,
776.Nm
777makes iterative queries to resolve the name being looked up.
778It will follow referrals from the root servers, showing the answer from each
779server that was used to resolve the lookup.
780.Pp
781If @server is also specified, it affects only the initial query for the root
782zone name servers.
783.Pp
784.Cm +dnssec
785is also set when
786.Cm +trace
787is set to better emulate the default queries from a name server.
788.It Cm +tries Ns = Ns Ar #
789Set the number of times to try UDP queries to server to
790.Ar # .
791The default is 3.
792If
793.Ar #
794is less than or equal to zero, the number of tries is silently rounded up to 1.
795.It Xo
796.Cm + Ns
797.Op Cm no Ns
798.Cm ttlid
799.Xc
800Display the TTL when printing the record (on by default).
801.It Xo
802.Cm + Ns
803.Op Cm no Ns
804.Cm vc
805.Xc
806Use TCP when querying name servers.
807This alternate syntax to
808.Cm + Ns
809.Op Cm no Ns
810.Cm tcp
811is provided for backwards compatibility.
812The "vc" stands for "virtual circuit".
813.It Xo
814.Cm + Ns
815.Op Cm no Ns
816.Cm zoneversion
817.Xc
818Include an EDNS zone version request when sending a query (off by default).
819.El
820.Sh MULTIPLE QUERIES
821The BIND 9 implementation of
822.Nm
823supports specifying multiple queries on the command line (in addition to
824supporting the
825.Fl f
826batch file option).
827Each of those queries can be supplied with its own set of flags, options and
828query options.
829.Pp
830In this case, each
831.Ar query
832argument represent an individual query in the command-line syntax described
833above.
834Each consists of any of the standard options and flags, the name to be looked
835up, an optional query type and class and any query options that should be
836applied to that query.
837.Pp
838A global set of query options, which should be applied to all queries, can
839also be supplied.
840These global query options must precede the first tuple of name, class, type,
841options, flags, and query options supplied on the command line.
842Any global query options (except the
843.Cm + Ns
844.Op Cm no Ns
845.Cm cmd
846option) can be overridden by a query-specific set of query options.
847For example:
848.Bd -literal -offset indent
849dig +qr www.isc.org any -x 127.0.0.1 isc.org ns +noqr
850.Ed
851.Pp
852shows how
853.Nm
854could be used from the command line to make three lookups: an ANY query for
855www.isc.org, a reverse lookup of 127.0.0.1 and a query for the NS records of
856isc.org.
857A global query option of
858.Cm +qr
859is applied, so that
860.Nm
861shows the initial query it made for each lookup.
862The final query has a local query option of
863.Cm +noqr
864which means that
865.Nm
866will not print the initial query when it looks up the NS records for
867isc.org.
868.Sh FILES
869.Bl -tag -width Ds
870.It Pa /etc/resolv.conf
871Resolver configuration file.
872.El
873.Sh SEE ALSO
874.Xr host 1 ,
875.Xr resolv.conf 5
876.Sh STANDARDS
877.Rs
878.%A P. Mockapetris
879.%D November 1987
880.%R RFC 1035
881.%T Domain Names - Implementation and Specification
882.Re
883.Sh AUTHORS
884.An -nosplit
885.An Internet Systems Consortium, Inc .
886.Sh BUGS
887There are probably too many query options.
888