kdig – Advanced DNS lookup utility¶
Description¶
This utility sends one or more DNS queries to a nameserver. Each query can have individual settings, or it can be specified globally via common-settings, which must precede query specification.
Parameters¶
- query
name | -q name | -x address | -G tapfile
- common-settings, settings
[query_class] [query_type] [@server]… [options]
- name
Is a domain name that is to be looked up.
- server
Is a domain name or an IPv4 or IPv6 address of the nameserver to send a query to. An additional port can be specified using address:port ([address]:port for IPv6 address), address@port, or address#port notation. If no server is specified, the servers from
/etc/resolv.confare used.
If no arguments are provided, kdig sends NS query for the root zone.
Query classes¶
A query_class can be either a DNS class name (IN, CH) or generic class specification CLASSXXXXX where XXXXX is a corresponding decimal class number. The default query class is IN.
Query types¶
A query_type can be either a DNS resource record type (A, AAAA, NS, SOA, DNSKEY, ANY, etc.) or one of the following:
- TYPEXXXXX
Generic query type specification where XXXXX is a corresponding decimal type number.
- AXFR
Full zone transfer request.
- IXFR=serial
Incremental zone transfer request for specified SOA serial number (i.e. all zone updates since the specified zone version are to be returned).
- NOTIFY=serial
Notify message with a SOA serial hint specified.
- NOTIFY
Notify message with a SOA serial hint unspecified.
The default query type is A.
Options¶
- -4
Use the IPv4 protocol only.
- -6
Use the IPv6 protocol only.
- -b address
Set the source IP address of the query to address. The address must be a valid address for local interface or :: or 0.0.0.0. An optional port can be specified in the same format as the server value.
- -c class
An explicit query_class specification. See possible values above.
- -d
Enable debug messages.
- -h, –help
Print the program help.
- -k keyfile
Use the TSIG key stored in a file keyfile to authenticate the request. The file must contain the key in the same format as accepted by the -y option.
- -p port
Set the nameserver port number or service name to send a query to. The default port is 53.
- -q name
Set the query name. An explicit variant of name specification. If no name is provided, empty question section is set.
- -t type
An explicit query_type specification. See possible values above.
- -V, –version
Print the program version.
- -x address
Send a reverse (PTR) query for IPv4 or IPv6 address. The correct name, class and type is set automatically.
- -y [alg:]name:key
Use the TSIG key named name to authenticate the request. The alg part specifies the algorithm (the default is hmac-sha256) and key specifies the shared secret encoded in Base64.
- -E tapfile
Export a dnstap trace of the query and response messages received to the file tapfile.
- -G tapfile
Generate message output from a previously saved dnstap file tapfile.
- +[no]multiline
Wrap long records to more lines and improve human readability.
- +[no]short
Show record data only.
- +[no]generic
Use the generic representation format when printing resource record types and data.
- +[no]crypto
Display the DNSSEC keys and signatures values in base64, instead of omitting them.
- +[no]aaflag
Set the AA flag.
- +[no]tcflag
Set the TC flag.
- +[no]rdflag
Set the RD flag.
- +[no]recurse
Same as +[no]rdflag
- +[no]raflag
Set the RA flag.
- +[no]zflag
Set the zero flag bit.
- +[no]adflag
Set the AD flag.
- +[no]cdflag
Set the CD flag.
- +[no]dnssec
Set the DO flag.
- +[no]all
Show all packet sections.
- +[no]qr
Show the query packet.
- +[no]header
Show the packet header.
- +[no]comments
Show commented section names.
- +[no]opt
Show the EDNS pseudosection.
- +[no]opttext
Try to show unknown EDNS options as text.
- +[no]question
Show the question section.
- +[no]answer
Show the answer section.
- +[no]authority
Show the authority section.
- +[no]additional
Show the additional section.
- +[no]tsig
Show the TSIG pseudosection.
- +[no]stats
Show trailing packet statistics.
- +[no]class
Show the DNS class.
- +[no]ttl
Show the TTL value.
- +[no]tcp
Use the TCP protocol (default is UDP for standard query and TCP for AXFR/IXFR).
- +[no]fastopen
Use TCP Fast Open (default with TCP).
- +[no]ignore
Don’t use TCP automatically if a truncated reply is received.
- +[no]tls
Use TLS with the Opportunistic privacy profile (RFC 7858#section-4.1).
- +[no]tls-ca[=FILE]
Use TLS with a certificate validation. Certification authority certificates are loaded from the specified PEM file (default is system certificate storage if no argument is provided). Can be specified multiple times. If the +tls-hostname option is not provided, the name of the target server (if specified) is used for strict authentication.
- +[no]tls-pin=BASE64
Use TLS with the Out-of-Band key-pinned privacy profile (RFC 7858#section-4.2). The PIN must be a Base64 encoded SHA-256 hash of the X.509 SubjectPublicKeyInfo. Can be specified multiple times.
- +[no]tls-hostname=STR
Use TLS with a remote server hostname check.
- +[no]tls-sni=STR
Use TLS with a Server Name Indication.
- +[no]tls-keyfile=FILE
Use TLS with a client keyfile.
- +[no]tls-certfile=FILE
Use TLS with a client certfile.
- +[no]tls-ocsp-stapling[=H]
Use TLS with a valid stapled OCSP response for the server certificate (%u or specify hours). OCSP responses older than the specified period are considered invalid.
- +[no]https[=URL]
Use HTTPS (DNS-over-HTTPS) in wire format (RFC 1035#section-4.2.1). It is also possible to specify URL=[authority][/path] where request will be send. Authority might also be specified as server name (parameter @). Library libnghttp2 is required.
- +[no]https-get
Use HTTPS with HTTP/GET method instead of the default HTTP/POST method. Library libnghttp2 is required.
- +[no]nsid
Request the nameserver identifier (NSID).
- +[no]bufsize=B
Set EDNS buffer size in bytes (default is 4096 bytes).
- +[no]padding[=B]
Use EDNS(0) padding option to pad queries, optionally to a specific size. The default is to pad queries with a sensible amount when using +tls, and not to pad at all when queries are sent without TLS. With no argument (i.e., just +padding) pad every query with a sensible amount regardless of the use of TLS. With +nopadding, never pad.
- +[no]alignment[=B]
Align the query to B-byte-block message using the EDNS(0) padding option (default is no or 128 if no argument is specified).
- +[no]subnet=SUBN
Set EDNS(0) client subnet SUBN=addr/prefix.
- +[no]edns[=N]
Use EDNS version (default is 0).
- +[no]timeout=T
Set the wait-for-reply interval in seconds (default is 5 seconds). This timeout applies to each query attempt. An attempt to set T to less than 1 will result in a query timeout of 1 second being applied.
- +[no]retry=N
Set the number (>=0) of UDP retries (default is 2). This doesn’t apply to AXFR/IXFR.
- +[no]cookie=HEX
Attach EDNS(0) cookie to the query.
- +[no]badcookie
Repeat a query with the correct cookie.
- +[no]ednsopt[=CODE[:HEX]]
Send custom EDNS option. The CODE is EDNS option code in decimal, HEX is an optional hex encoded string to use as EDNS option value. This argument can be used multiple times. +noednsopt clears all EDNS options specified by +ednsopt.
- +noidn
Disable the IDN transformation to ASCII and vice versa. IDN support depends on libidn availability during project building! If used in common-settings, all IDN transformations are disabled. If used in the individual query settings, transformation from ASCII is disabled on output for the particular query. Note that IDN transformation does not preserve domain name letter case.
Notes¶
Options -k and -y can not be used simultaneously.
Dnssec-keygen keyfile format is not supported. Use keymgr(8) instead.
Exit values¶
Exit status of 0 means successful operation. Any other exit status indicates an error.
Examples¶
Get A records for example.com:
$ kdig example.com APerform AXFR for zone example.com from the server 192.0.2.1:
$ kdig example.com -t AXFR @192.0.2.1Get A records for example.com from 192.0.2.1 and reverse lookup for address 2001:DB8::1 from 192.0.2.2. Both using the TCP protocol:
$ kdig +tcp example.com -t A @192.0.2.1 -x 2001:DB8::1 @192.0.2.2
Get SOA record for example.com, use TLS, use system certificates, check for specified hostname, check for certificate pin, and print additional debug info:
$ kdig -d @185.49.141.38 +tls-ca +tls-host=getdnsapi.net \ +tls-pin=foxZRnIh9gZpWnl+zEiKa0EJ2rdCGroMWm02gaxSc9S= soa example.com
DNS over HTTPS examples (various DoH implementations):
$ kdig @1.1.1.1 +https example.com. $ kdig @193.17.47.1 +https=/doh example.com. $ kdig @8.8.4.4 +https +https-get example.com.
Files¶
/etc/resolv.conf
See Also¶
khost(1), knsupdate(1), keymgr(8).
