dig [@server] [-b address]
[-c class]
[-f filename]
[-k filename]
[-q name] [-t type]
[-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.
When no command line arguments or options are given, 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
domains names. Either use the -t and -c options to specify the
type and class or 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:
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 and queries the name servers listed there. 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 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 "::".
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 -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
useful do distinguish the name from other arguments.
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]tcp
Use [do not use] TCP when querying name servers. The
default behavior is to use UDP unless an AXFR or IXFR query is requested, in
which case a TCP connection is used.
+[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".
+[no]ignore
Ignore truncation in UDP responses instead of retrying
with TCP. By default, TCP retries are performed.
+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]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]showsearch
Perform [do not perform] a search showing intermediate
results.
+[no]defname
Deprecated, treated as a synonym for
+[no]search
+[no]aaonly
Sets the "aa" flag in the query.
+[no]aaflag
A synonym for +[no]aaonly.
+[no]adflag
Set [do not set] the AD (authentic data) bit in the
query. The AD bit currently has a standard meaning only in responses, not in
queries, but the ability to set the bit in the query is provided for
completeness.
+[no]cdflag
Set [do not set] the CD (checking disabled) bit in the
query. This requests the server to not perform DNSSEC validation of
responses.
+[no]cl
Display [do not display] the CLASS when printing the
record.
+[no]ttlid
Display [do not display] the TTL when printing the
record.
+[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.
+[no]nssearch
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.
+[no]trace
Toggle 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.
+[no]cmd
Toggles 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]short
Provide a terse answer. The default is to print the
answer in a verbose form.
+[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]comments
Toggle the display of comment lines in the output. The
default is to print comments.
+[no]stats
This 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]qr
Print [do not print] the query as it is sent. By default,
the query is not printed.
+[no]question
Print [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]answer
Display [do not display] the answer section of a reply.
The default is to display it.
+[no]authority
Display [do not display] the authority section of a
reply. The default is to display it.
+[no]additional
Display [do not display] the additional section of a
reply. The default is to display it.
+[no]all
Set or clear all display flags.
+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.
+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.
+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.
+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.
+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.
+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.
+[no]multiline
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.
+[no]fail
Do 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]besteffort
Attempt to display the contents of messages which are
malformed. The default is to not display malformed answers.
+[no]dnssec
Requests DNSSEC records be sent by setting the DNSSEC OK
bit (DO) in the OPT record in the additional section of the query.
+[no]sigchase
Chase DNSSEC signature chains. Requires dig be compiled
with -DDIG_SIGCHASE.
+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]topdown
When chasing DNSSEC signature chains perform a top-down
validation. Requires dig be compiled with -DDIG_SIGCHASE.
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.
/etc/resolv.conf
${HOME}/.digrc
host(1), named(8), dnssec-keygen(8), RFC1035.
There are probably too many query options.
Copyright © 2004-2007 Internet Systems Consortium, Inc. ("ISC")
Copyright © 2000-2003 Internet Software Consortium.
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