2014-02-12ISCInternet Systems Consortium, Inc.dig1BIND9digDNS lookup utility20042005200620072008200920102011201320142015Internet Systems Consortium, Inc. ("ISC")2000200120022003Internet Software Consortium.dig@servernametypeclassqueryoptdigdigglobal-queryoptqueryDESCRIPTIONdig
(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 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. If no usable server addresses
are found, dig will send the query to the local
host.
When no command line arguments or options are given,
dig 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
domain names. Either use the and
options to specify the type and class,
use the the 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 or
options are in use, then
only addresses for the corresponding transport
will be tried. If no usable addresses are found,
dig will send 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 will perform a lookup for an
A record.
OPTIONS-4
Use IPv4 only.
-6
Use IPv6 only.
-b address#port
Set 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
Set the query class. The
default class is IN; other classes
are HS for Hesiod records or CH for Chaosnet records.
-f file
Batch mode: 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 they would be
presented as queries to
dig using the command-line interface.
-i
Do reverse IPv6 lookups using the obsolete RFC1886 IP6.INT
domain, which is no longer in use. Obsolete bit string
label queries (RFC2874) are not attempted.
-k keyfile
Sign queries using TSIG using a key read from the given file.
Key files can be generated using
tsig-keygen8.
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.
-m
Enable memory usage debugging.
-p port
Send the query to a non-standard port on the server,
instead of the defaut port 53. This option would be used
to test a name server that has been configured to listen
for queries on a non-standard port number.
-q name
The domain name to query. This is useful to distinguish
the name from other arguments.
-t type
The resource record type to query. It can be any valid query type
which is
supported in BIND 9. The default query type is "A", unless the
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 will contain the changes
made to the zone since the serial number in the zone's SOA
record was
N.
-v
Print the version number and exit.
-x addr
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 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 (but see also the
option).
-y hmac:keyname:secret
Sign 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.
NOTE: You should use the option and
avoid the option, because
with 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 OPTIONSdig
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 .
Keywords may be abbreviated, provided the abbreviation is
unambiguous; for example, +cd is equivalent
to +cdflag.
The query options are:
A synonym for +[no]aaonly.
Sets the "aa" flag in the query.
Display [do not display] the additional section of a
reply. The default is to display it.
Set [do 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 all
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 indicate that some part
of the answer was insecure or not validated. This
bit is set by default.
Set or clear all display flags.
Display [do not display] the answer section of a
reply. The default is to display it.
Display [do not display] the authority section of a
reply. The default is to display it.
Attempt to display the contents of messages which are
malformed. The default is to not display malformed
answers.
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.
Set [do not set] the CD (checking disabled) bit in
the query. This requests the server to not perform
DNSSEC validation of responses.
Display [do not display] the CLASS when printing the
record.
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.
Toggle the display of comment lines in the output.
The default is to print comments.
Deprecated, treated as a synonym for
+[no]search
Requests DNSSEC records be sent by setting the DNSSEC
OK bit (DO) in the OPT record in the additional section
of the query.
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.
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.
clears the remembered EDNS version. EDNS is set to
0 by default.
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.
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.
Ignore truncation in UDP responses instead of retrying
with TCP. By default, TCP retries are performed.
Keep the TCP socket open between queries and reuse
it rather than creating a new TCP socket for each
lookup. The default is .
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.
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
or directive in
/etc/resolv.conf if
is set.
Include an EDNS name server ID request when sending
a query.
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.
Print only one (starting) SOA record when performing
an AXFR. The default is to print both the starting
and ending SOA records.
Print [do not print] the query as it is sent. By
default, the query is not printed.
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.
A synonym for +[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.
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.
Toggle 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.
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.
'ndots' from resolv.conf (default 1)
which may be overridden by +ndots
determines if the name will be treated as relative
or not and hence whether a search is eventually
performed or not.
Provide a terse answer. The default is to print the
answer in a verbose form.
Perform [do not perform] a search showing intermediate
results.
Chase DNSSEC signature chains. Requires dig be
compiled with -DDIG_SIGCHASE.
Split 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.
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.
Use [do not use] TCP when querying name servers. The
default behavior is to use UDP unless an
ixfr=N query is requested, in which
case the default is TCP. AXFR queries always use
TCP.
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.
When chasing DNSSEC signature chains perform a top-down
validation. Requires dig be compiled with -DDIG_SIGCHASE.
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.
If @server is also specified, it affects only the
initial query for the root zone name servers.
+dnssec is also set when +trace
is set to better emulate the default queries from a
nameserver.
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.
Specifies a file containing trusted keys to be used
with . 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.
Display [do not display] the TTL when printing the
record.
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".
MULTIPLE QUERIES
The BIND 9 implementation of dig
supports
specifying multiple queries on the command line (in addition to
supporting the 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 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.
IDN SUPPORT
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.
FILES/etc/resolv.conf${HOME}/.digrcSEE ALSOhost1,
named8,
dnssec-keygen8,
RFC1035.
BUGS
There are probably too many query options.