dig - DNS lookup utility
dig [ @server ] [ -b address ] [ -c class ] [ -f file-
name ] [ -k filename ] [ -p port# ] [ -t type ] [ -x
addr ] [ -y name:key ] [ 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 BIND9 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 arguements.
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 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.
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 file-
name. The file contains a number of queries, one per line.
Each entry in the file should be organised in the same way
they would be presented as queries to dig using the command-line
interface.
If a non-standard port number is to be queried, the -p
option is used. port# is the port number that dig will
send its queries instead of the standard DNS port number
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.
The -t option sets the query type to type. It can be any
valid query type which is supported in BIND9. The default
query type "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.
Reverse lookups - mapping addresses to names - are simplified
by the -x option. addr is an IPv4 address in dotteddecimal
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 the IP6.ARPA
domain and binary labels as defined in RFC2874. To use the
older RFC1886 method using the IP6.INT domain and "nibble"
labels, specify the -n (nibble) option.
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; 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 behaviour 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]defname
Deprecated, treated as a synonym for +[no]search
+[no]aaonly
This option does nothing. It is provided for compatibility
with old versions of dig where it set an
unimplemented resolver flag.
+[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]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 behaviour 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 time out 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 retry UDP queries to
server to T instead of the default, 3. If T is less
than or equal to zero, the number of retries is
silently rounded up to 1.
+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.
+[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
behaviour.
+[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.
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.
/etc/resolv.conf
${HOME}/.digrc
host(1), named(8), RFC1035.
There are probably too many query options.
BIND9 Jun 30, 2000 7 [ Back ] |
