dig
DIG(1) DIG(1)
NAME
dig - DNS lookup utility
SYNOPSIS
dig [ @server ] [ -b address ] [ -c class ] [ -f filename ] [ -k
filename ] [ -p port# ] [ -t type ] [ -x addr ] [ -y name:key ] [
name ] [ type ] [ class ] [ queryopt... ]
dig [ -h ]
dig [ global-queryopt... ] [ query... ]
DESCRIPTION
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 admin-
istrators use dig to troubleshoot DNS problems because of its flexibil-
ity, 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 implementa-
tion 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).
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 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 sup-
plied, dig will perform a lookup for an A record.
OPTIONS
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 filename. 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 trans-
fer can be requested by specifying a type of AXFR. When an incremental
zone transfer (IXFR) is required, type is set to ixfr=N. The incremen-
tal 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 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 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 transac-
tion 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-key-
gen(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.
QUERY OPTIONS
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 strate-
gies.
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 +key-
word=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 compatibilty 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 pro-
vided 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]recursive
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 iden-
tifying 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 sup-
plied 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 for-
mat 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 the OPT record in the additional section of the
query.
MULTIPLE QUERIES
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 stan-
dard 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.
FILES
/etc/resolv.conf
SEE ALSO
host(1), named(8), dnssec-keygen(8), RFC1035.
BUGS
There are probably too many query options.
BIND9 Jun 30, 2000 DIG(1)
