 |
Index for
Section 1 |
|
 |
Alphabetical
listing for D |
|
 |
Bottom of
page |
|
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 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.
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 supplied, 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 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 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 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.
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 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.
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 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.
FILES
/etc/resolv.conf
${HOME}/.digrc
SEE ALSO
host(1), named(8), dnssec-keygen(8), RFC1035.
BUGS
There are probably too many query options.
|
Index for
Section 1 |
|
|
Alphabetical
listing for D |
|
 |
Top of
page |
|