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Man Dig :
DIG(1) BIND9 DIG(1)
NAME
dig - DNS lookup utility
SYNOPSIS
dig [@server] [-b address] [-c class] [-f filename] [-k filename] [-p port#] [-q name]
[-t type] [-x addr] [-y [hmac:]name:key] [-4] [-6] [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
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.
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 or "0.0.0.0" or "::". An optional port may be
specified by appending "#<port>"
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.
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 -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.
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 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.
+[no]nsid
Include an EDNS name server ID request when sending a 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.
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}/.digrc
SEE ALSO
host(1), named(8), dnssec-keygen(8), RFC1035.
BUGS
There are probably too many query options.
COPYRIGHT
Copyright ? 2004-2008 Internet Systems Consortium, Inc. ("ISC")
Copyright ? 2000-2003 Internet Software Consortium.
BIND9 Jun 30, 2000 DIG(1)
[ 本帖最后由 kof2002 于 2008-10-9 12:16 编辑 ] |
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