--- name: "dig" section: "1bind" platform: "linux" package: "bind" version: "4.9.7-2" release: "Debian 1.3 (Bo)" platforms: ["linux"] url: "https://new.carta.tech/dig/1bind" --- # dig(1bind) send domain name query packets to name servers ## NAME dig - send domain name query packets to name servers ## SYNOPSIS **dig** \[*@server*\] *domain* \[*\*\] \[*\*\] \[*+\*\] \[*-\*\] \[*%comment*\] ## DESCRIPTION *Dig* (domain information groper) is a flexible command line tool which can be used to gather information from the Domain Name System servers. *Dig* has two modes: simple interactive mode which makes a single query, and batch which executes a query for each in a list of several query lines. All query options are accessible from the command line. The usual simple use of *dig* will take the form: dig @server domain query-type query-class where: - *server* may be either a domain name or a dot-notation Internet address. If this optional field is omitted, *dig* will attempt to use the default name server for your machine. **Note:** If a domain name is specified, this will be resolved using the domain name system resolver (i.e., BIND). If your system does not support DNS, you may *have* to specify a dot-notation address. Alternatively, if there is a server at your disposal somewhere, all that is required is that /etc/resolv.conf be present and indicate where the default name servers reside, so that *server* itself can be resolved. See [*resolver*(5)](/resolver/5.md) for information on /etc/resolv.conf. (WARNING: Changing /etc/resolv.conf will affect the standard resolver library and potentially several programs which use it.) As an option, the user may set the environment variable LOCALRES to name a file which is to be used instead of /etc/resolv.conf (LOCALRES is specific to the *dig* resolver and not referenced by the standard resolver). If the LOCALRES variable is not set or the file is not readable then /etc/resolv.conf will be used. - *domain* is the domain name for which you are requesting information. See OPTIONS \[-x\] for convenient way to specify inverse address query. - *query-type* is the type of information (DNS query type) that you are requesting. If omitted, the default is "a" (T\_A = address). The following types are recognized: ``` a T_A network address any T_ANY all/any information about specified domain mx T_MX mail exchanger for the domain ns T_NS name servers soa T_SOA zone of authority record hinfo T_HINFO host information axfr T_AXFR zone transfer (must ask an authoritative server) txt T_TXT arbitrary number of strings ``` (See RFC 1035 for the complete list.) - *query-class* is the network class requested in the query. If omitted, the default is "in" (C\_IN = Internet). The following classes are recognized: ``` in C_IN Internet class domain any C_ANY all/any class information ``` (See RFC 1035 for the complete list.) **Note:** "Any" can be used to specify a class and/or a type of query. *Dig* will parse the first occurrence of "any" to mean query-type = T\_ANY. To specify query-class = C\_ANY you must either specify "any" twice, or set query-class using "-c" option (see below). ## OTHER OPTIONS - %ignored-comment "%" is used to included an argument that is simply not parsed. This may be useful if running *dig* in batch mode. Instead of resolving every @server-domain-name in a list of queries, you can avoid the overhead of doing so, and still have the domain name on the command line as a reference. Example: dig @128.9.0.32 %venera.isi.edu mx isi.edu - \-\ "-" is used to specify an option which effects the operation of *dig*. The following options are currently available (although not guaranteed to be useful): - \-x *dot-notation-address* Convenient form to specify inverse address mapping. Instead of "dig 32.0.9.128.in-addr.arpa" one can simply "dig -x 128.9.0.32". - \-f *file* File for *dig* batch mode. The file contains a list of query specifications (*dig* command lines) which are to be executed successively. Lines beginning with ';', '#', or '\\n' are ignored. Other options may still appear on command line, and will be in effect for each batch query. - \-T *time* Time in seconds between start of successive queries when running in batch mode. Can be used to keep two or more batch *dig* commands running roughly in sync. Default is zero. - \-p *port* Port number. Query a name server listening to a non-standard port number. Default is 53. - \-P\[*ping-string*\] After query returns, execute a [*ping*(8)](/ping/8.md) command for response time comparison. This rather inelegantly makes a call to the shell. The last three lines of statistics is printed for the command: ping -s server\_name 56 3 If the optional "ping string" is present, it replaces "ping -s" in the shell command. - \-t *query-type* Specify type of query. May specify either an integer value to be included in the type field or use the abbreviated mnemonic as discussed above (i.e., mx = T\_MX). - \-c *query-class* Specify class of query. May specify either an integer value to be included in the class field or use the abbreviated mnemonic as discussed above (i.e., in = C\_IN). - \-envsav This flag specifies that the *dig* environment (defaults, print options, etc.), after all of the arguments are parsed, should be saved to a file to become the default environment. Useful if you do not like the standard set of defaults and do not desire to include a large number of options each time *dig* is used. The environment consists of resolver state variable flags, timeout, and retries as well as the flags detailing *dig* output (see below). If the shell environment variable LOCALDEF is set to the name of a file, this is where the default *dig* environment is saved. If not, the file "DiG.env" is created in the current working directory. **Note:** LOCALDEF is specific to the *dig* resolver, and will not affect operation of the standard resolver library. Each time *dig* is executed, it looks for "./DiG.env" or the file specified by the shell environment variable LOCALDEF. If such file exists and is readable, then the environment is restored from this file before any arguments are parsed. - \-envset This flag only affects batch query runs. When "-envset" is specified on a line in a *dig* batch file, the *dig* environment after the arguments are parsed, becomes the default environment for the duration of the batch file, or until the next line which specifies "-envset". - \-\[no\]stick This flag only affects batch query runs. It specifies that the *dig* environment (as read initially or set by "-envset" switch) is to be restored before each query (line) in a *dig* batch file. The default "-nostick" means that the *dig* environment does not stick, hence options specified on a single line in a *dig* batch file will remain in effect for subsequent lines (i.e. they are not restored to the "sticky" default). - \+\ "+" is used to specify an option to be changed in the query packet or to change *dig* output specifics. Many of these are the same parameters accepted by [*nslookup*(8)](/nslookup/8.md). If an option requires a parameter, the form is as follows: \+keyword\[=value\] Most keywords can be abbreviated. Parsing of the "+" options is very simplistic — a value must not be separated from its keyword by white space. The following keywords are currently available: ``` Keyword Abbrev. Meaning [default] [no]debug (deb) turn on/off debugging mode [deb] [no]d2 turn on/off extra debugging mode [nod2] [no]recurse (rec) use/don't use recursive lookup [rec] retry=# (ret) set number of retries to # [4] time=# (ti) set timeout length to # seconds [4] [no]ko keep open option (implies vc) [noko] [no]vc use/don't use virtual circuit [novc] [no]defname (def) use/don't use default domain name [def] [no]search (sea) use/don't use domain search list [sea] domain=NAME (do) set default domain name to NAME [no]ignore (i) ignore/don't ignore trunc. errors [noi] [no]primary (pr) use/don't use primary server [nopr] [no]aaonly (aa) authoritative query only flag [noaa] [no]sort (sor) sort resource records [nosor] [no]cmd echo parsed arguments [cmd] [no]stats (st) print query statistics [st] [no]Header (H) print basic header [H] [no]header (he) print header flags [he] [no]ttlid (tt) print TTLs [tt] [no]cl print class info [nocl] [no]qr print outgoing query [noqr] [no]reply (rep) print reply [rep] [no]ques (qu) print question section [qu] [no]answer (an) print answer section [an] [no]author (au) print authoritative section [au] [no]addit (ad) print additional section [ad] pfdef set to default print flags pfmin set to minimal default print flags pfset=# set print flags to # (# can be hex/octal/decimal) pfand=# bitwise and print flags with # pfor=# bitwise or print flags with # ``` The retry and time options affect the retransmission strategy used by resolver library when sending datagram queries. The algorithm is as follows: ``` for i = 0 to retry - 1 for j = 1 to num_servers send_query wait((time * (2**i)) / num_servers) end end ``` (Note: *dig* always uses a value of 1 for num\_servers.) ## DETAILS *Dig* once required a slightly modified version of the BIND [*resolver*(3)](/resolver/3.md) library. BIND's resolver has (as of BIND 4.9) been augmented to work properly with *Dig*. Essentially, *Dig* is a straight-forward (albeit not pretty) effort of parsing arguments and setting appropriate parameters. *Dig* uses resolver routines res\_init(), res\_mkquery(), res\_send() as well as accessing \_res structure. ## FILES /etc/resolv.conf initial domain name and name server ./DiG.env default save file for default options\ \ addresses ## ENVIRONMENT LOCALRES file to use in place of /etc/resolv.conf\ LOCALDEF default environment file ## AUTHOR Steve Hotz hotz@isi.edu ## ACKNOWLEDGMENTS *Dig* uses functions from [*nslookup*(8)](/nslookup/8.md) authored by Andrew Cherenson. ## BUGS *Dig* has a serious case of "creeping featurism" -- the result of considering several potential uses during it's development. It would probably benefit from a rigorous diet. Similarly, the print flags and granularity of the items they specify make evident their rather ad hoc genesis. *Dig* does not consistently exit nicely (with appropriate status) when a problem occurs somewhere in the resolver (NOTE: most of the common exit cases are handled). This is particularly annoying when running in batch mode. If it exits abnormally (and is not caught), the entire batch aborts; when such an event is trapped, *dig* simply continues with the next query. ## SEE ALSO [named(8)](/named/8.md), [resolver(3)](/resolver/3.md), [resolver(5)](/resolver/5.md), [nslookup(8)](/nslookup/8.md)