dig (english) Cheat Sheet

A cheat sheet in English by TME520

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PRs

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Syntax

dig [@server] [-b address] [-c class] [-f filename] [-k filename] [-m] [-p port#] [-q name] [-t type] [-x addr] [-y [hmac:]name:key] [-4] [-6] [name] [type] [class] [queryopt...]

Config

Tired of always typing the same options ? Create a Run Control file for dig.

vi $HOME/.digrc

$ cat $HOME/.digrc
+noall +answer

List specific types of RRs (Resource Records)

List address records	`dig -t A tme520.net`
List aliases	`dig -t CNAME tme520.net`
Find who manages a domain	`dig -t SOA tme520.net`
List mail servers	`dig tme520.net MX`
List name servers	`dig tme520.net NS`
List any type of Resource Record	`dig tme520.net ANY`

There are about 40 DNS Resources Records types, but you only have to know 5 of them:

- A : Address record (IPv4); AAAA for IPv6,
- CNAME : Canonical Name. Aliases to A or AAAA records,
- SOA : Start Of Authority: primary name server, email of the domain admin, domain serial number, and timers relating to refreshing the zone,
- MX : Mail eXchange. Points to a mail server,
- NS : Name Server (a DNS).

Output sections

HEADER	Displays the dig command version, the global options used, the type of operation (opcode), the status of the operation (NOERROR) and the message id (necessary to match responses to queries).
QUESTION	This is your input, the question that has been asked to the DNS.
ANSWER	The 2nd field is the time in seconds that the record may be cached (0 = don't cache), the 3rd field is the class (Internet (IN), Chaos (CH), Hesiod (HS)...), the 4th is the type (A, NS, CNAME, MX...) and the 5th, the IP.
AUTHORITY	This section contains the DNS name server that has the authority to answer your query (type: NS, Name Server).
ADDITIONAL	The additional section carries Resource Records related to the RRs from the other sections.
STATISTICS	Displays the time it took to get an answer, the IP of the DNS server used, the date and size of the message.

If you ever get confused about whether or not dig found any result for your query, check the ANSWER field from the header; if it's at 0, your query returned no proper answer.

Batch mode: multiple queries in one go

Using a list	`dig -f names.list`
Using several arguments	`dig centos.org MX +noall +answer suckless.org ANY +short`

Batch mode takes a filename as input; the file must be plain text and contain one domain per line:

$ cat names.list

redhat.com
ubuntu.com
perdu.com

Make that DNS talk !

Display only the ANSWER section	`dig opensuse.org +noall +answer`
Activate the short output	`dig perdu.com +short`
Reverse DNS (get name from IP)	`dig -x 208.97.177.124`
Use a specific DNS server	`dig @8.8.4.4 redhat.com`
Display the name resolution path	`dig google.com +trace`
Request a zone transfer	`dig microsoft.com AXFR`

A zone transfer is a mechanism allowing an administrator to replicate DNS databases across a set of DNS servers. There are two methods: full (aka AXFR) and incremental (aka IXFR). Zone transfers were often used by people wanting to retrieve a list of all the Resource Records of a DNS server. Nowadays, most servers will refuse your request, mostly for security reasons.

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