Syntaxdig [@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...] |
ConfigTired of always typing the same options ? Create a Run Control file for dig. | vi $HOME/.digrc
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$ 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
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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 sectionsHEADER | 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 goUsing a list | dig -f names.list
| Using several arguments | dig centos.org MX +noall +answer suckless.org ANY +short
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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
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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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