In the previous section we used the tinydns add-* utilities to make some initial entries into a tinydns database:
# cd /service/tinydns/root # ./add-ns example.org 126.96.36.199 # ./add-host alice.example.org 188.8.131.52 # ./add-host betty.example.org 184.108.40.206 # ./add-host carol.example.org 220.127.116.11 # ./add-mx example.org 18.104.22.168 # ./add-alias www.example.org 22.214.171.124 # make
This command sequence configures tinydns entries for a network with three hosts:
The add-* utilities simply append each entry to a plain-text file named /service/tinydns/root/data. The make command then converts the plain-text data to a fast-hashing cdb file named data.cdb.
Now we are interested in looking into the plain-text file, data. This is what we will see after the original add-* entries shown above:
# cat data .example.org:126.96.36.199:a:259200 =alice.example.org:188.8.131.52:86400 =betty.example.org:184.108.40.206:86400 =carol.example.org:220.127.116.11:86400 @example.org:18.104.22.168:a::86400 +www.example.org:22.214.171.124:86400
In other words, each ./add-* command puts a corresponding line into the data file:
|./add-* utility...||...data line|
|./add-ns example.org 126.96.36.199||.example.org:188.8.131.52:a:259200|
|./add-host alice.example.org 184.108.40.206||=alice.example.org:220.127.116.11:86400|
|./add-host betty.example.org 18.104.22.168||=betty.example.org:22.214.171.124:86400|
|./add-host carol.example.org 126.96.36.199||=carol.example.org:188.8.131.52:86400|
|./add-mx example.org email@example.com:184.108.40.206:a::86400|
|./add-alias www.example.org 220.127.116.11||+www.example.org:18.104.22.168:86400|
The data file consists of a set of heterogeneous record types, with one record per line. Each record type is indicated by the first character of the record. The data file shown here has 4 types of records:
The actual data for each record follows the record-type character, and consists of a set of colon-delimited (':') fields. Each record type is defined with its own set of fields. That is, while field definitions are similar among different types of records, the order and type of fields in a record are specific to that record type.
In practice, the add-* utilities are useful only to create an initial set of template entries into the data file. After that, for any maintenance beyond the initial setup, it is easier to work with the data file directly, using the yank/paste features of a text editor to quickly make additional entries as required.
Notice also that there are no corresponding del-* or mod-* utilities provided, to delete or modify tinydns record entries. And some record types are not supplied with add-* utilities at all, including text, cname, and generic records. Again, for this kind of maintenance and modification, you simply edit the plain-text data file directly.
So where can you find the definitions for all the specific tinydns record types? There is no better place than from djb himself: http://cr.yp.to/djbdns/tinydns-data.html. Here's a summary of the most common for quick reference:
|prefix||description||field specs||DNS records created||./add-* util|
|.||nameserver||.domain:ip:xname:ttl:tai64:loc||NS, A, SOA||./add-ns domain ip|
|=||hostname||=hostname:ip:ttl:tai64:loc||A, PTR||./add-host hostname ip|
|+||alias||+hostname:ip:ttl:tai64:loc||A||./add-alias hostname ip|
|@||mail exchanger||@domain:ip:xname:distance:ttl:tai64:loc||MX, A||./add-mx domain ip|
both domain and hostname should be fully qualified
ip should be a "dot-quad" (IPv4) IP address
ttl indicates "time to live" in seconds (86400 = 1 day)
tai64 is an optional timestamp used to control record activation/expiration; see the tinydns-data page for more information
the xname in some record types is used to extend the base domain name to create a specific A record hostname; see the tinydns-data page for more information
loc is an optional location specifier, and with corresponding location records may be used to setup "split-view" DNS; see the appendix of http://www.guinix.com/technote/dualdns.html for more information
comment lines can be added as necessary to provide internal documentation and improve readability
Note also that tinydns is pretty smart, and will generate more than one DNS resource record when appropriate. For example, a tinydns '=' record will generate both A and PTR resource records automatically. Here is a quick reference to some of the most common DNS resource record types:
|A||1||"address"||hostname --> address|
|NS||2||"nameserver"||nameserver for domain|
|CNAME||5||"canonical name"||use A records instead!|
|SOA||6||"start of authority"||authority for domain|
|PTR||12||"pointer"||address --> hostname|
|MX||15||"mail exchanger"||SMTP host for domain|
|TXT||16||"text"||hostname --> anystring|
The numerical codes shown in this table are the numbers seen in response to queries with dnsq. For example, in the query:
$ dnsq mx example.org 22.214.171.124 15 example.org: 101 bytes, 1+1+1+2 records, response, authoritative, noerror query: 15 example.org answer: example.org 86400 MX 0 a.mx.example.org authority: example.org 259200 NS a.ns.example.org additional: a.mx.example.org 86400 A 126.96.36.199 additional: a.ns.example.org 259200 A 188.8.131.52
The '15' displayed in response lines refers to the MX record type. (Resource records and type codes are defined by the RFCs covering DNS, in this case RFC 1035.)
A few other comments:
If managing a large domain, and/or several domains, a central SQL database can be used to facilitate the coordination of DNS and DHCP configuration. For tinydns, just automate the procedure:
SQL--> data--> data.cdb
Another way to handle multiple domains is to create separate data files for each domain --eg., data-example.org, data-example.edu, etc,-- then cat them all together before running make.
If you are interested in publishing MX records for a qmail-qmtpd service, see our qmtp page for information on how to use the "distance" field to support MXPS, the "Mail Exchange Protocol Switch".
One last reminder: don't forget to run make after editing data! The changes will be immediately available; no need to restart the tinydns service.
Copyright © 2002, 2003, 2004, Wayne Marshall.
All rights reserved.
Last edit 2004.06.01, wcm.