Name

tinydns-data — compile the database used by tinydns

Synopsis

tinydns-data

Description

tinydns-data compiles a database in source form, in the file data, into a compiled form, in the file data.cdb, that is used by tinydns(1). The compiled database in data.cdb is a Bernstein Constant Database file.

tinydns-data updates data.cdb atomically, building a replacement in data.cdb.tmp and atomically renaming that replacement into place when it has completely and successfully built it it and written it to disc. So you can use it safely while tinydns(1) is running.

Data format

The DNS information in data is a series of lines. It is very easy for programs to edit; and can be mainpulated with with UNIX tools such as awk(1) and sed(1). There are several types of lines, as shown below.

Each line starts with a special character and continues with a series of colon-separated fields. In some cases the fields may be omitted; however, all colons must be included except at the end of the line. Spaces and tabs at the end of a line are ignored. Blank lines are ignored.

IP addresses

Many lines contain an ip field that is an IP address.

IPv4 addresses are written in the conventional human-readable form: 192.0.2.234, 10.20.40.80

IPv6 addresses are written in the conventional human-readable form, except that (since they are field separator characters here) colons are changed to underscores and the double-colon convention is not used. All addresses must have all 8 groups: 2001_bd8_3_4_5_6_7_8, fd57_8012_f61c_0_20a2_9013_7ec4_7ab3

Timestamps and scheduled changes

Each line contains a ttl ("time to live") specifying the number of seconds that the line's DNS records may be cached. Beware that cache times below 300 seconds will be treated as 300 by some clients, and NS cache times below 2 seconds can cause lookup failures. You may omit ttl; tinydns-data will use default cache times, carefully selected to work well in normal situations.

You may include a timestamp on each line. If ttl is nonzero (or omitted), the timestamp is a starting time for the information in the line; the line will be ignored before that time. If ttl is zero, the timestamp is an ending time ("time to die") for the information in the line; tinydns dynamically adjusts ttl so that the line's DNS records are not cached for more than a few seconds past the ending time. A timestamp is an external TAI64 timestamp, printed as 16 lowercase hexadecimal characters. For example, the lines

+www.heaven.af.mil:192.0.2.234:0:4000000038af1379
+www.heaven.af.mil:192.0.2.235::4000000038af1379

specify that www.heaven.af.mil will have address 192.0.2.234 until time 4000000038af1379 (2000-02-19 22:04:31 UTC) and will then switch to IP address 192.0.2.235.

Client locations

You may include a client location lo on each line. The line is ignored for clients outside that location. Client locations are specified by % lines:

 %lo:ipprefix

means that IP addresses starting with ipprefix are in location lo. lo is a sequence of one or two ASCII letters. A client is in only one location; longer prefixes override shorter prefixes. For example,

%in:192.168
%ex
+jupiter.heaven.af.mil:192.168.1.2:::in
+jupiter.heaven.af.mil:192.0.2.234:::ex

specifies that jupiter.heaven.af.mil has address 192.168.1.2 for clients in the 192.168.* network and address 192.0.2.234 for everyone else.

Line types

#comment

Comment line. The line is ignored.

.fqdn:ip:x:ttl:timestamp:lo

Apex name server for domain fqdn. tinydns-data creates

  • an NS ("name server") record showing x.ns.fqdn as a name server for fqdn;

  • an A ("address") record showing ip as the IP address of x.ns.fqdn; and

  • an SOA ("start of authority") record for fqdn listing x.ns.fqdn as the primary name server and hostmaster@fqdn as the contact address.

You may have several name servers for one domain, with a different x for each server.

If x contains a dot then tinydns-data will use x as the server name rather than x.ns.fqdn. This feature is provided only for compatibility reasons; names not ending with fqdn will force clients to contact parent servers much more often than they otherwise would, and will reduce the overall reliability of DNS. You should omit ip if x has IP addresses assigned elsewhere in the data file; in this case, tinydns-data will omit the A record.

Examples:

.panic.mil:1.8.7.55:a

creates an NS record showing a.ns.panic.mil as a name server for panic.mil, an A record showing 1.8.7.55 as the IP address of a.ns.panic.mil, and an SOA record for panic.mil.

.panic.mil:1.8.7.56:dns2.panic.mil

creates an NS record showing dns2.panic.mil as a name server for panic.mil, an A record showing 1.8.7.56 as the IP address of dns2.panic.mil, and an SOA record for panic.mil.

.panic.mil::a.ns.heaven.af.mil

creates an NS record showing a.ns.heaven.af.mil as a name server for panic.mil, and an SOA record for panic.mil.

&fqdn:ip:x:ttl:timestamp:lo

Delegation to name server for domain fqdn. tinydns-data creates

  • an NS record showing x.ns.fqdn as a name server for fqdn and

  • an A record showing ip as the IP address of x.ns.fqdn.

Normally & is used for domains delegated by this server to child servers, while . is used for domains delegated to this server.

You may have several name servers for one domain, with a different x for each server. If x contains a dot then it is treated specially; as for . lines.

Examples:

&serious.panic.mil:1.8.248.6:a

creates an NS record showing a.ns.serious.panic.mil as a name server for serious.panic.mil, and an A record showing 1.8.248.6 as the IP address of a.ns.serious.panic.mil.

&serious.panic.mil:1.8.248.7:ns7.panic.mil

creates an NS record showing ns7.panic.mil as a name server for serious.panic.mil, and an A record showing 1.8.248.7 as the IP address of ns7.panic.mil.

=fqdn:ip:ttl:timestamp:lo

Host fqdn with IP address ip. tinydns-data creates

  • an A record showing ip as the IP address of fqdn and

  • a PTR ("pointer") record showing fqdn as the name of d.c.b.a.in-addr.arpa if ip is a.b.c.d.

Remember to specify name servers for some suffix of fqdn; otherwise tinydns will not respond to queries about fqdn. The same comment applies to other records described below. Similarly, remember to specify name servers for some suffix of d.c.b.a.in-addr.arpa, if that domain has been delegated to you.

Example:

=button.panic.mil:1.8.7.108

creates an A record showing 1.8.7.108 as the IP address of button.panic.mil, and a PTR record showing button.panic.mil as the name of 108.7.8.1.in-addr.arpa.

+fqdn:ip:ttl:timestamp:lo

Server side alias fqdn with IP address ip. This is just like =fqdn:ip:ttl except that tinydns-data does not create the PTR record.

Example:

+button.panic.mil:1.8.7.109

creates an A record showing 1.8.7.109 as another IP address for button.panic.mil.

-fqdn:ip:ttl:timestamp:lo

This type of line is used by programs that automatically edit + lines in data to temporarily exclude addresses of overloaded or dead machines. The line is ignored.

Sfqdn:ip:x:p:prio:wt:ttl:timestamp:lo

Service for fqdn. tinydns-data creates

  • a SRV ("service") record showing x.srv.fqdn as a service for fqdn on port p with priority prio and weight wt, and

  • an A record showing ip as the IP address of x.srv.fqdn.

You may omit prio and wt; the defaults are 0. If x contains a dot then it is treated specially; see above. You may create several SRV records for fqdn, with a different x for each server.

Example:

S_sip._udp.panic.mil:1.8.7.88:sip.panic.mil:5060:10:20

creates a SRV record showing port 5060 of sip.panic.mil as a SIP/UDP service for panic.mil with priority 10 and wt 20, and an A record showing 1.8.7.88 as the IP address of sip.panic.mil.

@fqdn:ip:x:dist:ttl:timestamp:lo

Mail exchanger for fqdn. tinydns-data creates

  • an MX ("mail exchanger") record showing x.mx.fqdn as a mail exchanger for fqdn at distance dist and

  • an A record showing ip as the IP address of x.mx.fqdn.

You may omit dist; the default distance is 0. If x contains a dot then it is treated specially; see above. You may create several MX records for fqdn, with a different x for each server. Make sure to arrange for the SMTP server on each IP address to accept mail for fqdn.

Example:

@panic.mil:1.8.7.88:mail.panic.mil

creates an MX record showing mail.panic.mil as a mail exchanger for panic.mil at distance 0, and an A record showing 1.8.7.88 as the IP address of mail.panic.mil.

'fqdn:s:ttl:timestamp:lo

TXT ("text") record for fqdn. tinydns-data creates

  • a TXT record for fqdn containing the string s.

You may use octal \nnn codes to include arbitrary bytes inside s; for example, \072 is a colon.

^fqdn:p:ttl:timestamp:lo

PTR record for fqdn. tinydns-data creates

  • a PTR record for fqdn pointing to the domain name p.

Usually a = line is a more convenient way to create a mapping from an IP address to a domain name.

Cfqdn:p:ttl:timestamp:lo

Client side alias fqdn with target p. tinydns-data creates

  • a CNAME record for fqdn pointing to the domain name p.

Don't use Cfqdn if there are any other records for fqdn. Don't use Cfqdn for common aliases; use +fqdn instead. Remember the wise words of Inigo Montoya: "You keep using CNAME records. I do not think they mean what you think they mean."

Zfqdn:mname:rname:ser:ref:ret:exp:min:ttl:timestamp:lo

SOA record for fqdn showing mname as the primary name server, rname (with the first . converted to @) as the contact address, ser as the serial number, ref as the refresh time, ret as the retry time, exp as the expire time, and min as the minimum time.

ser, ref, ret, exp, and min may be omitted; they default to, respectively, the modification time of the data file, 16384 seconds, 2048 seconds, 1048576 seconds, and 2560 seconds.

Usually a . line is a more convenient way to create SOA records.

:fqdn:n:rdata:ttl:timestamp:lo

Generic record for fqdn. tinydns-data creates

  • a record of type n for fqdn showing rdata.

n must be an integer between 1 and 65535; it must not be 2 (NS), 5 (CNAME), 6 (SOA), 12 (PTR), 15 (MX), or 252 (AXFR). The proper format of rdata depends on n. You may use octal \nnn codes to include arbitrary bytes inside rdata.

Example

A typical data file:

=lion.heaven.af.mil:1.2.3.4
@heaven.af.mil:1.2.3.4
@3.2.1.in-addr.arpa:1.2.3.4

=tiger.heaven.af.mil:1.2.3.5
.heaven.af.mil:1.2.3.5:a
.3.2.1.in-addr.arpa:1.2.3.5:a

=bear.heaven.af.mil:1.2.3.6
.heaven.af.mil:1.2.3.6:b
.3.2.1.in-addr.arpa:1.2.3.6:b

=cheetah.heaven.af.mil:1.2.3.248
=panther.heaven.af.mil:1.2.3.249 

History

tinydns-data was originally part of Daniel J. Bernstein's djbdns toolset in 2000.

Author

Original code and documentation by Daniel J. Bernstein. Documentation modernizations by Jonathan de Boyne Pollard.