The tinydns-data format

The helper applications modify the data file, a text file that uses the tinydns-data format. This format is simple, compact, and easy to modify. Here are the lines created by the helper-application examples in the previous section: .hackenbush.com:192.193.194.195:a:259200 &hackenbush.com:200.201.202.203:a:259200 =hugo.hackenbush.com:192.193.194.200:86400 +another.hackenbush.com:192.193.194.200:86400 @mail.hackenbush.com:192.193.194.201:a::86400

Rather than using the helper applications, we could have created the lines with a text editor and used the default ttl values: .hackenbush.com:192.193.194.195:a &hackenbush.com:200.201.202.203:a =hugo.hackenbush.com:192.193.194.200 +another.hackenbush.com:192.193.194.200 @mail.hackenbush.com:192.193.194.201:a

If the primary name server was within our domain (at a.ns.hackenbush.com) but a secondary name server was at ns.flywheel.com, here’s how to specify it:

.hackenbush.com:192.193.194.195:a &hackenbush.com::ns.flywheel.com

If the primary name server was at ns.flywheel.com, here’s how to specify that: .hackenbush.com::ns.flywheel.com

A few characters perform a lot of work and avoid some common sources of error in BIND zone files: • Records starting with a dot (.) create an SOA record, an NS record, and an A record if an IP

address was specified.

• Records starting with an equals sign (=) create A and PTR records. 6.5.5.3 tinydns data reference

Each record (line) in a tinydns-data (formatted) file starts with an identifying character. Fields are separated by colons. Trailing fields and their colons may be omitted, and their default values will be used. Table 6-4 describes some fields common to many types of tinydns-data records.

Table 6-4. Common tinydns-data fields

Field Description Default

dom A domain name like hackenbush.com. None.

fqdn A fully qualified domain name like be used: *.fqdn means every name ending with .fqdn, unless a name has a hugo.hackenbush.com. A wild card can also

more specific record. None.

ip An IP address like 192.193.194.195. None.

ttl Time-to-live (number of seconds that the record’s data can be cached).

SOA: 2560 (42.6 minutes) NS: 259200 (3 days) MX, A, others: 86400 (1 day). ts

If ttl is missing or nonzero, the starting time for information in this line; if is zero, the end time. ts is specified as an external TAI64 timestamp, which is a 16-character, lowercase hex string with a resolution of one second. The hex value 4000000000000000 corresponds to ISO time 1970-01-01 00:00:00, the reference start time for Unix systems.

Empty, meaning the line is active. loc A location-identifier string, used to provide different answers to clients, _{depending on their locations; see the djbdns documentation for details.} None.

The next table, Table 6-5, shows the correspondence between djbdns helper applications and equivalent lines in data; you can specify your data either way. Notice that the helper applications require IP addresses rather than names; if you wish to specify a name instead, you need to edit the data file.

Table 6-5. Helper-application syntax versus tinydns-data syntax

Helper application

syntax Data format Description

add-ns

dom ip .dom:ip:x:ttl:ts:loc

Specify a primary name server for domain dom. Create an SOA record for the domain and an NS record for the name server specified as x and/or ip. If x contains any dots, it is treated as a literal hostname; otherwise, it is interpreted as x.ns.dom. If ip is present, an A record is created.

Using add-ns generates the sequential values a, b, etc. for x. These correspond to a.ns.dom, b.ns.dom, etc. This default behavior generates in-bailiwick (intradomain) names for the name servers. Specifying a domain’s name server within the domain itself avoids a trip to the root name servers for resolution.

Add- childns

dom ip &dom:ip:x:ttl:ts:loc

Specify a domain’s secondary name server. Create only an NS record for the name server, specified as x and/or ip. If x contains any dots, it is treated as a literal hostname; otherwise, it is interpreted as x.ns.dom. If ip is present, an A record is

created.

Add-childns also generates a, b, etc. for x. Add-host

fqdn ip =fqdn:ip:ttl:ts

Specify a host: create an A record (fqdn

[Symbol_MonotypeSorts_217] ip) and a PTR record (reverse-ip.in-addr.arpa

[Symbol_MonotypeSorts_217] fqdn). Add-

alias

fqdn ip +fqdn:ip:ttl:ts

Specify an alias: create another A record (fqdn [Symbol_MonotypeSorts_217] ip).

Add-mx

fqdn ip @dom:ip:x:dist:ttl:ts

Specify a mail server: create an MX record. If x contains any dots, it is treated as a literal hostname; otherwise, it is interpreted as x.mx.dom. dist in distance and defaults to 0.

Add-mx also generates sequential hostnames of a, b, etc. for x. The less common record types shown in Table 6-6 have no helper applications.

Table 6-6. Less-common record types

Helper application

syntax Data format Description

(No helper) Zdom:fqdn:con:ser:ref:ret:exp:min:ttl:ts:loc

Create only an SOA record for dom, with contact con, serial number ser, refresh time ref, retry time ret, expire time exp, and minimum time min. (No helper) Chost2:fqdn:ttl:ts:loc Create a CNAME record for _{host2 to refer to host.}

(No helper) ’fqdn:text:ttl:ts:loc

Create a TXT record for fqdn. text can contain octal escape codes (e.g., \F3D) to create non- ASCII values.

(No helper) ^fqdn:ip:ttl:ts:loc Create a PTR record for fqdn [Symbol_MonotypeSorts_217] ip.

(No helper) :fqdn:type:data:ttl:ts:loc

Create a record of type type (an integer between 1 and 65,535). Data bytes data may contain octal escapes.

After making changes to a datafile, type make. This runs the tinydns-data program to convert data to data.cdb. The conversion will only overwrite the existing database if the source data is consistent. tinydns will start serving the new data immediately.