2 Domain Name Server Configuration Utilities -- NSC 3.1
4 (c) 1997--2008 Martin Mares <mj@ucw.cz>
6 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
9 ------------------------------------------------------------------------------------
10 WARNING: NSC has undergone significant changes between versions 2.3 and 2.99b.
11 See NEWS for the summary of changes. Most importantly, the configuration files are
12 NOT compatible with the old releases.
13 ------------------------------------------------------------------------------------
16 NSC is a set of shell and M4 scripts for easy maintenance of DNS zone files
17 and name server daemon configuration (currently available only for BIND 8.X,
18 but easily portable for other daemons). It has been designed to make administration
19 of a DNS server a piece of cake (unlike other utilities which resemble more
20 an English pudding :-) ), which includes automatic generation of reverse records
21 for all your hosts, handling of classless reverse delegations and support for IPv6
22 (AAAA and PTR in in6.arpa, not A6 and DNAME which seem to be dying out).
24 NSC requires GNU m4 and a POSIX-compatible shell, some of the extra utilities
25 require Perl 5. I've tested everything on Linux (Debian Woody), but the whole
26 package should run on other unices as well.
28 The whole package can be used and distributed according to the terms of the
29 GNU General Public License. See file COPYING in any of the GNU utility archives
30 (you should have one as you are expected to have at least GNU M4 ;-)).
33 0. Quick Howto for the Impatient
34 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
35 (everything will be explained in more detail in the subsequent sections)
37 - Create a directory where all NSC files will reside (e.g., /etc/named)
38 and copy everything from the NSC distribution here.
40 - Symlink /etc/bind/named.conf (or /etc/named.conf or where the config file
41 of your installation of BIND resides) to /etc/named/named.conf
43 - Change directory to /etc/named
45 - Edit cf/domains to suit your needs -- replace the example domains
48 - Create cf/<domain-name> for all domains (again, you can easily follow
51 - Run bin/nsconfig (Makefile and named.conf will be generated).
55 - Enjoy your new DNS setup. If everything goes OK, be happy. Else
56 write a bug report :-)
58 - Every time you modify the domain files
60 An interesting companion to this package is the DNS Sleuth -- a DNS zone
61 consistency checker. It's a simple utility written in Perl with help of the
62 DNS module and it should be able to detect all common errors in DNS setup
63 (I have written it after much disappointment with the other checkers).
64 The Sleuth is available online on http://atrey.karlin.mff.cuni.cz/~mj/sleuth/,
65 follow the links to download the source.
68 1. Directory structure
69 ~~~~~~~~~~~~~~~~~~~~~~
70 The NSC directory (/etc/named in the above example) contains the following
71 files and subdirectories:
73 cf/ - user-defined configuration files
74 cf/domains - the domain list (see Section 2)
75 cf/config - global settings (see Section 3)
76 cf/<domain> - each domain has its own config file
77 bin/ - commands (e.g., nsconfig)
78 m4/ - M4 scripts (used by the commands)
79 zone/ - primary zone files
80 bak/ - backups of zones we serve as a secondary NS for
81 ver/ - version files where NSC remembers version
82 numbers of the primary zones
84 How are different files created:
86 - You create everything in cf/.
87 - Then you run bin/nsconfig.
88 - Makefile and named.conf gets created according to cf/domains.
90 - The Makefile creates primary zone files in zone/ and version files
91 in ver/ and tells BIND to reload its configuration.
92 - BIND downloads contents of secondary zones and puts them to bak/.
95 2. The Domain List File
96 ~~~~~~~~~~~~~~~~~~~~~~~
97 The domain list contains configuration commands describing all domains handled
98 by your server and their parameters. In fact, it's a M4 script, but viewing it as
99 a config file is a good approximation (however, see Section 8 for some caveats).
100 Lines starting with a semicolon are treated as comments and ignored. Text outside
101 declarations is silently ignored.
105 PRIMARY(zone, [extra-files...])
106 Define a zone (domain) we run a primary name server for.
107 The contents of the zone are described in cf/<zone>
108 and possibly in other specified cf files (all files are
109 concatenated to produce a single configuration). See the next
110 section for a look inside these files.
112 When the zone name contains a slash (as happens in classless
113 reverse zones), it is replaced by "@" in the cf file name.
115 SECONDARY(zone, primary)
116 Define a zone we run a secondary name server for.
117 "primary" is an IP address of the primary name server.
119 REVERSE(network, primary-files...)
120 Define a reverse zone for the given network. The network name
121 consists of several numbers separated by dots, just like an IP
122 address does, but the network usually has only 3 components.
123 Each reverse zone has its own config file cf/<network> which
124 can of course specify the contents of the zone.
126 However, there is a more convenient method to generate the PTR
127 records directly from the A records: just specify the REVERSE
128 directive in cf/<network> and then include all the config files
129 for the primary zones containing hosts from this network. The
130 automatic concatenation of multiple primary-files comes very
133 In fact, REVERSE(network, p-f...) is almost an equivalent of
134 PRIMARY(REV(network), p-f...) where REV(network) is a macro
135 translating network numbers to names of the corresponding
136 reverse zones [e.g., REV(1.2.3) equals 3.2.1.in-addr.arpa].
137 The only difference is that although the domain name is translated
138 by REV, the config file is still named according to the network.
139 You can also use the REV macro explicitly, which can be handy
140 for example in SECONDARY declarations.
142 FORWARDED(zone, ip...)
143 Define a forwarding zone. All queries are forwarded to the
144 specified name servers.
147 Define an empty zone according to RFC 6303. This is usually done
148 for zones for which clients are known to erroneously ask queries
149 (e.g., reverse resolving of link-local addresses). The contents
150 served for these zones is taken from cf/blackhole.
152 ZONE_OPTIONS(`options;
155 Define options to be inserted to all subsequent zone declarations
156 until the next ZONE_OPTIONS command. Please keep in mind that the
157 semicolon character act as M4 comment, so you need to put the
158 closing quote at a separate line. See our example cf/domains.
161 Insert user data to named.conf, again beware of semicolons.
164 Insert user data to Makefile.
169 The domain files contain descriptions of all DNS records for the given
170 domain, starting with the SOA record. Again, these are M4 scripts and the
171 declarations are macro calls. Lines starting with a semicolon are treated
172 as comments and just copied to the generated zone file. Text outside
173 declarations is copied to the zone file as well, so you can spice up the NSC
174 output with your own records.
176 All host or domain names are either names relative to the current domain
177 with no dots inside or absolute names (in this case, NSC automatically
178 ensures that the trailing dot is present in the resource records). Relative
179 names with dots are not supported, but they are rare and you can always write
180 them as absolute anyway.
185 Generate a SOA record for the domain. This must be the first
186 declaration in the config file. The parameters of the SOA
187 are taken from configuration variables (see below). The
188 serial number is calculated from the version number remembered
189 in the version file, following the usual practice of encoding
190 current date and a sequence number within the current day
191 in the serial number, which is guaranteed to be strictly
192 increasing unless you perform more than 99 updates in a single
193 day (in which case NSC stops and tells you to tweak the serial
196 The SOA record otherwise acts like a sub-domain (D) declaration,
197 therefore it can be followed by other records like NS (mandatory)
201 Start declaration of a host. Doesn't generate anything, only
202 remembers the host's name.
205 Specify addresses for the current host. In the normal mode, it
206 creates A records, in the reverse mode, PTR records.
209 A shortcut for H(host) ADDR(addr...) -- in many cases everything
210 you need for a single host.
213 Like ADDR, but suppresses PTR records. (This one is useful if you
214 have a single IP address used for zillions of names and you want
215 to avoid having zillions of PTR records for the same address.)
218 A shortcut for H(host) DADDR(addr...)
221 Start declaration of a sub-domain. Technically the same as H(domain),
222 but this one should be more intuitive.
225 Specify a glue record for a name server contained within a sub-domain
226 it's a primary for. Currently it's an equivalent of DH(ns, addr...).
229 Specify a list of name server names for the current domain
230 (started by either a SOA or D declaration). Generates NS records.
233 Specify a list of mail exchangers for the current host or domain.
234 Each mail exchanger should be preceded by a priority. Generates
238 Specify a HINFO record for the current host. Very rare in the
242 Specify a list of aliases for the current host or domain.
243 Generates a series of CNAME records pointing from the aliases
244 to the current host/domain.
247 Specify a TXT record for the current host or domain.
250 Specify a RP (responsible person) record for the current host or domain.
251 The first argument is a mail address in DNS notation (with `@' replaced
252 by `.' as in the SOA record), the second one is a name of a TXT record
253 with contact information.
255 SRV(service, protocol, priority, weight, port, target)
256 Specify a SRV (service) record for the current host or domain.
259 Generate a CNAME record -- "src" points to "dest".
262 Generate a PTR record -- "src" points to "dest". It's a common
263 record in reverse zones (and although it's legal in forward
264 zones as well, such use is very rare), however it's more convenient
265 to have your PTR's generated by the REVERSE directive. But if you
266 need anything special, here is the tool.
268 REVBLOCK(subdomain, min, max)
269 Generate a series of CNAME records numbered from `min' to `max'
270 and pointing to the same name in the given sub-domain, finally
271 declaring the sub-domain as well, so you can continue with its
274 Example: REVBLOCK(a, 16, 18) NS(ns.xyzzy.org) yields
281 This is a very common construct for classless reverse delegations,
282 see Section 6 for more details.
285 Switch to reverse mode. From this point on, all output is suppressed
286 except for ADDR declarations belonging to the specified network which
287 are automatically converted to PTR records.
289 With help of this feature, defining reverse zones can be as easy as:
291 ; Reverse zone for 10.0.0.0/24 a.k.a. 0.0.10.in-addr.arpa.
293 NS(ns1.example.com, ns2.example.com)
295 ; Include all primary zones containing ADDR's from this range,
296 ; which can be accomplished by a multi-file REVERSE declaration
300 4. Configuration variables
301 ~~~~~~~~~~~~~~~~~~~~~~~~~~
302 There is a fair amount of configuration variables (which are in reality normal
303 M4 macros). Each variable has a hard-wired default value which can be overridden
304 in cf/config by re-defining the variable. Also, all other config files can specify
305 their local definitions, but you need to be careful to change the variable before
306 it is used for the first time.
308 To change the setting, use
310 define(`variable', `value')
312 As usually, even this config file is a M4 script. Comments can be started by
313 semicolons, text outside macros is ignored.
315 The following variables are available:
317 NAMED_RESTART_CMD Shell command for restarting the name server daemon
318 (default: ndc restart)
320 ROOT Root directory of the whole package (default: /etc/named)
321 CFDIR Directory with config files (default: cf)
322 ZONEDIR Directory with zone files (default: zone)
323 BAKDIR Directory with backup files (default: bak)
324 VERSDIR Directory with version files (default: var)
325 ROOTCACHE File with the cache of root name servers
327 REFRESH SOA record parameters
331 NSNAME Origin server (default: hostname of your machine)
332 MAINTNAME Domain maintainer name (default: root@NSNAME)
334 For the timing parameters, the following shortcuts are available:
336 HOURS(n) Convert hours to seconds
337 MINUTES(n) Convert minutes to seconds
338 DAYS(n) Convert days to seconds
343 The Makefile generated by NSC offers the following targets:
345 all (default) - update all zone files and reload the daemon
346 clean - clean all generated zone files and backups
347 clobber - clean + delete Makefile and named.conf
348 (wise to do after major reconfigurations)
349 distclean - clobber + delete all version files (use only
350 if you really know what you are doing as the
351 serial number information in newly generated
352 files might be inconsistent then).
355 6. Classless reverse delegations
356 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
357 NSC also supports classless delegations for reverse zones using the mechanism
358 described in RFC 2317, i.e. by putting CNAME records to the reverse zone which
359 point to records of the same name in a sub-domain which you can delegate directly.
361 For example if you want to delegate 64-127 in 0.0.10.in-addr.arpa to ns.example.net,
362 you create a 64/26 sub-domain (26 is the network prefix length) and add the following
363 records to 0.0.10.in-addr.arpa:
365 64 CNAME 64.64/26.0.0.10.in-addr.arpa.
366 65 CNAME 65.64/26.0.0.10.in-addr.arpa.
368 127 CNAME 127.64/26.0.0.10.in-addr.arpa.
370 64/26 NS ns.example.net.
372 Then you configure ns.example.net to be a primary name server for the zone
373 64/26.0.0.10.in-addr.arpa and put the PTR records there:
375 64 PTR sixty-four.example.net.
376 65 PTR sixty-five.example.net.
378 127 PTR two-to-seven-minus-one.example.net.
380 NSC offers special primitives for configuring such delegations, but not limited
381 to the sub-domain name syntax shown above (which is recommended by the RFC, but it's
382 far from being the only one used in the real world, other possibilities being for
383 example 64-127, 64+64 etc.).
385 The CNAME block can be generated by the REVBLOCK(subdomain-name, low-addr, high-addr)
386 directive in the configuration of the whole reverse zone. The example above would
389 REVBLOCK(64/26, 64, 127)
391 The sub-zone can be created automatically like any another reverse zone, you only
392 need to use the three-parameter form of the REVERSE directive to specify the
393 address range in order to filter out possible hosts falling outside your range.
395 CAVEAT: The slashes in zone names are automatically translated to @'s when forming
398 Again for the example above, you need to put the following to cf/domains:
400 REVERSE(10.0.0.64/26, <list-of-domains-to-gather-the-addresses-from>)
402 And to cf/64@26.0.0.10:
404 SOA(REV(10.0.0.64/26))
405 NS(<list-of-name-servers>)
406 REVERSE(10.0.0, 64, 127)
408 NOTE: It's usually helpful to configure the primary name server for the parent
409 domain (i.e., the one where you configure the delegation and create the CNAME's)
410 as a secondary for the sub-zone as well, so if it replies with the CNAME, it will
411 include the PTR record pointed to by the CNAME in the additional section of its
412 reply, eliminating the need for an extra query.
417 NSC also supports IPv6 in a pretty straightforward form: wherever you can write
418 an IPv4 address, you can use an IPv6 address as well. Incomplete IP addresses
419 or ranges used for specifying address blocks for reverse delegations are replaced
420 by network prefixes of the standard form <address>/<prefix-length>.
424 H(ianus, 1.2.3.4, fec0::1234:5678:9abc:def0)
426 specifies a dual-stack host with both an A record and an AAAA record.
428 CAVEAT: The backward-compatible IPv6 address syntax with ":v.w.x.y" at the end
429 is not supported. All other syntaxes and quirks hopefully are.
432 8. Interaction with M4
433 ~~~~~~~~~~~~~~~~~~~~~~
434 All config files are fully-fledged M4 scripts, so you can use any M4 features
435 you need, the most helpful one being definition of your own macros by
437 define(`macro_name', `expansion')
439 However, there is a couple of things you need to care about:
441 o The comment character is redefined to `;'. I.e., wherever a semicolon
442 occurs, the rest of the line is a comment which is copied verbatim
443 to the output file (if the output is not suppressed like in case
444 of the cf/domains file).
446 o Names starting with 'nsc_' or spelled in all caps are reserved
447 for the NSC itself and unless documented, messing with them can
448 bring surprising results. If you need to use such a name in your
449 zone file (maybe you like to shout in your host names :-) ),
450 quote it with ` and '.
452 o Don't use commas, quotes nor parentheses in your record names.
457 convert A simple Perl script for conversion of zone files to NSC
458 domain files. Requires the Net::DNS module (available from
459 CPAN at ftp.cpan.org; present in recent versions of Perl).
460 Keep in mind that the script is very simple and its craft
461 is of a very limited kind, so check its output carefully.
463 chkdel A simple Perl script for checking of domain delegations --
464 it checks all PRIMARY and SECONDARY records in cf/domains
465 against NS records. Requires the Net::DNS module and also
466 some tweaking of parameters at the top of the script.