2 Domain Name Server Configuration Utilities -- NSC 3.0.2
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 SECONDARY(zone, primary)
113 Define a zone we run a secondary name server for.
114 "primary" is an IP address of the primary name server.
116 REVERSE(network, primary-files...)
117 Define a reverse zone for the given network. The network name
118 consists of several numbers separated by dots, just like an IP
119 address does, but the network usually has only 3 components.
120 Each reverse zone has its own config file cf/<network> which
121 can of course specify the contents of the zone.
123 However, there is a more convenient method to generate the PTR
124 records directly from the A records: just specify the REVERSE
125 directive in cf/<network> and then include all the config files
126 for the primary zones containing hosts from this network. The
127 automatic concatenation of multiple primary-files comes very
130 In fact, REVERSE(network, p-f...) is almost an equivalent of
131 PRIMARY(REV(network), p-f...) where REV(network) is a macro
132 translating network numbers to names of the corresponding
133 reverse zones [e.g., REV(1.2.3) equals 3.2.1.in-addr.arpa].
134 The only difference is that although the domain name is translated
135 by REV, the config file is still named according to the network.
136 You can also use the REV macro explicitly, which can be handy
137 for example in SECONDARY declarations.
139 ZONE_OPTIONS(`options;
142 Define options to be inserted to all subsequent zone declarations
143 until the next ZONE_OPTIONS command. Please keep in mind that the
144 semicolon character act as M4 comment, so you need to put the
145 closing quote at a separate line. See our example cf/domains.
148 Insert user data to named.conf, again beware of semicolons.
151 Insert user data to Makefile.
156 The domain files contain descriptions of all DNS records for the given
157 domain, starting with the SOA record. Again, these are M4 scripts and the
158 declarations are macro calls. Lines starting with a semicolon are treated
159 as comments and just copied to the generated zone file. Text outside
160 declarations is copied to the zone file as well, so you can spice up the NSC
161 output with your own records.
163 All host or domain names are either names relative to the current domain
164 with no dots inside or absolute names (in this case, NSC automatically
165 ensures that the trailing dot is present in the resource records). Relative
166 names with dots are not supported, but they are rare and you can always write
167 them as absolute anyway.
172 Generate a SOA record for the domain. This must be the first
173 declaration in the config file. The parameters of the SOA
174 are taken from configuration variables (see below). The
175 serial number is calculated from the version number remembered
176 in the version file, following the usual practice of encoding
177 current date and a sequence number within the current day
178 in the serial number, which is guaranteed to be strictly
179 increasing unless you perform more than 99 updates in a single
180 day (in which case NSC stops and tells you to tweak the serial
183 The SOA record otherwise acts like a sub-domain (D) declaration,
184 therefore it can be followed by other records like NS (mandatory)
188 Start declaration of a host. Doesn't generate anything, only
189 remembers the host's name.
192 Specify addresses for the current host. In the normal mode, it
193 creates A records, in the reverse mode, PTR records.
196 A shortcut for H(host) ADDR(addr...) -- in many cases everything
197 you need for a single host.
200 Like ADDR, but suppresses PTR records. (This one is useful if you
201 have a single IP address used for zillions of names and you want
202 to avoid having zillions of PTR records for the same address.)
205 A shortcut for H(host) DADDR(addr...)
208 Start declaration of a sub-domain. Technically the same as H(domain),
209 but this one should be more intuitive.
212 Specify a glue record for a name server contained within a sub-domain
213 it's a primary for. Currently it's an equivalent of DH(ns, addr...).
216 Specify a list of name server names for the current domain
217 (started by either a SOA or D declaration). Generates NS records.
220 Specify a list of mail exchangers for the current host or domain.
221 Each mail exchanger should be preceded by a priority. Generates
225 Specify a HINFO record for the current host. Very rare in the
229 Specify a list of aliases for the current host or domain.
230 Generates a series of CNAME records pointing from the aliases
231 to the current host/domain.
234 Specify a TXT record for the current host or domain.
237 Specify a RP (responsible person) record for the current host or domain.
238 The first argument is a mail address in DNS notation (with `@' replaced
239 by `.' as in the SOA record), the second one is a name of a TXT record
240 with contact information.
242 SRV(service, protocol, priority, weight, port, target)
243 Specify a SRV (service) record for the current host or domain.
246 Generate a CNAME record -- "src" points to "dest".
249 Generate a PTR record -- "src" points to "dest". It's a common
250 record in reverse zones (and although it's legal in forward
251 zones as well, such use is very rare), however it's more convenient
252 to have your PTR's generated by the REVERSE directive. But if you
253 need anything special, here is the tool.
255 REVBLOCK(subdomain, min, max)
256 Generate a series of CNAME records numbered from `min' to `max'
257 and pointing to the same name in the given sub-domain, finally
258 declaring the sub-domain as well, so you can continue with its
261 Example: REVBLOCK(a, 16, 18) NS(ns.xyzzy.org) yields
268 This is a very common construct for classless reverse delegations,
269 see Section 6 for more details.
272 Switch to reverse mode. From this point on, all output is suppressed
273 except for ADDR declarations belonging to the specified network which
274 are automatically converted to PTR records.
276 With help of this feature, defining reverse zones can be as easy as:
278 ; Reverse zone for 10.0.0.0/24 a.k.a. 0.0.10.in-addr.arpa.
280 NS(ns1.example.com, ns2.example.com)
282 ; Include all primary zones containing ADDR's from this range,
283 ; which can be accomplished by a multi-file REVERSE declaration
287 4. Configuration variables
288 ~~~~~~~~~~~~~~~~~~~~~~~~~~
289 There is a fair amount of configuration variables (which are in reality normal
290 M4 macros). Each variable has a hard-wired default value which can be overridden
291 in cf/config by re-defining the variable. Also, all other config files can specify
292 their local definitions, but you need to be careful to change the variable before
293 it is used for the first time.
295 To change the setting, use
297 define(`variable', `value')
299 As usually, even this config file is a M4 script. Comments can be started by
300 semicolons, text outside macros is ignored.
302 The following variables are available:
304 NAMED_RESTART_CMD Shell command for restarting the name server daemon
305 (default: ndc restart)
307 ROOT Root directory of the whole package (default: /etc/named)
308 CFDIR Directory with config files (default: cf)
309 ZONEDIR Directory with zone files (default: zone)
310 BAKDIR Directory with backup files (default: bak)
311 VERSDIR Directory with version files (default: var)
312 ROOTCACHE File with the cache of root name servers
314 REFRESH SOA record parameters
318 NSNAME Origin server (default: hostname of your machine)
319 MAINTNAME Domain maintainer name (default: root@NSNAME)
321 BIND_OPTIONS Extra options to put to the options { ... } section of named.conf
323 For the timing parameters, the following shortcuts are available:
325 HOURS(n) Convert hours to seconds
326 MINUTES(n) Convert minutes to seconds
327 DAYS(n) Convert days to seconds
329 For the BIND_OPTIONS, we offer:
331 FORWARD(ip...) Try to ask the given name servers first to see if they
332 have the reply cached.
333 SLAVE(ip...) Pass all non-local requests to the given name servers.
338 The Makefile generated by NSC offers the following targets:
340 all (default) - update all zone files and reload the daemon
341 clean - clean all generated zone files and backups
342 clobber - clean + delete Makefile and named.conf
343 (wise to do after major reconfigurations)
344 distclean - clobber + delete all version files (use only
345 if you really know what you are doing as the
346 serial number information in newly generated
347 files might be inconsistent then).
350 6. Classless reverse delegations
351 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
352 NSC also supports classless delegations for reverse zones using the mechanism
353 described in RFC 2317, i.e. by putting CNAME records to the reverse zone which
354 point to records of the same name in a sub-domain which you can delegate directly.
356 For example if you want to delegate 64-127 in 0.0.10.in-addr.arpa to ns.example.net,
357 you create a 64/26 sub-domain (26 is the network prefix length) and add the following
358 records to 0.0.10.in-addr.arpa:
360 64 CNAME 64.64/26.0.0.10.in-addr.arpa.
361 65 CNAME 65.64/26.0.0.10.in-addr.arpa.
363 127 CNAME 127.64/26.0.0.10.in-addr.arpa.
365 64/26 NS ns.example.net.
367 Then you configure ns.example.net to be a primary name server for the zone
368 64/26.0.0.10.in-addr.arpa and put the PTR records there:
370 64 PTR sixty-four.example.net.
371 65 PTR sixty-five.example.net.
373 127 PTR two-to-seven-minus-one.example.net.
375 NSC offers special primitives for configuring such delegations, but not limited
376 to the sub-domain name syntax shown above (which is recommended by the RFC, but it's
377 far from being the only one used in the real world, other possibilities being for
378 example 64-127, 64+64 etc.).
380 The CNAME block can be generated by the REVBLOCK(subdomain-name, low-addr, high-addr)
381 directive in the configuration of the whole reverse zone. The example above would
384 REVBLOCK(64/26, 64, 127)
386 The sub-zone can be created automatically like any another reverse zone, you only
387 need to use the three-parameter form of the REVERSE directive to specify the
388 address range in order to filter out possible hosts falling outside your range.
390 CAVEAT: The slashes in zone names are automatically translated to @'s when forming
393 Again for the example above, you need to put the following to cf/domains:
395 REVERSE(10.0.0.64/26, <list-of-domains-to-gather-the-addresses-from>)
397 And to cf/64@26.0.0.10:
399 SOA(REV(10.0.0.64/26))
400 NS(<list-of-name-servers>)
401 REVERSE(10.0.0, 64, 127)
403 NOTE: It's usually helpful to configure the primary name server for the parent
404 domain (i.e., the one where you configure the delegation and create the CNAME's)
405 as a secondary for the sub-zone as well, so if it replies with the CNAME, it will
406 include the PTR record pointed to by the CNAME in the additional section of its
407 reply, eliminating the need for an extra query.
412 NSC also supports IPv6 in a pretty straightforward form: wherever you can write
413 an IPv4 address, you can use an IPv6 address as well. Incomplete IP addresses
414 or ranges used for specifying address blocks for reverse delegations are replaced
415 by network prefixes of the standard form <address>/<prefix-length>.
419 H(ianus, 1.2.3.4, fec0::1234:5678:9abc:def0)
421 specifies a dual-stack host with both an A record and an AAAA record.
423 CAVEAT: The backward-compatible IPv6 address syntax with ":v.w.x.y" at the end
424 is not supported. All other syntaxes and quirks hopefully are.
427 8. Interaction with M4
428 ~~~~~~~~~~~~~~~~~~~~~~
429 All config files are fully-fledged M4 scripts, so you can use any M4 features
430 you need, the most helpful one being definition of your own macros by
432 define(`macro_name', `expansion')
434 However, there is a couple of things you need to care about:
436 o The comment character is redefined to `;'. I.e., wherever a semicolon
437 occurs, the rest of the line is a comment which is copied verbatim
438 to the output file (if the output is not suppressed like in case
439 of the cf/domains file).
441 o Names starting with 'nsc_' or spelled in all caps are reserved
442 for the NSC itself and unless documented, messing with them can
443 bring surprising results. If you need to use such a name in your
444 zone file (maybe you like to shout in your host names :-) ),
445 quote it with ` and '.
447 o Don't use commas, quotes nor parentheses in your record names.
452 convert A simple Perl script for conversion of zone files to NSC
453 domain files. Requires the Net::DNS module (available from
454 CPAN at ftp.cpan.org; present in recent versions of Perl).
455 Keep in mind that the script is very simple and its craft
456 is of a very limited kind, so check its output carefully.
458 chkdel A simple Perl script for checking of domain delegations --
459 it checks all PRIMARY and SECONDARY records in cf/domains
460 against NS records. Requires the Net::DNS module and also
461 some tweaking of parameters at the top of the script.