2 Domain Name Server Configuration Utilities -- NSC 2.99b
4 (c) 1997--2003 Martin Mares <mj@ucw.cz>
6 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
9 ------------------------------------------------------------------------------------
10 WARNING: This is a prerelease of the NSC 3.0. See NEWS for the list of changes.
11 Most importantly, the configuration files are NOT compatible with the old releases.
12 Also, it hasn't undergone much extensive testing yet, so there might be bugs around.
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 CONFIG(...) - insert user data to named.conf
141 MAKEFILE(...) - insert user data to Makefile
146 The domain files contain descriptions of all DNS records for the given
147 domain, starting with the SOA record. Again, these are M4 scripts and the
148 declarations are macro calls. Lines starting with a semicolon are treated
149 as comments and just copied to the generated zone file. Text outside
150 declarations is copied to the zone file as well, so you can spice up the NSC
151 output with your own records.
153 All host or domain names are either names relative to the current domain
154 with no dots inside or absolute names (in this case, NSC automatically
155 ensures that the trailing dot is present in the resource records). Relative
156 names with dots are not supported, but they are rare and you can always write
157 them as absolute anyway.
162 Generate a SOA record for the domain. This must be the first
163 declaration in the config file. The parameters of the SOA
164 are taken from configuration variables (see below). The
165 serial number is calculated from the version number remembered
166 in the version file, following the usual practice of encoding
167 current date and a sequence number within the current day
168 in the serial number, which is guaranteed to be strictly
169 increasing unless you perform more than 99 updates in a single
170 day (in which case NSC stops and tells you to tweak the serial
173 The SOA record otherwise acts like a sub-domain (D) declaration,
174 therefore it can be followed by other records like NS (mandatory)
178 Start declaration of a host. Doesn't generate anything, only
179 remembers the host's name.
182 Specify addresses for the current host. In the normal mode, it
183 creates A records, in the reverse mode, PTR records.
186 A shortcut for H(host) ADDR(addr...) -- in many cases everything
187 you need for a single host.
190 Like ADDR, but suppresses PTR records. (This one is useful if you
191 have a single IP address used for zillions of names and you want
192 to avoid having zillions of PTR records for the same address.)
195 A shortcut for H(host) DADDR(addr...)
198 Start declaration of a sub-domain. Technically the same as H(domain),
199 but this one should be more intuitive.
202 Specify a glue record for a name server contained within a sub-domain
203 it's a primary for. Currently it's an equivalent of DH(ns, addr...).
206 Specify a list of name server names for the current domain
207 (started by either a SOA or D declaration). Generates NS records.
210 Specify a list of mail exchangers for the current host or domain.
211 Each mail exchanger should be preceded by a priority. Generates
215 Specify a HINFO record for the current host. Very rare in the
219 Specify a list of aliases for the current host or domain.
220 Generates a series of CNAME records pointing from the aliases
221 to the current host/domain.
224 Generate a CNAME record -- "src" points to "dest".
227 Generate a PTR record -- "src" points to "dest". It's a common
228 record in reverse zones (and although it's legal in forward
229 zones as well, such use is very rare), however it's more convenient
230 to have your PTR's generated by the REVERSE directive. But if you
231 need anything special, here is the tool.
233 REVBLOCK(subdomain, min, max)
234 Generate a series of CNAME records numbered from `min' to `max'
235 and pointing to the same name in the given sub-domain, finally
236 declaring the sub-domain as well, so you can continue with its
239 Example: REVBLOCK(a, 16, 18) NS(ns.xyzzy.org) yields
246 This is a very common construct for classless reverse delegations,
247 see Section 6 for more details.
250 Switch to reverse mode. From this point on, all output is suppressed
251 except for ADDR declarations belonging to the specified network which
252 are automatically converted to PTR records.
254 With help of this feature, defining reverse zones can be as easy as:
256 ; Reverse zone for 10.0.0.0/24 a.k.a. 0.0.10.in-addr.arpa.
258 NS(ns1.example.com, ns2.example.com)
260 ; Include all primary zones containing ADDR's from this range,
261 ; which can be accomplished by a multi-file REVERSE declaration
265 4. Configuration variables
266 ~~~~~~~~~~~~~~~~~~~~~~~~~~
267 There is a fair amount of configuration variables (which are in reality normal
268 M4 macros). Each variable has a hard-wired default value which can be overridden
269 in cf/config by re-defining the variable. Also, all other config files can specify
270 their local definitions, but you need to be careful to change the variable before
271 it is used for the first time.
273 To change the setting, use
275 define(`variable', `value')
277 As usually, even this config file is a M4 script. Comments can be started by
278 semicolons, text outside macros is ignored.
280 The following variables are available:
282 NAMED_RESTART_CMD Shell command for restarting the name server daemon
283 (default: ndc restart)
285 ROOT Root directory of the whole package (default: /etc/named)
286 CFDIR Directory with config files (default: cf)
287 ZONEDIR Directory with zone files (default: zone)
288 BAKDIR Directory with backup files (default: bak)
289 VERSDIR Directory with version files (default: var)
290 ROOTCACHE File with the cache of root name servers
292 REFRESH SOA record parameters
296 NSNAME Origin server (default: hostname of your machine)
297 MAINTNAME Domain maintainer name (default: root@NSNAME)
299 BIND_OPTIONS Extra options to put to the options { ... } section of named.conf
301 For the timing parameters, the following shortcuts are available:
303 HOURS(n) Convert hours to seconds
304 MINUTES(n) Convert minutes to seconds
305 DAYS(n) Convert days to seconds
307 For the BIND_OPTIONS, we offer:
309 FORWARD(ip...) Try to ask the given name servers first to see if they
310 have the reply cached.
311 SLAVE(ip...) Pass all non-local requests to the given name servers.
316 The Makefile generated by NSC offers the following targets:
318 all (default) - update all zone files and reload the daemon
319 clean - clean all generated zone files and backups
320 clobber - clean + delete Makefile and named.conf
321 (wise to do after major reconfigurations)
322 distclean - clobber + delete all version files (use only
323 if you really know what you are doing as the
324 serial number information in newly generated
325 files might be inconsistent then).
328 6. Classless reverse delegations
329 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
330 NSC also supports classless delegations for reverse zones using the mechanism
331 described in RFC 2317, i.e. by putting CNAME records to the reverse zone which
332 point to records of the same name in a sub-domain which you can delegate directly.
334 For example if you want to delegate 64-127 in 0.0.10.in-addr.arpa to ns.example.net,
335 you create a 64/26 sub-domain (26 is the network prefix length) and add the following
336 records to 0.0.10.in-addr.arpa:
338 64 CNAME 64.64/26.0.0.10.in-addr.arpa.
339 65 CNAME 65.64/26.0.0.10.in-addr.arpa.
341 127 CNAME 127.64/26.0.0.10.in-addr.arpa.
343 64/26 NS ns.example.net.
345 Then you configure ns.example.net to be a primary name server for the zone
346 64/26.0.0.10.in-addr.arpa and put the PTR records there:
348 64 PTR sixty-four.example.net.
349 65 PTR sixty-five.example.net.
351 127 PTR two-to-seven-minus-one.example.net.
353 NSC offers special primitives for configuring such delegations, but not limited
354 to the sub-domain name syntax shown above (which is recommended by the RFC, but it's
355 far from being the only one used in the real world, other possibilities being for
356 example 64-127, 64+64 etc.).
358 The CNAME block can be generated by the REVBLOCK(subdomain-name, low-addr, high-addr)
359 directive in the configuration of the whole reverse zone. The example above would
362 REVBLOCK(64/26, 64, 127)
364 The sub-zone can be created automatically like any another reverse zone, you only
365 need to use the three-parameter form of the REVERSE directive to specify the
366 address range in order to filter out possible hosts falling outside your range.
368 CAVEAT: The slashes in zone names are automatically translated to @'s when forming
371 Again for the example above, you need to put the following to cf/domains:
373 REVERSE(10.0.0.64/26, <list-of-domains-to-gather-the-addresses-from>)
375 And to cf/64@26.0.0.10:
377 SOA(REV(10.0.0.64/26))
378 NS(<list-of-name-servers>)
379 REVERSE(10.0.0, 64, 127)
381 NOTE: It's usually helpful to configure the primary name server for the parent
382 domain (i.e., the one where you configure the delegation and create the CNAME's)
383 as a secondary for the sub-zone as well, so if it replies with the CNAME, it will
384 include the PTR record pointed to by the CNAME in the additional section of its
385 reply, eliminating the need for an extra query.
390 NSC also supports IPv6 in a pretty straightforward form: wherever you can write
391 an IPv4 address, you can use an IPv6 address as well. Incomplete IP addresses
392 or ranges used for specifying address blocks for reverse delegations are replaced
393 by network prefixes of the standard form <address>/<prefix-length>.
397 H(ianus, 1.2.3.4, fec0::1234:5678:9abc:def0)
399 specifies a dual-stack host with both an A record and an AAAA record.
401 CAVEAT: The backward-compatible IPv6 address syntax with ":v.w.x.y" at the end
402 is not supported. All other syntaxes and quirks hopefully are.
405 8. Interaction with M4
406 ~~~~~~~~~~~~~~~~~~~~~~
407 All config files are fully-fledged M4 scripts, so you can use any M4 features
408 you need, the most helpful one being definition of your own macros by
410 define(`macro_name', `expansion')
412 However, there is a couple of things you need to care about:
414 o The comment character is redefined to `;'. I.e., wherever a semicolon
415 occurs, the rest of the line is a comment which is copied verbatim
416 to the output file (if the output is not suppressed like in case
417 of the cf/domains file).
419 o Names starting with 'nsc_' or spelled in all caps are reserved
420 for the NSC itself and unless documented, messing with them can
421 bring surprising results. If you need to use such a name in your
422 zone file (maybe you like to shout in your host names :-) ),
423 quote it with ` and '.
425 o Don't use commas, quotes nor parentheses in your record names.
430 convert A simple Perl script for conversion of zone files to NSC
431 domain files. Requires the Net::DNS module (available from
432 CPAN at ftp.cpan.org; present in recent versions of Perl).
433 Keep in mind that the script is very simple and its craft
434 is of a very limited kind, so check its output carefully.
436 chkdel A simple Perl script for checking of domain delegations --
437 it checks all PRIMARY and SECONDARY records in cf/domains
438 against NS records. Requires the Net::DNS module and also
439 some tweaking of parameters at the top of the script.
441 LocalWords: MINTTL NSNAME hostname MAINTNAME