Nssync
1 Introduction
2 Overview
3 Configuration File
4 Nssync Configuration
5 Invocation
6 Exit Codes
7 How to Report a Bug
Appendix A GNU Free Documentation License
Concept Index
Nssync
1 Introduction
2 Overview
3 Configuration File
  3.1 Comments
  3.2 Pragmatic Comments
  3.3 Statements
  3.4 Preprocessor
4 Nssync Configuration
  4.1 General Settings
  4.2 SQL Access
  4.3 Synchronization Block
5 Invocation
6 Exit Codes
7 How to Report a Bug
Appendix A GNU Free Documentation License
Concept Index
Nssync
******

This edition of the 'nssync Manual', last updated 1 December 2014,
documents 'nssync' Version 1.1.91.

1 Introduction
**************

BIND, the most frequently used DNS server, normally keeps its zone data
in "zone files".  This approach becomes inconvenient when the number of
zones grows beyond a certain limit.  When this happens, the obvious
solution is to move all data to a database and make 'named' read it from
there.  Recent versions of BIND include "dynamically loadable zones"
("DLZ") feature(1), which makes it possible to use such databases
directly.  However, DLZ has problems of its own, one of them being that
it is unable to propagate glue records(2).

   The 'nssync' utility provides an alternative solution, which makes it
possible to keep your zone data in an SQL(3) database without using DLZ
and with glue records working.

   It does so by periodically polling the database to determine which
data have changed recently and converting the database into BIND zone
files.

   ---------- Footnotes ----------

   (1) See <http://bind-dlz.sourceforge.net/>.

   (2) See:
<http://permalink.gmane.org/gmane.network.dns.bind9.dlz/2078>,
<http://blog.gmane.org/gmane.network.dns.bind9.dlz/month=20110101>.

   (3) As of version 1.1.91 only MySQL is supported.

2 Overview
**********

The 'nssync' utility is normally started periodically from crontab.
Upon startup it reads its configuration file, which supplies the
necessary program settings.  Then, if the settings require so, it
verifies that no other copy of the 'nssync' is already running.  Further
on, it parses the 'named' configuration file 'named.conf' to determine
several settings needed for its further operation, in particular, the
value of the 'directory' statement in the 'options' block.

   Once these preliminary operations are over, 'nssync' starts its main
task.  Its configuration file defines, among other data, one or more
"synchronization blocks".  Each such block defines SQL statements which
return information about DNS zones as well as the location of 'named'
configuration file where the 'zone' statements for these zones are to be
stored (it is supposed that this file is included somewhere in the main
'named.conf' file).  For each synchronization block, the utility
retrieves the zone data from the database and formats them into separate
zone files.  Each of these files is then compared to an already existing
one (locations of the zone files are defined in the synchronization
block they pertain to).  If the files differ, new zone file replaces the
old one and a flag is set indicating that the 'named' daemon needs to be
restarted in order to read new configuration.

   When this stage is finished, 'nssync' reloads the name server (if
required) and exits.

   Several command line options can be supplied in order to modify the
program's behavior.  In particular, it is possible to check the
configuration file syntax or even instruct the utility to do everything,
except modifying the zone files (a so-called "dry-run mode").  This
allows you to debug your configuration before actually starting using
'nssync'.

3 Configuration File
********************

'Nssync' reads its settings from a configuration file 'nssync.conf'
located normally in the system configuration directory (usually '/etc'
or '/usr/local/etc', depending on compile-time options).

   This chapter describes the syntax of that file in general.  The
chapter that follows describes the 'nssync'-specific settings in detail.

   The configuration file consists of statements and comments.

   There are three classes of lexical tokens: keywords, values, and
separators.  Blanks, tabs, newlines and comments, collectively called
"white space" are ignored except as they serve to separate tokens.  Some
white space is required to separate otherwise adjacent keywords and
values.

3.1 Comments
============

"Comments" may appear anywhere where white space may appear in the
configuration file.  There are two kinds of comments: single-line and
multi-line comments.  "Single-line" comments start with '#' or '//' and
continue to the end of the line:

     # This is a comment
     // This too is a comment

   "Multi-line" or "C-style" comments start with the two characters '/*'
(slash, star) and continue until the first occurrence of '*/' (star,
slash).

   Multi-line comments cannot be nested.  However, single-line comments
may well appear within multi-line ones.

3.2 Pragmatic Comments
======================

Pragmatic comments are similar to usual single-line comments, except
that they cause some changes in the way the configuration is parsed.
Pragmatic comments begin with a '#' sign and end with the next physical
newline character.

'#include <FILE>'
'#include FILE'
     Include the contents of the file FILE.  If FILE is an absolute file
     name, both forms are equivalent.  Otherwise, the form with angle
     brackets searches for the file in the "include search path", while
     the second one looks for it in the current working directory first,
     and, if not found there, in the include search path.

     The default include search path is:

       1. 'PREFIX/share/nssync/1.1.91/include'
       2. 'PREFIX/share/nssync/include'

     where PREFIX is the installation prefix.

'#include_once <FILE>'
'#include_once FILE'
     Same as '#include', except that, if the FILE has already been
     included, it will not be included again.

'#line NUM'
'#line NUM "FILE"'
     This line causes the parser to believe, for purposes of error
     diagnostics, that the line number of the next source line is given
     by NUM and the current input file is named by FILE.  If the latter
     is absent, the remembered file name does not change.

'# NUM "FILE"'
     This is a special form of '#line' statement, understood for
     compatibility with the C preprocessor.

   In fact, these statements provide a rudimentary preprocessing
features.  For more sophisticated ways to modify configuration before
parsing, see *note Preprocessor::.

3.3 Statements
==============

A "simple statement" consists of a keyword and value separated by any
amount of whitespace.  Simple statement is terminated with a semicolon
(';').

   The following is a simple statement:

     standalone yes;
     pidfile /var/run/slb.pid;

   A "keyword" begins with a letter and may contain letters, decimal
digits, underscores ('_') and dashes ('-').  Examples of keywords are:
'expression', 'output-file'.

   A "value" can be one of the following:

number
     A number is a sequence of decimal digits.

boolean
     A boolean value is one of the following: 'yes', 'true', 't' or '1',
     meaning "true", and 'no', 'false', 'nil', '0' meaning "false".

unquoted string
     An unquoted string may contain letters, digits, and any of the
     following characters: '_', '-', '.', '/', '@', '*', ':'.

quoted string
     A quoted string is any sequence of characters enclosed in
     double-quotes ('"').  A backslash appearing within a quoted string
     introduces an "escape sequence", which is replaced with a single
     character according to the following rules:

     Sequence               Replaced with
     \a                     Audible bell character (ASCII 7)
     \b                     Backspace character (ASCII 8)
     \f                     Form-feed character (ASCII 12)
     \n                     Newline character (ASCII 10)
     \r                     Carriage return character (ASCII
                            13)
     \t                     Horizontal tabulation character
                            (ASCII 9)
     \v                     Vertical tabulation character
                            (ASCII 11)
     \\                     A single backslash ('\')
     \"                     A double-quote.

     Table 3.1: Backslash escapes

     In addition, the sequence '\NEWLINE' is removed from the string.
     This allows to split long strings over several physical lines,
     e.g.:

          "a long string may be\
           split over several lines"

     If the character following a backslash is not one of those
     specified above, the backslash is ignored and a warning is issued.

     Two or more adjacent quoted strings are concatenated, which gives
     another way to split long strings over several lines to improve
     readability.  The following fragment produces the same result as
     the example above:

          "a long string may be"
          " split over several lines"

Here-document
     A "here-document" is a special construct that allows to introduce
     strings of text containing embedded newlines.

     The '<<WORD' construct instructs the parser to read all the
     following lines up to the line containing only WORD, with possible
     trailing blanks.  Any lines thus read are concatenated together
     into a single string.  For example:

          <<EOT
          A multiline
          string
          EOT

     The body of a here-document is interpreted the same way as a
     double-quoted string, unless WORD is preceded by a backslash (e.g.
     '<<\EOT') or enclosed in double-quotes, in which case the text is
     read as is, without interpretation of escape sequences.

     If WORD is prefixed with '-' (a dash), then all leading tab
     characters are stripped from input lines and the line containing
     WORD.  Furthermore, if '-' is followed by a single space, all
     leading whitespace is stripped from them.  This allows to indent
     here-documents in a natural fashion.  For example:

          <<- TEXT
              The leading whitespace will be
              ignored when reading these lines.
          TEXT

     It is important that the terminating delimiter be the only token on
     its line.  The only exception to this rule is allowed if a
     here-document appears as the last element of a statement.  In this
     case a semicolon can be placed on the same line with its
     terminating delimiter, as in:

          help-text <<-EOT
                  A sample help text.
          EOT;

list
     A "list" is a comma-separated list of values.  Lists are enclosed
     in parentheses.  The following example shows a statement whose
     value is a list of strings:

          alias (test,null);

     In any case where a list is appropriate, a single value is allowed
     without being a member of a list: it is equivalent to a list with a
     single member.  This means that, e.g.

          alias test;

     is equivalent to

          alias (test);

   A "block statement" introduces a logical group of statements.  It
consists of a keyword, followed by an optional value, and a sequence of
statements enclosed in curly braces, as shown in the example below:

     server srv1 {
       host 10.0.0.1;
       community "foo";
     }

   The closing curly brace may be followed by a semicolon, although this
is not required.

3.4 Preprocessor
================

Before actual parsing, the configuration file is preprocessed.  The
built-in preprocessor handles only file inclusion and '#line' statements
(*note Pragmatic Comments::), while the rest of traditional
preprocessing facilities, such as macro expansion, is supported via
'm4', which serves as external preprocessor.

   The detailed description of 'm4' facilities lies far beyond the scope
of this document.  You will find a complete user manual in *note GNU M4
manual: (m4)Top.  For the rest of this subsection we assume the reader
is sufficiently acquainted with 'm4' macro processor.

   The external preprocessor is invoked with '-s' flag, which instructs
it to include line synchronization information in its output.  This
information is then used by the parser to display meaningful diagnostic.

   An initial set of macro definitions is supplied by the 'pp-setup'
file, located in 'PREFIX/share/nssync/1.1.91/include' directory.

   The default 'pp-setup' file renames all 'm4' built-in macro names so
they all start with the prefix 'm4_'.  This is similar to GNU m4
'--prefix-builtin' option, but has an advantage that it works with
non-GNU 'm4' implementations as well.

4 Nssync Configuration
**********************

4.1 General Settings
====================

These settings modify the behavior of 'nssync' as a whole.

 -- Configuration: pidfile FILE
     At startup, check if FILE already exists and is owned by an
     existing process.  Exit if so.  Use this statement to avoid
     accidentally running two copies of 'nssync' simultaneously.

 -- Configuration: tempdir DIR
     Sets the name for the temporary directory.  This is a directory
     where 'nssync' creates temporary zone files.  The argument must
     point to an existing directory.

 -- Configuration: check-ns BOOL
     If set to 'true', 'nssync' will check the list of NS servers prior
     to creating a zone file.  The file will be created only if IPv4
     address of one of the servers matches one of the IP addresses of
     the host on which 'nssync' is run.

 -- Configuration: named-conf FILE
     Defines the full pathname of the 'named' configuration file.
     Default is '/etc/named.conf'.

 -- Configuration: bind-include-path LIST
     Sets include search path for 'include' directives found in BIND
     configuration.  The argument is either a single directory or a list
     of directories (*note list: Statements.).

 -- Configuration: zonefile-pattern PAT
     Defines the pattern for zone file names.  The name of each zone
     file is created by expanding variable references in the PAT
     argument.  The following variable references are defined:

     $zone
     ${zone}
          Name of the zone, without the trailing dot.

     $synctag
     ${synctag}
          Zone synchronization tag (*note Synchronization Block::).

     Both notations (with and without braces) are equivalent.  The
     notation with curly braces should be used if the reference is
     immediately followed by a letter.

     The default zone file pattern is '$zone.$synctag'.

 -- Configuration: zone-conf PAT
     Defines the pattern for "zone configuration file", i.e.  a file
     containing 'zone' statements.

     The handling of PAT is similar to that in 'zonefile-pattern',
     except that only the '$synctag' reference is defined.

 -- Configuration: compare-command CMD
     Defines a command to be used for comparing two zone files.  The CMD
     must be a command taking two files as its arguments and returning 0
     if they are the same or non-zero if they differ.  'Nssync' uses
     this command to determine whether a particular zone has changed.
     The following "variable references" are expanded in CMD:

     $oldfile
     ${oldfile}
          Old zone file.

     $newfile
     ${newfile}
          New zone file.

     The default 'compare-command' value is:

          cmp $oldfile $newfile > /dev/null

 -- Configuration: reload-command CMD
     Defines a command to reload the nameserver.  The default is
     '/usr/sbin/rndc reload'.

4.2 SQL Access
==============

The following statements define the database server and the database to
use:

 -- Configuration: host HOSTNAME[:PORT-OR-SOCKET]
     Defines the SQL server IP and port.  The HOSTNAME can be either the
     server IP address or its hostname.  The PORT-OR-SOCKET part, if
     supplied, can be either the number of TCP port to use instead of
     the default 3306 or the full pathname of the UNIX socket.  In the
     latter case HOSTNAME is effectively ignored.

 -- Configuration: database NAME
     Sets the database name.

 -- Configuration: ssl-ca FILE
     Defines the name of the Certificate Authority (CA) file.

   There are two ways to supply database access credentials.  The
simplest one is by using 'user' and 'password' statements:

 -- Configuration: user NAME
     Sets SQL user name.

 -- Configuration: password ARG
     Sets SQL user password.

   The drawback of this approach is that the password appears in
plaintext, which means the permissions of the 'nssync.conf' file must be
tightened so as to avoid its compromise.

   The following two statements provide an alternative, more safe and
flexible way of setting access credentials:

 -- Configuration: sql-config-file FILE
     Read MySQL configuration from the "option file" FILE.  *Note Using
     Option Files: (mysql)option-files, for a description of MySQL
     option file format.

 -- Configuration: sql-config-group NAME
     Read the named group from the SQL configuration file.

   To illustrate their use, suppose your 'nssync.conf' file contains the
following:

     sql-config-file /etc/nssync.my;
     sql-config-group nssync;

   The the '/etc/nssync.my' will contain the actual SQL access
configuration, which can look as in the example below:

     [nssync]
     socket = /var/db/mysql.sock
     database = dns
     user = root
     pass = guessme

 -- Configuration: slave-status-file FILE
     Use this statement if 'nssync' reads data from a slave database.
     It allows you to avoid recreating zone files if the database
     information has not changed since the previous run.

     If this statement is present, 'nssync' will save the state of the
     SQL slave in FILE.  Upon startup, it will read these data and
     compare them with the current state.  If they are the same, it will
     exit immediately.

4.3 Synchronization Block
=========================

A "synchronization block" defines a set of zones to be synchronized from
the database and configures SQL statements which return the zone data.
This set is identified by "synchronization tag", supplied as the
argument to the 'sync' statement:

     # Define a synchronization block.
     sync TAG {
       # zone configuration file
       zone-conf PAT;
       # pattern for new zone file names
       zonefile-pattern PAT;
       # add these statements to each generated zone file
       add-statements TEXT;
       # a query for retrieving SOA records
       soa-query STRING;
       # a query for retrieving NS and similar records
       ns-query STRING;
       # a query for retrieving the rest of RRs
       rr-query STRING;
       # a query for retrieving RRs from reverse delegation zones
       rev-rr-query STRING;
     }

   Statements within the 'sync' block configure the zones:

 -- Configuration: zone-conf PAT
     Defines the pattern for the name of zone configuration file for
     zones in this synchronization block.  If not supplied, the global
     'zone-conf' statement will be used instead (*note zone-conf::).

 -- Configuration: zonefile-pattern PAT
     Defines the pattern for zone file names.  If not supplied, the
     global 'zonefile-pattern' statement will be used instead (*note
     zonefile-pattern::).

 -- Configuration: add-statements TEXT
     Append TEXT to each generated zone statement.  For example, the
     following can be used to redefine forwarders and query ACLs for
     zones in this synchronization block:

          add-statements <<EOT
            forwarders { /* empty */ };
            allow-query { local-query-only; };
          EOT;

     Notice the use of the "here-document" construct.

   The following statements define which zones pertain to this
particular synchronization block:

 -- Configuration: soa-query STRING
     A query for retrieving SOA records.

 -- Configuration: ns-query STRING
     A query for retrieving NS and similar records.  Use the '$zone'
     reference for the zone name.

 -- Configuration: rr-query STRING
     A query for retrieving the rest of RRs.  Use the '$zone' reference
     for the zone name.

 -- Configuration: rev-rr-query STRING
     A query for retrieving RRs from reverse delegation zones.  Use the
     '$zone' reference for the zone name.

   Here is an example of a working 'sync' directive:

     sync external {
       zone-conf "/var/namedb/nssync/zones.external";
       zonefile-pattern "/var/namedb/external/db.${zone}";

       soa-query    "select zone, ttl, type, data, resp_person, "
                    "serial, refresh, retry, expire, minimum "
                    "from dns_soa where type='SOA' "
                    "and view='external' order by zone";

       ns-query     "select ttl, type, data "
                    "from dns_soa where zone='$zone' "
                    "and type<>'SOA' and view='external'";

       rr-query     "select host, ttl, type, mx_priority, "
                    "case when type='TXT' then "
                    "concat('\"', data, '\"') "
                    "else data end "
                    "from dns_records "
                    "where zone='$zone' and view='external' "
                    "order by 1";

       rev-rr-query "select host, ttl, type, mx_priority, "
                    "case when type='TXT' then "
                    "concat('\"', data, '\"') "
                    "else data end "
                    "from dns_records "
                    "where zone='$zone' and view='external' "
                    "order by cast(host as unsigned)";
     }

5 Invocation
************

The 'nssync' is normally invoked periodically from a crontab, e.g.:

     */5 * * * *  /usr/sbin/nssync | \
       /usr/bin/logger -t nssync -p local1.err

   The following table summarizes available command line options:

'-E'
     Preprocess configuration file and exit.

'-c FILE'
'--config-file=FILE'
     Use FILE instead of the default configuration file.

'-f'
'--force'
     Proceed even if slave status has not changed (*note
     slave-status-file::).

'-n'
'--dry-run'
     Do nothing, print almost everything; implies '--debug --stderr'.
     Use additional '--debug' options to get even more info.

'-t'
'--lint'
     Parse configuration file and exit.  The return status is 0 if the
     syntax is OK, and 78 if errors were detected (*note Exit Codes::).

'-D SYMBOL=VALUE'
'--define=SYMBOL[=VALUE]'
     Define a preprocessor symbol.

'-I DIR'
'--include-directory=DIR'
     Add include directory.

'--no-preprocessor'
     Disable preprocessing.

'--preprocessor=COMMAND'
     Use COMMAND instead of the default preprocessor.

'-d'
'--debug'
     Increase debug level.

'-X'
'--debug-lexer'
     Debug configuration file lexer.

'-x'
'--debug-parser'
     Debug configuration file parser.

'--config-help'
     Show configuration file summary

'-V'
'--version'
     Print program version.

'-h'
'--help'
     Give this help list.

'--usage'
     Give a short usage message.

6 Exit Codes
************

Apart from issuing a descriptive error message, 'nssync' attempts to
indicate the reason of its termination by its error code.  As usual, a
zero exit code indicates normal termination.  The table below summarizes
all possible error codes.  For each error code, it indicates its decimal
value and its symbolic name from 'include/sysexits.h' (if available).

0
EX_OK
     Program terminated correctly.

64
EX_USAGE
     The program was invoked incorrectly, e.g.  an invalid option was
     given, or an erroneous argument was supplied to an option.

69
EX_UNAVAILABLE
     The program exited due to some error not otherwise described in
     this table.

70
EX_SOFTWARE
     Some internal software error occurred.

78
EX_CONFIG
     An error in the configuration file was detected.

7 How to Report a Bug
*********************

Email bug reports to <gray+nssync@gnu.org.ua>.  Please include a
detailed description of the bug and information about the conditions
under which it occurs, so we can reproduce it.  To facilitate the task,
the following list shows the basic set of information that is needed in
order to find the bug:

   * Package version you use.
   * A detailed description of the bug.
   * Conditions under which the bug appears.
   * It is often helpful to send the contents of 'config.log' file along
     with your bug report.  This file is created after running
     './configure' in the 'nssync' source root directory.

Appendix A GNU Free Documentation License
*****************************************

                     Version 1.3, 3 November 2008

     Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
     <http://fsf.org/>

     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

  0. PREAMBLE

     The purpose of this License is to make a manual, textbook, or other
     functional and useful document "free" in the sense of freedom: to
     assure everyone the effective freedom to copy and redistribute it,
     with or without modifying it, either commercially or
     noncommercially.  Secondarily, this License preserves for the
     author and publisher a way to get credit for their work, while not
     being considered responsible for modifications made by others.

     This License is a kind of "copyleft", which means that derivative
     works of the document must themselves be free in the same sense.
     It complements the GNU General Public License, which is a copyleft
     license designed for free software.

     We have designed this License in order to use it for manuals for
     free software, because free software needs free documentation: a
     free program should come with manuals providing the same freedoms
     that the software does.  But this License is not limited to
     software manuals; it can be used for any textual work, regardless
     of subject matter or whether it is published as a printed book.  We
     recommend this License principally for works whose purpose is
     instruction or reference.

  1. APPLICABILITY AND DEFINITIONS

     This License applies to any manual or other work, in any medium,
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     To "Preserve the Title" of such a section when you modify the
     Document means that it remains a section "Entitled XYZ" according
     to this definition.

     The Document may include Warranty Disclaimers next to the notice
     which states that this License applies to the Document.  These
     Warranty Disclaimers are considered to be included by reference in
     this License, but only as regards disclaiming warranties: any other
     implication that these Warranty Disclaimers may have is void and
     has no effect on the meaning of this License.

  2. VERBATIM COPYING

     You may copy and distribute the Document in any medium, either
     commercially or noncommercially, provided that this License, the
     copyright notices, and the license notice saying this License
     applies to the Document are reproduced in all copies, and that you
     add no other conditions whatsoever to those of this License.  You
     may not use technical measures to obstruct or control the reading
     or further copying of the copies you make or distribute.  However,
     you may accept compensation in exchange for copies.  If you
     distribute a large enough number of copies you must also follow the
     conditions in section 3.

     You may also lend copies, under the same conditions stated above,
     and you may publicly display copies.

  3. COPYING IN QUANTITY

     If you publish printed copies (or copies in media that commonly
     have printed covers) of the Document, numbering more than 100, and
     the Document's license notice requires Cover Texts, you must
     enclose the copies in covers that carry, clearly and legibly, all
     these Cover Texts: Front-Cover Texts on the front cover, and
     Back-Cover Texts on the back cover.  Both covers must also clearly
     and legibly identify you as the publisher of these copies.  The
     front cover must present the full title with all words of the title
     equally prominent and visible.  You may add other material on the
     covers in addition.  Copying with changes limited to the covers, as
     long as they preserve the title of the Document and satisfy these
     conditions, can be treated as verbatim copying in other respects.

     If the required texts for either cover are too voluminous to fit
     legibly, you should put the first ones listed (as many as fit
     reasonably) on the actual cover, and continue the rest onto
     adjacent pages.

     If you publish or distribute Opaque copies of the Document
     numbering more than 100, you must either include a machine-readable
     Transparent copy along with each Opaque copy, or state in or with
     each Opaque copy a computer-network location from which the general
     network-using public has access to download using public-standard
     network protocols a complete Transparent copy of the Document, free
     of added material.  If you use the latter option, you must take
     reasonably prudent steps, when you begin distribution of Opaque
     copies in quantity, to ensure that this Transparent copy will
     remain thus accessible at the stated location until at least one
     year after the last time you distribute an Opaque copy (directly or
     through your agents or retailers) of that edition to the public.

     It is requested, but not required, that you contact the authors of
     the Document well before redistributing any large number of copies,
     to give them a chance to provide you with an updated version of the
     Document.

  4. MODIFICATIONS

     You may copy and distribute a Modified Version of the Document
     under the conditions of sections 2 and 3 above, provided that you
     release the Modified Version under precisely this License, with the
     Modified Version filling the role of the Document, thus licensing
     distribution and modification of the Modified Version to whoever
     possesses a copy of it.  In addition, you must do these things in
     the Modified Version:

       A. Use in the Title Page (and on the covers, if any) a title
          distinct from that of the Document, and from those of previous
          versions (which should, if there were any, be listed in the
          History section of the Document).  You may use the same title
          as a previous version if the original publisher of that
          version gives permission.

       B. List on the Title Page, as authors, one or more persons or
          entities responsible for authorship of the modifications in
          the Modified Version, together with at least five of the
          principal authors of the Document (all of its principal
          authors, if it has fewer than five), unless they release you
          from this requirement.

       C. State on the Title page the name of the publisher of the
          Modified Version, as the publisher.

       D. Preserve all the copyright notices of the Document.

       E. Add an appropriate copyright notice for your modifications
          adjacent to the other copyright notices.

       F. Include, immediately after the copyright notices, a license
          notice giving the public permission to use the Modified
          Version under the terms of this License, in the form shown in
          the Addendum below.

       G. Preserve in that license notice the full lists of Invariant
          Sections and required Cover Texts given in the Document's
          license notice.

       H. Include an unaltered copy of this License.

       I. Preserve the section Entitled "History", Preserve its Title,
          and add to it an item stating at least the title, year, new
          authors, and publisher of the Modified Version as given on the
          Title Page.  If there is no section Entitled "History" in the
          Document, create one stating the title, year, authors, and
          publisher of the Document as given on its Title Page, then add
          an item describing the Modified Version as stated in the
          previous sentence.

       J. Preserve the network location, if any, given in the Document
          for public access to a Transparent copy of the Document, and
          likewise the network locations given in the Document for
          previous versions it was based on.  These may be placed in the
          "History" section.  You may omit a network location for a work
          that was published at least four years before the Document
          itself, or if the original publisher of the version it refers
          to gives permission.

       K. For any section Entitled "Acknowledgements" or "Dedications",
          Preserve the Title of the section, and preserve in the section
          all the substance and tone of each of the contributor
          acknowledgements and/or dedications given therein.

       L. Preserve all the Invariant Sections of the Document, unaltered
          in their text and in their titles.  Section numbers or the
          equivalent are not considered part of the section titles.

       M. Delete any section Entitled "Endorsements".  Such a section
          may not be included in the Modified Version.

       N. Do not retitle any existing section to be Entitled
          "Endorsements" or to conflict in title with any Invariant
          Section.

       O. Preserve any Warranty Disclaimers.

     If the Modified Version includes new front-matter sections or
     appendices that qualify as Secondary Sections and contain no
     material copied from the Document, you may at your option designate
     some or all of these sections as invariant.  To do this, add their
     titles to the list of Invariant Sections in the Modified Version's
     license notice.  These titles must be distinct from any other
     section titles.

     You may add a section Entitled "Endorsements", provided it contains
     nothing but endorsements of your Modified Version by various
     parties--for example, statements of peer review or that the text
     has been approved by an organization as the authoritative
     definition of a standard.

     You may add a passage of up to five words as a Front-Cover Text,
     and a passage of up to 25 words as a Back-Cover Text, to the end of
     the list of Cover Texts in the Modified Version.  Only one passage
     of Front-Cover Text and one of Back-Cover Text may be added by (or
     through arrangements made by) any one entity.  If the Document
     already includes a cover text for the same cover, previously added
     by you or by arrangement made by the same entity you are acting on
     behalf of, you may not add another; but you may replace the old
     one, on explicit permission from the previous publisher that added
     the old one.

     The author(s) and publisher(s) of the Document do not by this
     License give permission to use their names for publicity for or to
     assert or imply endorsement of any Modified Version.

  5. COMBINING DOCUMENTS

     You may combine the Document with other documents released under
     this License, under the terms defined in section 4 above for
     modified versions, provided that you include in the combination all
     of the Invariant Sections of all of the original documents,
     unmodified, and list them all as Invariant Sections of your
     combined work in its license notice, and that you preserve all
     their Warranty Disclaimers.

     The combined work need only contain one copy of this License, and
     multiple identical Invariant Sections may be replaced with a single
     copy.  If there are multiple Invariant Sections with the same name
     but different contents, make the title of each such section unique
     by adding at the end of it, in parentheses, the name of the
     original author or publisher of that section if known, or else a
     unique number.  Make the same adjustment to the section titles in
     the list of Invariant Sections in the license notice of the
     combined work.

     In the combination, you must combine any sections Entitled
     "History" in the various original documents, forming one section
     Entitled "History"; likewise combine any sections Entitled
     "Acknowledgements", and any sections Entitled "Dedications".  You
     must delete all sections Entitled "Endorsements."

  6. COLLECTIONS OF DOCUMENTS

     You may make a collection consisting of the Document and other
     documents released under this License, and replace the individual
     copies of this License in the various documents with a single copy
     that is included in the collection, provided that you follow the
     rules of this License for verbatim copying of each of the documents
     in all other respects.

     You may extract a single document from such a collection, and
     distribute it individually under this License, provided you insert
     a copy of this License into the extracted document, and follow this
     License in all other respects regarding verbatim copying of that
     document.

  7. AGGREGATION WITH INDEPENDENT WORKS

     A compilation of the Document or its derivatives with other
     separate and independent documents or works, in or on a volume of a
     storage or distribution medium, is called an "aggregate" if the
     copyright resulting from the compilation is not used to limit the
     legal rights of the compilation's users beyond what the individual
     works permit.  When the Document is included in an aggregate, this
     License does not apply to the other works in the aggregate which
     are not themselves derivative works of the Document.

     If the Cover Text requirement of section 3 is applicable to these
     copies of the Document, then if the Document is less than one half
     of the entire aggregate, the Document's Cover Texts may be placed
     on covers that bracket the Document within the aggregate, or the
     electronic equivalent of covers if the Document is in electronic
     form.  Otherwise they must appear on printed covers that bracket
     the whole aggregate.

  8. TRANSLATION

     Translation is considered a kind of modification, so you may
     distribute translations of the Document under the terms of section
     4.  Replacing Invariant Sections with translations requires special
     permission from their copyright holders, but you may include
     translations of some or all Invariant Sections in addition to the
     original versions of these Invariant Sections.  You may include a
     translation of this License, and all the license notices in the
     Document, and any Warranty Disclaimers, provided that you also
     include the original English version of this License and the
     original versions of those notices and disclaimers.  In case of a
     disagreement between the translation and the original version of
     this License or a notice or disclaimer, the original version will
     prevail.

     If a section in the Document is Entitled "Acknowledgements",
     "Dedications", or "History", the requirement (section 4) to
     Preserve its Title (section 1) will typically require changing the
     actual title.

  9. TERMINATION

     You may not copy, modify, sublicense, or distribute the Document
     except as expressly provided under this License.  Any attempt
     otherwise to copy, modify, sublicense, or distribute it is void,
     and will automatically terminate your rights under this License.

     However, if you cease all violation of this License, then your
     license from a particular copyright holder is reinstated (a)
     provisionally, unless and until the copyright holder explicitly and
     finally terminates your license, and (b) permanently, if the
     copyright holder fails to notify you of the violation by some
     reasonable means prior to 60 days after the cessation.

     Moreover, your license from a particular copyright holder is
     reinstated permanently if the copyright holder notifies you of the
     violation by some reasonable means, this is the first time you have
     received notice of violation of this License (for any work) from
     that copyright holder, and you cure the violation prior to 30 days
     after your receipt of the notice.

     Termination of your rights under this section does not terminate
     the licenses of parties who have received copies or rights from you
     under this License.  If your rights have been terminated and not
     permanently reinstated, receipt of a copy of some or all of the
     same material does not give you any rights to use it.

  10. FUTURE REVISIONS OF THIS LICENSE

     The Free Software Foundation may publish new, revised versions of
     the GNU Free Documentation License from time to time.  Such new
     versions will be similar in spirit to the present version, but may
     differ in detail to address new problems or concerns.  See
     <http://www.gnu.org/copyleft/>.

     Each version of the License is given a distinguishing version
     number.  If the Document specifies that a particular numbered
     version of this License "or any later version" applies to it, you
     have the option of following the terms and conditions either of
     that specified version or of any later version that has been
     published (not as a draft) by the Free Software Foundation.  If the
     Document does not specify a version number of this License, you may
     choose any version ever published (not as a draft) by the Free
     Software Foundation.  If the Document specifies that a proxy can
     decide which future versions of this License can be used, that
     proxy's public statement of acceptance of a version permanently
     authorizes you to choose that version for the Document.

  11. RELICENSING

     "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
     World Wide Web server that publishes copyrightable works and also
     provides prominent facilities for anybody to edit those works.  A
     public wiki that anybody can edit is an example of such a server.
     A "Massive Multiauthor Collaboration" (or "MMC") contained in the
     site means any set of copyrightable works thus published on the MMC
     site.

     "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
     license published by Creative Commons Corporation, a not-for-profit
     corporation with a principal place of business in San Francisco,
     California, as well as future copyleft versions of that license
     published by that same organization.

     "Incorporate" means to publish or republish a Document, in whole or
     in part, as part of another Document.

     An MMC is "eligible for relicensing" if it is licensed under this
     License, and if all works that were first published under this
     License somewhere other than this MMC, and subsequently
     incorporated in whole or in part into the MMC, (1) had no cover
     texts or invariant sections, and (2) were thus incorporated prior
     to November 1, 2008.

     The operator of an MMC Site may republish an MMC contained in the
     site under CC-BY-SA on the same site at any time before August 1,
     2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents
====================================================

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:

       Copyright (C)  YEAR  YOUR NAME.
       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.3
       or any later version published by the Free Software Foundation;
       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
       Texts.  A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

   If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts."  line with this:

         with the Invariant Sections being LIST THEIR TITLES, with
         the Front-Cover Texts being LIST, and with the Back-Cover Texts
         being LIST.

   If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

   If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of free
software license, such as the GNU General Public License, to permit
their use in free software.

Concept Index
*************

This is a general index of all issues discussed in this manual.

* Menu:

* #include:                              Pragmatic Comments.  (line 142)
* #include_once:                         Pragmatic Comments.  (line 157)
* #line:                                 Pragmatic Comments.  (line 162)
* add-statements:                        Synchronization Block.
                                                              (line 529)
* bind-include-path:                     General Settings.    (line 369)
* block statement:                       Statements.          (line 303)
* boolean value:                         Statements.          (line 199)
* check-ns:                              General Settings.    (line 359)
* Comments in a configuration file:      Comments.            (line 119)
* comments, pragmatic:                   Pragmatic Comments.  (line 137)
* compare-command:                       General Settings.    (line 400)
* configuration file statements:         Statements.          (line 180)
* database:                              SQL Access.          (line 436)
* escape sequence:                       Statements.          (line 207)
* here-document:                         Statements.          (line 247)
* host:                                  SQL Access.          (line 429)
* list:                                  Statements.          (line 287)
* m4:                                    Preprocessor.        (line 318)
* multi-line comments:                   Comments.            (line 127)
* named-conf:                            General Settings.    (line 365)
* ns-query:                              Synchronization Block.
                                                              (line 547)
* nssync.conf:                           Configuration File.  (line 101)
* password:                              SQL Access.          (line 448)
* pidfile:                               General Settings.    (line 349)
* 'pp-setup':                            Preprocessor.        (line 329)
* pragmatic comments:                    Pragmatic Comments.  (line 137)
* preprocessor:                          Preprocessor.        (line 318)
* quoted string:                         Statements.          (line 207)
* reload-command:                        General Settings.    (line 419)
* rev-rr-query:                          Synchronization Block.
                                                              (line 555)
* rr-query:                              Synchronization Block.
                                                              (line 551)
* simple statements:                     Statements.          (line 180)
* single-line comments:                  Comments.            (line 119)
* slave-status-file:                     SQL Access.          (line 481)
* soa-query:                             Synchronization Block.
                                                              (line 544)
* sql-config-file:                       SQL Access.          (line 458)
* sql-config-group:                      SQL Access.          (line 463)
* ssl-ca:                                SQL Access.          (line 439)
* statement, block:                      Statements.          (line 303)
* statement, simple:                     Statements.          (line 180)
* statements, configuration file:        Statements.          (line 180)
* string, quoted:                        Statements.          (line 207)
* string, unquoted:                      Statements.          (line 203)
* sync:                                  Synchronization Block.
                                                              (line 494)
* synchronization block:                 Overview.            (line  74)
* synchronization block <1>:             Synchronization Block.
                                                              (line 494)
* synchronization tag:                   Synchronization Block.
                                                              (line 494)
* tempdir:                               General Settings.    (line 354)
* user:                                  SQL Access.          (line 445)
* zone-conf:                             General Settings.    (line 393)
* zone-conf <1>:                         Synchronization Block.
                                                              (line 519)
* zonefile-pattern:                      General Settings.    (line 374)
* zonefile-pattern <1>:                  Synchronization Block.
                                                              (line 524)