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  <chapter id="intro">
    <title>Introduction</title>
    <para>
      Kea is the next generation of DHCP software developed by ISC.
      It supports both DHCPv4 and DHCPv6 protocols along with their
      extensions, e.g. prefix delegation and dynamic updates to DNS.
    </para>

    <para>
      Kea was initially developed as a part of the BIND 10 framework
      (<ulink url="http://bind10.isc.org"/>). In early 2014, ISC
      made the decision to discontinue active development of BIND 10 and
      continue development of Kea as standalone DHCP software. As a result,
      the components and libraries related to the BIND10 framework and DNS
      are going to be removed from the Kea source tree over time.
      In order to remove the dependency on Python 3, the BIND 10 framework
      will be replaced by the server startup and configuration mechanisms
      written in C++.
    </para>

    <note>
      <simpara>Kea was implemented in the BIND 10 framework and to certain extent
      still depends on various BIND 10 libraries. It also requires the BIND 10
      framework to run, because the BIND 10 configuration mechanisms are used to
      configure Kea. As a result, this document still refers to BIND 10 in many
      paragraphs. The term "BIND 10" in the context of this document means
      "BIND 10 libraries and applications which are necessary for Kea to run
      and configure". The term "Kea" means "the collection of binaries and libraries
      which, as a whole, implement the DHCP protocols".
      </simpara>
    </note>

    <para>
      This guide covers Kea version &__VERSION__;.
    </para>

    <section>
      <title>Supported Platforms</title>
      <para>
        Kea is officially supported on RedHat Enterprise Linux,
	CentOS, Fedora and FreeBSD systems. It is also likely to work on many
	other platforms: builds have been tested on (in no particular order)
        Debian GNU/Linux 6 and unstable, Ubuntu 9.10, NetBSD 5,
        Solaris 10 and 11, FreeBSD 7 and 8, CentOS Linux 5.3,
        MacOS 10.6 and 10.7, and OpenBSD 5.1. Non supported systems
	(especially non-Linux) are likely to have issues with directly
	connected DHCPv4 clients.
      </para>
      <para>There are currently no plans to port Kea to Windows platforms.</para>
    </section>

    <section id="required-software">
      <title>Required Software at Run-time</title>

      <para>
        Running Kea uses various extra software which may
        not be provided in the default installation of some operating systems,
        nor in the standard package collections. You may
        need to install this required software separately.
        (For the build requirements, also see
        <xref linkend="build-requirements"/>.)
      </para>

      <itemizedlist>
        <listitem>
            <simpara>
        Kea was developed as a collection of applications within BIND
        10 framework and it still relies on the remaining parts of
        this framework. In particular, the servers' configuration and
        startup are still facilitated by the modules which originate
        in BIND 10. These modules require at least Python 3.1 to run.
        They also work with Python 3.2, 3.3 or 3.4 (<ulink
        url="http://www.python.org/"/>). The dependency on Python will
        be removed once replacement configuration and startup
        mechanisms are developed and released as Kea 0.9. At this
        point Kea will be written in pure C++.
            </simpara>
        </listitem>

        <listitem>
            <simpara>
        Kea supports two crypto libraries: Botan and OpenSSL. Only one of them
        is required during compilation. Kea uses the Botan crypto library for
        C++ (<ulink url="http://botan.randombit.net/"/>), version 1.8 or
        later. As an alternative to Botan, Kea can use the OpenSSL crypto
        library (<ulink url="http://www.openssl.org/"/>).  It requires a version
        with SHA-2 support.
            </simpara>
        </listitem>

        <listitem>
            <simpara>
        Kea uses the log4cplus C++ logging library
        (<ulink url="http://log4cplus.sourceforge.net/"/>).
        It requires at least log4cplus version 1.0.3.
            </simpara>
        </listitem>

        <listitem>
            <simpara>
	In order to store lease information in a MySQL database, Kea requires MySQL
    headers and libraries.  This is an optional dependency in that Kea can be
    built without MySQL support.
            </simpara>
        </listitem>

        <listitem>
            <simpara>
	In order to store lease information in a PostgreSQL database, Kea requires PostgreSQL
    headers and libraries.  This is an optional dependency in that Kea can be
    built without PostgreSQL support.
            </simpara>
        </listitem>
      </itemizedlist>
    </section>

    <section id="starting_stopping">
      <title>Starting and Stopping the Server</title>
      <!-- @todo: Rewrite this section after #3422 is done -->
      <para>
        Kea is modular.  Part of this modularity is
        accomplished using multiple cooperating processes which, together,
        provide the server functionality.
      </para>

      <!-- @todo: Rename processes here, once they are renamed in the source -->
      <para>
        At first, running many different processes may seem confusing.
        However, these processes are started by running a single
	command, <command>bind10</command>.  This command starts
	a master process, <command>b10-init</command>, which will
	start other required processes and other processes when
	configured.  The processes that may be started have names
	starting with "kea-", including:
      </para>

      <para>

        <itemizedlist>

          <listitem>
            <simpara>
              <command>b10-cfgmgr</command> &mdash;
              Configuration manager.
              This process maintains all of the configuration for BIND 10.
            </simpara>
          </listitem>

          <listitem>
            <simpara>
              <command>b10-cmdctl</command> &mdash;
              Command and control service.
              This process allows external control of the BIND 10 system.
            </simpara>
          </listitem>

          <listitem>
            <simpara>
              <command>kea-dhcp4</command> &mdash;
              DHCPv4 server process.
              This process responds to DHCPv4 queries from clients.
            </simpara>
          </listitem>

          <listitem>
            <simpara>
              <command>kea-dhcp6</command> &mdash;
              DHCPv6 server process.
              This process responds to DHCPv6 queries from clients.
            </simpara>
          </listitem>

          <listitem>
            <simpara>
              <command>kea-dhcp-ddns</command> &mdash;
              DHCP-DDNS process.
              This process acts as an intermediary between the DHCP servers
              and DNS server. It receives name update requests from the DHCP
              servers and sends DNS Update messages to the DNS servers.
            </simpara>
          </listitem>

          <listitem>
            <simpara>
              <command>b10-msgq</command> &mdash;
              Message bus daemon.
              This process coordinates communication between all of the other
              BIND 10 processes.
            </simpara>
          </listitem>

          <listitem>
            <simpara>
              <command>kea-sockcreator</command> &mdash;
              Socket creator daemon.
              This process creates sockets used by
              network-listening BIND 10 processes.
            </simpara>
          </listitem>

          <listitem>
            <simpara>
              <command>b10-stats</command> &mdash;
              Statistics collection daemon.
              This process collects and reports statistics data.
            </simpara>
          </listitem>

          <listitem>
            <simpara>
              <command>b10-stats-httpd</command> &mdash;
              HTTP server for statistics reporting.
              This process reports statistics data in XML format over HTTP.
            </simpara>
          </listitem>

        </itemizedlist>
      </para>

      <para>
        These do not need to be manually started independently.
      </para>

    </section>

    <section id="managing_once_running">
      <title>Managing BIND 10</title>
      <!-- @todo: Rewrite this section after #3422 is done -->

      <para>
        Once BIND 10 is running, a few commands are used to interact
        directly with the system:
        <itemizedlist>
          <listitem>
            <simpara>
              <command>bindctl</command> &mdash;
              Interactive administration interface.
              This is a low-level command-line tool which allows
              a developer or an experienced administrator to control
              Kea.
            </simpara>
          </listitem>
          <listitem>
            <simpara>
              <command>b10-cmdctl-usermgr</command> &mdash;
              User access control.
              This tool allows an administrator to authorize additional users
              to manage Kea.
            </simpara>
          </listitem>
  <!-- TODO usermgr -->
        </itemizedlist>
      </para>
    </section>

    <para>
      The tools and modules are covered in full detail in this guide.
<!-- TODO point to these -->
      In addition, manual pages are also provided in the default installation.
    </para>

<!--
bin/
  bindctl*
  host*
lib/
  libauth
  libdns
  libexceptions
  python3.1/site-packages/isc/{cc,config}
sbin/
  bind10
share/
  share/bind10/
    auth.spec
    b10-cmdctl.pem
    init.spec
    passwd.csv
  man/
var/
  bind10/b10-config.db
-->

    <para>
      BIND 10 also provides libraries and programmer interfaces
      for C++ and Python for the message bus and configuration backend,
      and, of course, DHCP. These include detailed developer
      documentation and code examples.
<!-- TODO point to this -->
    </para>

  </chapter>
