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<!--
     The FreeBSD Documentation Project

     $FreeBSD$
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<chapter xmlns="http://docbook.org/ns/docbook"
  xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0"
  xml:id="introduction">

  <info>
    <title>Introduction</title>

    <authorgroup>
      <author>
	<personname>
	  <firstname>Jim</firstname>
	  <surname>Mock</surname>
	</personname>
	<contrib>Restructured, reorganized, and parts rewritten
	  by </contrib>
      </author>
    </authorgroup>
  </info>

  <sect1 xml:id="introduction-synopsis">
    <title>Synopsis</title>

    <para>Thank you for your interest in &os;!  The following chapter
      covers various aspects of the &os;&nbsp;Project, such as its
      history, goals, development model, and so on.</para>

    <para>After reading this chapter, you will know:</para>

    <itemizedlist>
      <listitem>
	<para>How &os; relates to other computer operating
	  systems.</para>
      </listitem>

      <listitem>
	<para>The history of the &os;&nbsp;Project.</para>
      </listitem>

      <listitem>
	<para>The goals of the &os;&nbsp;Project.</para>
      </listitem>

      <listitem>
	<para>The basics of the &os; open-source development
	  model.</para>
      </listitem>

      <listitem>
	<para>And of course: where the name <quote>&os;</quote> comes
	  from.</para>
      </listitem>
    </itemizedlist>
  </sect1>

  <sect1 xml:id="nutshell">
    <title>Welcome to &os;!</title>

    <indexterm><primary>4.4BSD-Lite</primary></indexterm>

    <para>&os; is an Open Source, Unix-like operating system for x86
      (both 32 and 64 bit), &arm;, AArch64, &risc-v;, &mips;, &power;,
      &powerpc;, and Sun &ultrasparc; computers, originally based
      on 4.4BSD-Lite.  You can also read about
      <link linkend="history">the history of &os;</link>, or the
      <link xlink:href="&url.base;/releases">current release</link>.
      If you are interested in contributing something to the Project
      (code, hardware, funding), see the <link
	xlink:href="&url.articles.contributing;/index.html">Contributing
	to &os;</link> article.</para>

    <sect2 xml:id="os-overview">
      <title>What Can &os; Do?</title>

      <para>&os; is a complete, Open Source, standards-compliant
	Unix system, with all the associated features that are
	nowadays taken for granted, such as preemptive multitasking,
	memory protection, virtual memory, multi-user facilities, SMP
	support, all the Open Source development tools for different
	languages and frameworks, and desktop features centered around
	X Window System, KDE, or GNOME.  Its particular strenghts
	are:</para>

      <itemizedlist>
	<listitem>
	  <para><emphasis>Liberal Open Source license</emphasis>,
	    which grants you rights to freely modify and extend
	    its source code and incorporate it in both Open Source
	    projects and closed products without imposing
	    restrictions typical to copyleft licenses, as well
	    as avoiding potential license incompatibility
	    problems.</para>
	</listitem>

	<listitem>
	  <para><emphasis>Strong TCP/IP networking</emphasis>
	    <indexterm> <primary>TCP/IP
		networking</primary></indexterm> - &os;
	    implements industry standard protocols with ever
	    increasing performance and scalability.  This makes
	    it a good match in both server, and routing/firewalling
	    roles - and indeed many companies and vendors use it
	    precisely for that purpose.</para>
	</listitem>

	<listitem>
	  <para><emphasis>Fully integrated OpenZFS support</emphasis>,
	    including root-on-ZFS, ZFS Boot Environments, fault
	    management, administrative delegation, support for jails,
	    &os; specific documentation, and system installer
	    support.</para>
	</listitem>

	<listitem>
	  <para><emphasis>Extensive security features</emphasis>,
	    from the Mandatory Access Control framework to Capsicum
	    capability and sandbox mechanisms.</para>
	</listitem>

	<listitem>
	  <para><emphasis>Over 30 thousand prebuilt
	      packages</emphasis> for all supported architectures,
	    and the Ports Collection which makes it easy to build your
	    own, customized ones.</para>
	</listitem>

	<listitem>
	  <para><emphasis>Documentation</emphasis> - in addition
	    to Handbook and books from different authors that cover
	    topics ranging from system administration to kernel
	    internals, there are also the &man.man.1; pages, not only
	    for userspace daemons, utilities, and configuration files,
	    but also for kernel driver APIs (section 9) and individual
	    drivers (section 4).</para>
	</listitem>

	<listitem>
	  <para><emphasis>Simple and consistent repository structure
	      and build system</emphasis> - &os; uses a single
	    repository for all of its components, both kernel and
	    userspace.  This, along with an unified and easy to
	    customize build system and a well thought out development
	    process makes it easy to integrate &os; with build
	    infrastructure for your own product.</para>
	</listitem>

	<listitem>
	  <para><emphasis>Staying true to Unix philosophy</emphasis>,
	    preferring composability instead of monolithic <quote>all
	      in one</quote> daemons with hardcoded behaviour.</para>
	</listitem>

	<listitem>
	  <para><indexterm> <primary>binary compatibility</primary>
	      <secondary>Linux</secondary></indexterm>
	    <emphasis>Binary compatibility</emphasis> with Linux,
	    which makes it possible to run many Linux binaries without
	    the need for virtualisation.</para>
	</listitem>
      </itemizedlist>

      <para>&os; is based on the 4.4BSD-Lite<indexterm>
	  <primary>4.4BSD-Lite</primary>
	</indexterm> release from Computer
	Systems Research Group (CSRG)<indexterm>
	  <primary>Computer Systems Research Group (CSRG)</primary>
	</indexterm> at the University of California at Berkeley, and
	carries on the distinguished tradition of BSD systems
	development.  In addition to the fine work provided by CSRG,
	the &os;&nbsp;Project has put in many thousands of man-hours
	into extending the functionality and fine-tuning the system
	for maximum performance and reliability
	in real-life load situations.  &os; offers performance and
	reliability on par with other Open Source and commercial
	offerings, combined with cutting-edge features not available
	anywhere else.</para>

      <para>The applications to which &os; can be put are truly
	limited only by your own imagination.  From software
	development to factory automation, inventory control to
	azimuth correction of remote satellite antennae; if it can be
	done with a commercial &unix; product then it is more than
	likely that you can do it with &os; too!  &os; also benefits
	significantly from literally thousands of high quality
	applications developed by research centers and universities
	around the world, often available at little to no cost.</para>

      <para>Because the source code for &os; itself is generally
	available, the system can also be customized to an almost
	unheard of degree for special applications or projects, and in
	ways not generally possible with operating systems from most
	major commercial vendors.  Here is just a sampling of some of
	the applications in which people are currently using
	&os;:</para>

      <itemizedlist>
	<listitem>
	  <para><emphasis>Internet Services:</emphasis> The robust
	    TCP/IP networking built into &os; makes it an ideal
	    platform for a variety of Internet services such
	    as:</para>

	  <itemizedlist>
	    <listitem>
	      <para>World Wide Web servers<indexterm>
		  <primary>web servers</primary>
		</indexterm>
		(standard or secure [SSL])</para>
	    </listitem>

	    <listitem>
	      <para>IPv4 and IPv6 routing</para>
	    </listitem>

	    <listitem>
	      <para>Firewalls<indexterm>
		  <primary>firewall</primary>
		</indexterm>
		and NAT<indexterm>
		  <primary>NAT</primary>
		</indexterm>
		(<quote>IP masquerading</quote>) gateways</para>
	    </listitem>

	    <listitem>
	      <para>FTP servers<indexterm>
		  <primary>FTP servers</primary>
		</indexterm></para>
	    </listitem>

	    <listitem>
	      <para>
		<indexterm>
		  <primary>electronic mail</primary>
		  <see>email</see>
		</indexterm>
		<indexterm>
		  <primary>email</primary>
		</indexterm>
		Electronic Mail servers</para>
	    </listitem>

	    <listitem>
	      <para>And more...</para>
	    </listitem>
	  </itemizedlist>
	</listitem>

	<listitem>
	  <para><emphasis>Education:</emphasis>  Are you a student of
	    computer science or a related engineering field?  There
	    is no better way of learning about operating systems,
	    computer architecture and networking than the hands on,
	    under the hood experience that &os; can provide.  A number
	    of freely available CAD, mathematical and graphic design
	    packages also make it highly useful to those whose primary
	    interest in a computer is to get
	    <emphasis>other</emphasis> work done!</para>
	</listitem>

	<listitem>
	  <para><emphasis>Research:</emphasis>  With source code for
	    the entire system available, &os; is an excellent platform
	    for research in operating systems as well as other
	    branches of computer science.  &os;'s freely available
	    nature also makes it possible for remote groups to
	    collaborate on ideas or shared development without having
	    to worry about special licensing agreements or limitations
	    on what may be discussed in open forums.</para>
	</listitem>

	<listitem>
	  <para><emphasis>Networking:</emphasis> Need a new
	    router?<indexterm>
	      <primary>router</primary>
	    </indexterm>  A name server (DNS)?<indexterm>
	      <primary>DNS Server</primary>
	    </indexterm>  A firewall to keep people out of your
	    internal network?  &os; can easily turn that unused
	    PC sitting in the corner into an advanced router with
	    sophisticated packet-filtering capabilities.</para>
	</listitem>

	<listitem>
	  <para><emphasis>Embedded:</emphasis> &os; makes an
	    excellent platform to build embedded systems upon.
	    <indexterm>
	      <primary>embedded</primary>
	    </indexterm>
	    With support for the &arm;, &mips; and &powerpc;
	    platforms, coupled with a robust network stack, cutting
	    edge features and the permissive <link
	      xlink:href="&url.books.faq;/introduction.html#bsd-license-restrictions">BSD
	      license</link> &os; makes an excellent foundation for
	    building embedded routers, firewalls, and other
	    devices.</para>
	</listitem>

	<listitem>
	  <para>
	    <indexterm>
	      <primary>X Window System</primary>
	    </indexterm>
	    <indexterm>
	      <primary>GNOME</primary>
	    </indexterm>
	    <indexterm>
	      <primary>KDE</primary>
	    </indexterm>
	    <emphasis>Desktop:</emphasis> &os; makes a
	    fine choice for an inexpensive desktop solution
	    using the freely available X11 server.
	    &os; offers a choice from many open-source desktop
	    environments, including the standard
	    <application>GNOME</application> and
	    <application>KDE</application> graphical user interfaces.
	    &os; can even boot <quote>diskless</quote> from
	    a central server, making individual workstations
	    even cheaper and easier to administer.</para>
	</listitem>

	<listitem>
	  <para><emphasis>Software Development:</emphasis>  The basic
	    &os; system comes with a full complement of development
	    tools including a full
	    C/C++<indexterm>
	      <primary>Compiler</primary>
	    </indexterm>
	    compiler and debugger suite.
	    Support for many other languages are also available
	    through the ports and packages collection.</para>
	</listitem>
      </itemizedlist>

      <para>&os; is available to download free of charge, or can be
	obtained on either CD-ROM or DVD.  Please see
	<xref linkend="mirrors"/> for more information about obtaining
	&os;.</para>
    </sect2>

    <sect2 xml:id="introduction-nutshell-users">
      <title>Who Uses &os;?</title>

      <indexterm>
	<primary>users</primary>
	<secondary>large sites running &os;</secondary>
      </indexterm>

      <para>&os;'s advanced features, proven security, predictable
	release cycle, and permissive license have led to its use as a
	platform for building many commercial and open source
	appliances, devices, and products.  Many of the world's
	largest IT companies use &os;:</para>

      <itemizedlist>
	<listitem>

	  <para><link
	      xlink:href="http://www.apache.org/">Apache</link>
	    <indexterm>
	      <primary>Apache</primary>
	    </indexterm> - The Apache Software Foundation runs most of
	    its public facing infrastructure, including possibly one
	    of the largest SVN repositories in the world with over 1.4
	    million commits, on &os;.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.apple.com/">Apple</link>
	    <indexterm>
	      <primary>Apple</primary>
	    </indexterm> - OS X borrows heavily from &os; for the
	    network stack, virtual file system, and many userland
	    components.  Apple iOS also contains elements borrowed
	    from &os;.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.cisco.com/">Cisco</link>
	    <indexterm>
	      <primary>Cisco</primary>
	    </indexterm> - IronPort network security and anti-spam
	    appliances run a modified &os; kernel.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.citrix.com/">Citrix</link>
	    <indexterm>
	      <primary>Citrix</primary>
	    </indexterm> - The NetScaler line of security appliances
	    provide layer 4-7 load balancing, content caching,
	    application firewall, secure VPN, and mobile cloud network
	    access, along with the power of a &os; shell.</para>
	</listitem>

	<listitem>
	  <para><link xlink:href="http://www.dell.com/KACE">Dell
	      KACE</link>
	    <indexterm>
	      <primary>Dell KACE</primary>
	    </indexterm> - The KACE system management appliances run
	    &os; because of its reliability, scalability, and the
	    community that supports its continued development.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.experts-exchange.com/">Experts
	      Exchange</link>
	    <indexterm>
	      <primary>Experts Exchange</primary>
	    </indexterm> - All public facing web servers are powered
	    by &os; and they make extensive use of jails to isolate
	    development and testing environments without the overhead
	    of virtualization.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.isilon.com/">Isilon</link>
	    <indexterm>
	      <primary>Isilon</primary>
	    </indexterm> - Isilon's enterprise storage appliances
	    are based on &os;.  The extremely liberal &os; license
	    allowed Isilon to integrate their intellectual property
	    throughout the kernel and focus on building their product
	    instead of an operating system.</para>

	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.ixsystems.com/">iXsystems</link>
	    <indexterm>
	      <primary>iXsystems</primary>
	    </indexterm> - The TrueNAS line of unified storage
	    appliances is based on &os;.  In addition to their
	    commercial products, iXsystems also manages development of
	    the open source projects TrueOS and FreeNAS.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.juniper.net/">Juniper</link>
	    <indexterm>
	      <primary>Juniper</primary>
	    </indexterm> - The JunOS operating system that powers all
	    Juniper networking gear (including routers, switches,
	    security, and networking appliances) is based on &os;.
	    Juniper is one of many vendors that showcases the
	    symbiotic relationship between the project and vendors of
	    commercial products.  Improvements generated at Juniper
	    are upstreamed into &os; to reduce the complexity of
	    integrating new features from &os; back into JunOS in the
	    future.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.mcafee.com/">McAfee</link>
	    <indexterm>
	      <primary>McAfee</primary>
	    </indexterm> - SecurOS, the basis of McAfee enterprise
	    firewall products including Sidewinder is based on
	    &os;.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.netapp.com/">NetApp</link>
	    <indexterm>
	      <primary>NetApp</primary>
	    </indexterm> - The Data ONTAP GX line of storage
	    appliances are based on &os;.  In addition, NetApp has
	    contributed back many features, including the new BSD
	    licensed hypervisor, bhyve.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.netflix.com/">Netflix</link>
	    <indexterm>
	      <primary>Netflix</primary>
	    </indexterm> - The OpenConnect appliance that Netflix
	    uses to stream movies to its customers is based on &os;.
	    Netflix has made extensive contributions to the codebase
	    and works to maintain a zero delta from mainline &os;.
	    Netflix OpenConnect appliances are responsible for
	    delivering more than 32% of all Internet traffic in North
	    America.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.sandvine.com/">Sandvine</link>
	    <indexterm>
	      <primary>Sandvine</primary>
	    </indexterm> - Sandvine uses &os; as the basis of their
	    high performance real-time network processing platforms
	    that make up their intelligent network policy control
	    products.</para>
	</listitem>

	<listitem>
	  <para><link xlink:href="http://www.sony.com/">Sony</link>
	    <indexterm>
	      <primary>Sony</primary>
	    </indexterm> - The PlayStation 4 gaming console runs a
	    modified version of &os;.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.sophos.com/">Sophos</link>
	    <indexterm>
	      <primary>Sophos</primary>
	    </indexterm> - The Sophos Email Appliance product is based
	    on a hardened &os; and scans inbound mail for spam and
	    viruses, while also monitoring outbound mail for malware
	    as well as the accidental loss of sensitive
	    information.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.spectralogic.com/">Spectra
	      Logic</link>
	    <indexterm>
	      <primary>Spectra Logic</primary>
	    </indexterm> - The nTier line of archive grade storage
	    appliances run &os; and OpenZFS.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="https://www.stormshield.eu">Stormshield</link>
	    <indexterm>
	      <primary>Stormshield</primary>

	    </indexterm> - Stormshield Network Security appliances
	    are based on a hardened version of &os;.  The BSD license
	    allows them to integrate their own intellectual property with
	    the system while returning a great deal of interesting
	    development to the community.</para>
	</listitem>

	<listitem>
	  <para><link xlink:href="http://www.weather.com/">The Weather
	      Channel</link>
	    <indexterm>
	      <primary>The Weather Channel</primary>

	    </indexterm> - The IntelliStar appliance that is installed
	    at each local cable provider's headend and is responsible
	    for injecting local weather forecasts into the cable TV
	    network's programming runs &os;.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.verisign.com/">Verisign</link>
	    <indexterm>
	      <primary>Verisign</primary>

	    </indexterm> - Verisign is responsible for operating the
	    .com and .net root domain registries as well as the
	    accompanying DNS infrastructure.  They rely on a number of
	    different network operating systems including &os; to
	    ensure there is no common point of failure in their
	    infrastructure.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.voxer.com/">Voxer</link>
	    <indexterm>
	      <primary>Voxer</primary>

	    </indexterm> - Voxer powers their mobile voice messaging
	    platform with ZFS on &os;.  Voxer switched from a Solaris
	    derivative to &os; because of its superior documentation,
	    larger and more active community, and more developer
	    friendly environment.  In addition to critical features
	    like <acronym>ZFS</acronym> and DTrace, &os; also offers
	    TRIM support for <acronym>ZFS</acronym>.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.whatsapp.com/">WhatsApp</link>
	    <indexterm>
	      <primary>WhatsApp</primary>
	    </indexterm> - When WhatsApp needed a platform that would
	    be able to handle more than 1 million concurrent TCP
	    connections per server, they chose &os;.  They then
	    proceeded to scale past 2.5 million connections per
	    server.</para>
	</listitem>

	<listitem>
	  <para><link xlink:href="http://wheelsystems.com/">Wheel
	      Systems</link>
	    <indexterm>
	      <primary>Wheel Systems</primary>

	    </indexterm> - The FUDO security appliance allows
	    enterprises to monitor, control, record, and audit
	    contractors and administrators who work on their systems.
	    Based on all of the best security features of &os;
	    including ZFS, GELI, Capsicum, HAST, and
	    auditdistd.</para>
	</listitem>
      </itemizedlist>

      <para>&os; has also spawned a number of related open source
	projects:</para>

      <itemizedlist>
	<listitem>
	  <para><link xlink:href="http://bsdrp.net/">BSD
	      Router</link>
	    <indexterm>
	      <primary>BSD Router</primary>
	    </indexterm> - A &os; based replacement for large
	    enterprise routers designed to run on standard PC
	    hardware.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.freenas.org/">FreeNAS</link>
	    <indexterm>
	      <primary>FreeNAS</primary>
	    </indexterm> - A customized &os; designed to be used as a
	    network file server appliance.  Provides a python based
	    web interface to simplify the management of both the UFS
	    and ZFS file systems.  Includes support for NFS, SMB/CIFS,
	    AFP, FTP, and iSCSI.  Includes an extensible plugin system
	    based on &os; jails.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.ghostbsd.org/">GhostBSD</link>
	    <indexterm>
	      <primary>GhostBSD</primary>
	    </indexterm> - A desktop oriented distribution of &os;
	    bundled with the Gnome desktop environment.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://mfsbsd.vx.sk/">mfsBSD</link>
	    <indexterm>
	      <primary>mfsBSD</primary>
	    </indexterm> - A toolkit for building a &os; system image
	    that runs entirely from memory.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.nas4free.org/">NAS4Free</link>
	    <indexterm>
	      <primary>NAS4Free</primary>
	    </indexterm> - A file server distribution based on &os;
	    with a PHP powered web interface.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.opnsense.org/">OPNSense</link>
	    <indexterm>
	      <primary>OPNsense</primary>
	    </indexterm> - OPNsense is an open source, easy-to-use and
	    easy-to-build FreeBSD based firewall and routing platform.
	    OPNsense includes most of the features available in
	    expensive commercial firewalls, and more in many cases.
	    It brings the rich feature set of commercial offerings
	    with the benefits of open and verifiable sources.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="https://www.trueos.org">TrueOS</link>
	    <indexterm>
	      <primary>TrueOS</primary>
	    </indexterm> - A customized version of &os; geared towards
	    desktop users with graphical utilities to exposing the
	    power of &os; to all users.  Designed to ease the
	    transition of Windows and OS X users.</para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.pfsense.org/">pfSense</link>
	    <indexterm>
	      <primary>pfSense</primary>
	    </indexterm> - A firewall distribution based on &os; with
	    a huge array of features and extensive IPv6
	    support.</para>
	</listitem>

	<listitem>
	  <para><link xlink:href="http://zrouter.org/">ZRouter</link>
	    <indexterm>
	      <primary>ZRouter</primary>
	    </indexterm> - An open source alternative firmware for
	    embedded devices based on &os;.  Designed to replace the
	    proprietary firmware on off-the-shelf routers.</para>
	</listitem>
      </itemizedlist>

      <para>&os; is also used to power some of the biggest sites on
	the Internet, including:</para>

      <itemizedlist>
	<listitem>
	  <para><link xlink:href="http://www.yahoo.com/">Yahoo!</link>
	    <indexterm>
	      <primary>Yahoo!</primary>
	    </indexterm></para>
	</listitem>

	<listitem>
	  <para><link xlink:href="http://www.yandex.ru/">Yandex</link>
	    <indexterm>
	      <primary>Yandex</primary>
	    </indexterm></para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.rambler.ru/">Rambler</link>
	    <indexterm>
	      <primary>Rambler</primary>
	    </indexterm></para>
	</listitem>

	<listitem>
	  <para><link xlink:href="http://www.sina.com/">Sina</link>
	    <indexterm>
	      <primary>Sina</primary>
	    </indexterm></para>
	</listitem>

	<listitem>
	  <para><link xlink:href="http://www.pair.com/">Pair
	      Networks</link>
	    <indexterm>
	      <primary>Pair Networks</primary>
	    </indexterm></para>
	</listitem>

	<listitem>
	  <para><link xlink:href="http://www.sony.co.jp/">Sony
	      Japan</link>
	    <indexterm>
	      <primary>Sony Japan</primary>
	    </indexterm></para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.netcraft.com/">Netcraft</link>
	    <indexterm>
	      <primary>Netcraft</primary>
	    </indexterm></para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="https://signup.netflix.com/openconnect">Netflix</link>
	    <indexterm>
	      <primary>Netflix</primary>
	    </indexterm></para>
	</listitem>

	<listitem>
	  <para><link xlink:href="http://www.163.com/">NetEase</link>
	    <indexterm>
	      <primary>NetEase</primary>
	    </indexterm></para>
	</listitem>

	<listitem>
	  <para><link
	      xlink:href="http://www.weathernews.com/">Weathernews</link>
	    <indexterm>
	      <primary>Weathernews</primary>
	    </indexterm></para>
	</listitem>

	<listitem>
	  <para><link xlink:href="http://www.telehouse.com/">TELEHOUSE
	      America</link>
	    <indexterm>
	      <primary>TELEHOUSE America</primary>
	    </indexterm></para>
	</listitem>

      </itemizedlist>

      <para>and many more.  Wikipedia also maintains a <link
	  xlink:href="http://en.wikipedia.org/wiki/List_of_products_based_on_FreeBSD">list
	  of products based on &os;</link>.</para>
    </sect2>
  </sect1>

  <sect1 xml:id="history">
    <title>About the &os;&nbsp;Project</title>

    <para>The following section provides some background information
      on the project, including a brief history, project goals, and
      the development model of the project.</para>

    <sect2 xml:id="intro-history">
      <title>A Brief History of &os;</title>

      <indexterm><primary>386BSD Patchkit</primary></indexterm>
      <indexterm><primary>Hubbard, Jordan</primary></indexterm>
      <indexterm><primary>Williams, Nate</primary></indexterm>
      <indexterm><primary>Grimes, Rod</primary></indexterm>
      <indexterm>
	<primary>FreeBSD Project</primary>
	<secondary>history</secondary>
      </indexterm>

      <para>The &os;&nbsp;Project had its genesis in the early part
	of 1993, partially as an outgrowth of the Unofficial
	386BSDPatchkit by the patchkit's last 3 coordinators: Nate
	Williams, Rod Grimes and Jordan Hubbard.</para>

      <indexterm><primary>386BSD</primary></indexterm>
      <para>The original goal was to produce an intermediate snapshot
	of 386BSD in order to fix a number of problems with it that
	the patchkit mechanism just was not capable of solving.  The
	early working title for the project was 386BSD 0.5 or 386BSD
	Interim in reference of that fact.</para>

      <indexterm><primary>Jolitz, Bill</primary></indexterm>
      <para>386BSD was Bill Jolitz's operating system, which had been
	up to that point suffering rather severely from almost a
	year's worth of neglect.  As the patchkit swelled ever more
	uncomfortably with each passing day, they decided to assist
	Bill by providing this interim <quote>cleanup</quote>
	snapshot.  Those plans came to a rude halt when Bill Jolitz
	suddenly decided to withdraw his sanction from the project
	without any clear indication of what would be done
	instead.</para>

      <indexterm><primary>Greenman, David</primary></indexterm>
      <indexterm><primary>Walnut Creek CDROM</primary></indexterm>

      <para>The trio thought that the goal remained worthwhile, even
	without Bill's support, and so they adopted the name "&os;"
	coined by David Greenman.  The initial objectives were set
	after consulting with the system's current users and, once it
	became clear that the project was on the road to perhaps even
	becoming a reality, Jordan contacted Walnut Creek CDROM with
	an eye toward improving &os;'s distribution channels for those
	many unfortunates without easy access to the Internet.  Walnut
	Creek CDROM not only supported the idea of distributing &os;
	on CD but also went so far as to provide the project with a
	machine to work on and a fast Internet connection.  Without
	Walnut Creek CDROM's almost unprecedented degree of faith in
	what was, at the time, a completely unknown project, it is
	quite unlikely that &os; would have gotten as far, as fast, as
	it has today.</para>

      <indexterm><primary>4.3BSD-Lite</primary></indexterm>
      <indexterm><primary>Net/2</primary></indexterm>
      <indexterm><primary>U.C. Berkeley</primary></indexterm>
      <indexterm><primary>386BSD</primary></indexterm>
      <indexterm><primary>Free Software
	  Foundation</primary></indexterm>
      <para>The first CD-ROM (and general net-wide) distribution was
	&os;&nbsp;1.0, released in December of 1993.  This was based
	on the 4.3BSD-Lite (<quote>Net/2</quote>) tape from U.C.
	Berkeley, with many components also provided by 386BSD and the
	Free Software Foundation.  It was a fairly reasonable success
	for a first offering, and they followed it with the highly
	successful &os; 1.1 release in May of 1994.</para>

      <indexterm><primary>Novell</primary></indexterm>
      <indexterm><primary>U.C. Berkeley</primary></indexterm>
      <indexterm><primary>Net/2</primary></indexterm>
      <indexterm><primary>AT&amp;T</primary></indexterm>
      <para>Around this time, some rather unexpected storm clouds
	formed on the horizon as Novell and U.C. Berkeley settled
	their long-running lawsuit over the legal status of the
	Berkeley Net/2 tape.  A condition of that settlement was U.C.
	Berkeley's concession that large parts of Net/2 were
	<quote>encumbered</quote> code and the property of Novell, who
	had in turn acquired it from AT&amp;T some time previously.
	What Berkeley got in return was Novell's
	<quote>blessing</quote> that the 4.4BSD-Lite release, when
	it was finally released, would be declared unencumbered and
	all existing Net/2 users would be strongly encouraged to
	switch.  This included &os;, and the project was given until
	the end of July 1994 to stop shipping its own Net/2 based
	product.  Under the terms of that agreement, the project was
	allowed one last release before the deadline, that release
	being &os;&nbsp;1.1.5.1.</para>

      <para>&os; then set about the arduous task of literally
	re-inventing itself from a completely new and rather
	incomplete set of 4.4BSD-Lite bits.  The <quote>Lite</quote>
	releases were light in part because Berkeley's CSRG had
	removed large chunks of code required for actually
	constructing a bootable running system (due to various legal
	requirements) and the fact that the Intel port of 4.4 was
	highly incomplete.  It took the project until November of 1994
	to make this transition, and in December it released
	&os;&nbsp;2.0 to the world.  Despite being still more than a
	little rough around the edges, the release was a significant
	success and was followed by the more robust and easier to
	install &os;&nbsp;2.0.5 release in June of 1995.</para>

      <para>Since that time, &os; has made a series of releases each
	time improving the stability, speed, and feature set of the
	previous version.</para>

      <para>For now, long-term development projects continue to take
	place in the 10.X-CURRENT (trunk) branch, and snapshot
	releases of 10.X are continually made available from <link
	  xlink:href="ftp://ftp.FreeBSD.org/pub/FreeBSD/snapshots/">the
	  snapshot server</link> as work progresses.</para>
    </sect2>

    <sect2 xml:id="goals">
      <info>
	<title>&os;&nbsp;Project Goals</title>

	<authorgroup>
	  <author>
	    <personname>
	      <firstname>Jordan</firstname>
	      <surname>Hubbard</surname>
	    </personname>
	    <contrib>Contributed by </contrib>
	  </author>
	</authorgroup>
      </info>

      <indexterm>
	<primary>FreeBSD Project</primary>
	<secondary>goals</secondary>
      </indexterm>
      <para>The goals of the &os;&nbsp;Project are to provide software
	that may be used for any purpose and without strings attached.
	Many of us have a significant investment in the code (and
	project) and would certainly not mind a little financial
	compensation now and then, but we are definitely not prepared
	to insist on it.  We believe that our first and foremost
	<quote>mission</quote> is to provide code to any and all
	comers, and for whatever purpose, so that the code gets the
	widest possible use and provides the widest possible benefit.
	This is, I believe, one of the most fundamental goals of Free
	Software and one that we enthusiastically support.</para>

      <indexterm>
	<primary>GNU General Public License (GPL)</primary>
      </indexterm>
      <indexterm>
	<primary>GNU Lesser General Public License (LGPL)</primary>
      </indexterm>
      <indexterm><primary>BSD Copyright</primary></indexterm>
      <para>That code in our source tree which falls under the GNU
	General Public License (GPL) or Library General Public License
	(LGPL) comes with slightly more strings attached, though at
	least on the side of enforced access rather than the usual
	opposite.  Due to the additional complexities that can evolve
	in the commercial use of GPL software we do, however, prefer
	software submitted under the more relaxed BSD copyright when
	it is a reasonable option to do so.</para>
    </sect2>

    <sect2 xml:id="development">
      <info>
	<title>The &os; Development Model</title>

	<authorgroup>
	  <author>
	    <personname>
	      <firstname>Satoshi</firstname>
	      <surname>Asami</surname>
	    </personname>
	    <contrib>Contributed by </contrib>
	  </author>
	</authorgroup>
      </info>

      <indexterm>
	<primary>FreeBSD Project</primary>
	<secondary>development model</secondary>
      </indexterm>

      <para>The development of &os; is a very open and flexible
	process, being literally built from the contributions of
	thousands of people around the world, as can be seen from our
	<link
	  xlink:href="&url.articles.contributors;/article.html">list
	  of contributors</link>.  &os;'s development infrastructure
	allow these thousands of contributors to collaborate over the
	Internet.  We are constantly on the lookout for new developers
	and ideas, and those interested in becoming more closely
	involved with the project need simply contact us at the
	&a.hackers;.  The &a.announce; is also available to those
	wishing to make other &os; users aware of major areas of
	work.</para>

      <para>Useful things to know about the &os;&nbsp;Project and its
	development process, whether working independently or in close
	cooperation:</para>

      <variablelist>
	<varlistentry>
	  <term>The SVN repositories<anchor
	    xml:id="development-cvs-repository"/></term>

	  <listitem>
	    <para>
	      <indexterm>
		<primary>CVS</primary>
	      </indexterm>

	      <indexterm>
		<primary>CVS Repository</primary>
	      </indexterm>

	      <indexterm>
		<primary>Concurrent Versions System</primary>
		<see>CVS</see>
	      </indexterm>

	      <indexterm>
		<primary>Subversion</primary>
	      </indexterm>

	      <indexterm>
		<primary>Subversion Repository</primary>
	      </indexterm>

	      <indexterm>
		<primary>SVN</primary>
		<see>Subversion</see>
	      </indexterm>
	      For several years, the central source tree for &os;
	      was maintained by
	      <link xlink:href="http://www.nongnu.org/cvs/">CVS</link>
	      (Concurrent Versions System), a freely available source
	      code control tool.  In June 2008, the Project switched
	      to using <link
		xlink:href="http://subversion.tigris.org">SVN</link>
	      (Subversion).  The switch was deemed necessary, as the
	      technical limitations imposed by
	      <application>CVS</application> were becoming obvious due
	      to the rapid expansion of the source tree and the amount
	      of history already stored.  The Documentation Project
	      and Ports Collection repositories also moved from
	      <application>CVS</application> to
	      <application>SVN</application> in May 2012 and July
	      2012, respectively.  Please refer to the <link
		linkend="synching">Synchronizing your source
		tree</link> section for more information on obtaining
	      the &os; <literal>src/</literal> repository and <link
		linkend="ports-using">Using the Ports
		Collection</link> for details on obtaining the &os;
	      Ports Collection.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>The committers list<anchor
	    xml:id="development-committers"/></term>

	  <listitem>
	    <para>The <firstterm>committers</firstterm>
	      <indexterm>
		<primary>committers</primary>
	      </indexterm> are the people who have
	      <emphasis>write</emphasis> access to the Subversion
	      tree, and are authorized to make modifications to the
	      &os; source (the term <quote>committer</quote> comes
	      from <command>commit</command>, the source control
	      command which is used to bring new changes into the
	      repository).  Anyone can submit a bug to the <link
		xlink:href="https://bugs.FreeBSD.org/submit/">Bug
	      Database</link>.  Before submitting a bug report, the
	    &os; mailing lists, IRC channels, or forums can be used to
	    help verify that an issue is actually a bug.</para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>The FreeBSD core team<anchor
	    xml:id="development-core"/></term>

	  <listitem>
	    <para>The <firstterm>&os; core team</firstterm>
	      <indexterm>
		<primary>core team</primary>
	      </indexterm> would be equivalent to the board of
	      directors if the &os;&nbsp;Project were a company.  The
	      primary task of the core team is to make sure the
	      project, as a whole, is in good shape and is heading in
	      the right directions.  Inviting dedicated and
	      responsible developers to join our group of committers
	      is one of the functions of the core team, as is the
	      recruitment of new core team members as others move on.
	      The current core team was elected from a pool of
	      committer candidates in July 2014.  Elections are held
	      every 2 years.</para>

	    <note>
	      <para>Like most developers, most members of the
		core team are also volunteers when
		it comes to &os; development and do not benefit from
		the project financially, so <quote>commitment</quote>
		should also not be misconstrued as meaning
		<quote>guaranteed support.</quote>  The
		<quote>board of directors</quote> analogy above is not
		very accurate, and it may be more suitable to say that
		these are the people who gave up their lives in favor
		of &os; against their better judgement!</para>
	    </note>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>Outside contributors</term>

	  <listitem>
	    <para>Last, but definitely not least, the largest group of
	      developers are the users themselves who provide feedback
	      and bug fixes to us on an almost constant basis.  The
	      primary way of keeping in touch with &os;'s more
	      non-centralized development is to subscribe to the
	      &a.hackers; where such things are discussed.  See
	      <xref linkend="eresources"/> for more information about
	      the various &os; mailing lists.</para>

	    <para><citetitle><link
		  xlink:href="&url.articles.contributors;/article.html">The
		  &os; Contributors List</link></citetitle>
	      <indexterm>
		<primary>contributors</primary>
	      </indexterm> is a long and growing one, so why not join
	      it by contributing something back to &os; today?</para>

	    <para>Providing code is not the only way of contributing
	      to the project; for a more complete list of things that
	      need doing, please refer to the <link
		xlink:href="&url.base;/index.html">&os;&nbsp;Project
		web site</link>.</para>
	  </listitem>
	</varlistentry>
      </variablelist>

      <para>In summary, our development model is organized as a loose
	set of concentric circles.  The centralized model is designed
	for the convenience of the <emphasis>users</emphasis> of &os;,
	who are provided with an easy way of tracking one central code
	base, not to keep potential contributors out! Our desire is to
	present a stable operating system with a large set of coherent
	<link linkend="ports">application programs</link> that the
	users can easily install and use &mdash; this model works very
	well in accomplishing that.</para>

      <para>All we ask of those who would join us as &os; developers
	is some of the same dedication its current people have to its
	continued success!</para>
    </sect2>

    <sect2 xml:id="third-party-programs">
      <title>Third Party Programs</title>

      <para>In addition to the base distributions, &os; offers a
	ported software collection with thousands of commonly
	sought-after programs.  At the time of this writing, there
	were over &os.numports; ports!  The list of ports ranges from
	http servers, to games, languages, editors, and almost
	everything in between.  The entire Ports Collection requires
	approximately &ports.size;.  To compile a port, you simply
	change to the directory of the program you wish to install,
	type <command>make install</command>, and let the system do
	the rest.  The full original distribution for each port you
	build is retrieved dynamically so you need only enough disk
	space to build the ports you want.  Almost every port is also
	provided as a pre-compiled <quote>package</quote>, which can
	be installed with a simple command
	(<command>pkg install</command>) by those who do not wish to
	compile their own ports from source.  More information on
	packages and ports can be found in
	<xref linkend="ports"/>.</para>
    </sect2>

    <sect2>
      <title>Additional Documentation</title>

      <para>All supported &os; versions provide an option in the
	installer to
	install additional documentation under
	<filename>/usr/local/share/doc/freebsd</filename> during the
	initial system setup.  Documentation may also be installed at
	any later time using packages as described in
	<xref linkend="doc-ports-install-package"/>.  You may view the
	locally installed manuals with any HTML capable browser using
	the following URLs:</para>

      <variablelist>
	<varlistentry>
	  <term>The FreeBSD Handbook</term>

	  <listitem>
	    <para><link
		xlink:href="file://localhost/usr/local/share/doc/freebsd/handbook/index.html"><filename>/usr/local/share/doc/freebsd/handbook/index.html</filename></link></para>
	  </listitem>
	</varlistentry>

	<varlistentry>
	  <term>The FreeBSD FAQ</term>

	  <listitem>
	    <para><link
		xlink:href="file://localhost/usr/local/share/doc/freebsd/faq/index.html"><filename>/usr/local/share/doc/freebsd/faq/index.html</filename></link></para>
	  </listitem>
	</varlistentry>
      </variablelist>

      <para>You can also view the master (and most frequently updated)
	copies at <uri
	  xlink:href="https://www.FreeBSD.org/">https://www.FreeBSD.org/</uri>.</para>
    </sect2>
  </sect1>
</chapter>