<!-- doc/src/sgml/start.sgml -->

 <chapter id="tutorial-start">
  <title>Getting Started</title>

  <sect1 id="tutorial-install">
   <title>Installation</title>

   <para>
    Before you can use <productname>PostgreSQL</productname> you need
    to install it, of course.  It is possible that
    <productname>PostgreSQL</productname> is already installed at your
    site, either because it was included in your operating system
    distribution or because the system administrator already installed
    it.  If that is the case, you should obtain information from the
    operating system documentation or your system administrator about
    how to access <productname>PostgreSQL</productname>.
   </para>

   <para>
    If you are not sure whether <productname>PostgreSQL</productname>
    is already available or whether you can use it for your
    experimentation then you can install it yourself.  Doing so is not
    hard and it can be a good exercise.
    <productname>PostgreSQL</productname> can be installed by any
    unprivileged user; no superuser (<systemitem>root</systemitem>)
    access is required.
   </para>

   <para>
    If you are installing <productname>PostgreSQL</productname>
    yourself, then refer to <xref linkend="installation"/>
    for instructions on installation, and return to
    this guide when the installation is complete.  Be sure to follow
    closely the section about setting up the appropriate environment
    variables.
   </para>

   <para>
    If your site administrator has not set things up in the default
    way, you might have some more work to do.  For example, if the
    database server machine is a remote machine, you will need to set
    the <envar>PGHOST</envar> environment variable to the name of the
    database server machine.  The environment variable
    <envar>PGPORT</envar> might also have to be set.  The bottom line is
    this: if you try to start an application program and it complains
    that it cannot connect to the database, you should consult your
    site administrator or, if that is you, the documentation to make
    sure that your environment is properly set up.  If you did not
    understand the preceding paragraph then read the next section.
   </para>
  </sect1>


  <sect1 id="tutorial-arch">
   <title>Architectural Fundamentals</title>

   <para>
    Before we proceed, you should understand the basic
    <productname>PostgreSQL</productname> system architecture.
    Understanding how the parts of
    <productname>PostgreSQL</productname> interact will make this
    chapter somewhat clearer.
   </para>

   <para>
    In database jargon, <productname>PostgreSQL</productname> uses a
    client/server model.  A <productname>PostgreSQL</productname>
    session consists of the following cooperating processes
    (programs):

    <itemizedlist>
     <listitem>
      <para>
       A server process, which manages the database files, accepts
       connections to the database from client applications, and
       performs database actions on behalf of the clients.  The
       database server program is called
       <filename>postgres</filename>.
       <indexterm><primary>postgres</primary></indexterm>
      </para>
     </listitem>

     <listitem>
      <para>
       The user's client (frontend) application that wants to perform
       database operations.  Client applications can be very diverse
       in nature:  a client could be a text-oriented tool, a graphical
       application, a web server that accesses the database to
       display web pages, or a specialized database maintenance tool.
       Some client applications are supplied with the
       <productname>PostgreSQL</productname> distribution; most are
       developed by users.
      </para>
     </listitem>

    </itemizedlist>
   </para>

   <para>
    As is typical of client/server applications, the client and the
    server can be on different hosts.  In that case they communicate
    over a TCP/IP network connection.