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<chapter id="web-servers" status="review">
    <title>Web Servers</title>
        <para>A Web server is a software responsible for accepting HTTP requests
    from clients, which are known as Web browsers, and serving them HTTP
    responses along with optional data contents, which usually are Web
    pages such as HTML documents and linked objects (images, etc.).</para>
    <sect1 id="httpd" status="review">
        <title>HTTPD - Apache2 Web Server</title>
      <para>Apache is the most commonly used Web Server on Linux systems. Web Servers are used
          to serve Web Pages requested by client computers. Clients typically request and view
          Web Pages using Web Browser applications such as <application>Firefox</application>,
              <application>Opera</application>, or <application>Mozilla</application>.</para>
      <para>Users enter a Uniform Resource Locator (URL) to point to a Web server by means of
          its Fully Qualified Domain Name (FQDN) and a path to the required resource. For example, to view the home page of
          the <ulink url="&ubuntu-web;">Ubuntu Web site</ulink> a user will enter only the FQDN. To request specific information about
              <ulink url="&ubuntu-paidsupport;">paid
              support</ulink>, a user will enter the FQDN followed by a path.</para>
      <para>The most common protocol used to transfer Web pages is the Hyper Text Transfer
          Protocol (HTTP). Protocols such as Hyper Text Transfer Protocol over Secure Sockets Layer (HTTPS), and
          File Transfer Protocol (FTP), a protocol for uploading and downloading files, are also
          supported.</para>
      <para>Apache Web Servers are often used in combination with the <application>MySQL</application>
          database engine, the HyperText Preprocessor (<application>PHP</application>)
          scripting language, and other popular scripting languages such as
              <application>Python</application> and <application>Perl</application>. This
          configuration is termed LAMP (Linux, Apache, MySQL and Perl/Python/PHP) and forms a
          powerful and robust platform for the development and deployment of Web-based
          applications.</para>
<sect2 id="http-installation" status="review">
  <title>Installation</title>
    <para>
    The Apache2 web server is available in Ubuntu Linux. To install Apache2:
    </para>

    <procedure>
      <step>
        <para>
        At a terminal prompt enter the following command:
        </para>

<screen>
<command>sudo apt-get install apache2</command>
</screen>

      </step>
    </procedure>

    </sect2>
    <sect2 id="http-configuration" status="review">
        <title>Configuration</title>

        <para>
        Apache2 is configured by placing <emphasis>directives</emphasis> in plain text
        configuration files.  The configuration files are separated between the following
        files and directories:
        </para>

        <itemizedlist>
          <listitem>
            <para>
            <emphasis>apache2.conf:</emphasis> the main Apache2 configuration file.  Contains settings that
            are <emphasis>global</emphasis> to Apache2.
            </para>
          </listitem>
          <listitem>
            <para>
            <emphasis>conf.d:</emphasis> contains configuration files which apply <emphasis>globally</emphasis> to Apache.
            Other packages that use Apache2 to serve content may add files, or symlinks, to this directory.
            </para>
          </listitem>
          <listitem>
            <para>
            <emphasis>envvars:</emphasis> file where Apache2 <emphasis>environment</emphasis> variables are set.
            </para>
          </listitem>
          <listitem>
            <para>
            <emphasis>httpd.conf:</emphasis> historically the main Apache2 configuration file, named after the
            <application>httpd</application> daemon.  The file can be used for <emphasis>user specific</emphasis>
            configuration options that globally effect Apache2.
            </para>
          </listitem>
          <listitem>
            <para>
            <emphasis>mods-available:</emphasis> this directory contains configuration files to both load
            <emphasis>modules</emphasis> and configure them.  Not all modules will have specific configuration files, however.
            </para>
          </listitem>
          <listitem>
            <para>
            <emphasis>mods-enabled:</emphasis> holds <emphasis>symlinks</emphasis> to the files in
            <filename>/etc/apache2/mods-available</filename>.  When a module configuration file is symlinked it will be enabled
            the next time <application>apache2</application> is restarted.
            </para>
          </listitem>
          <listitem>
            <para>
            <emphasis>ports.conf:</emphasis> houses the directives that determine which TCP ports Apache2 is listening on.
            </para>
          </listitem>
          <listitem>
            <para>
            <emphasis>sites-available:</emphasis> this directory has configuration files for Apache <emphasis>Virtual Hosts</emphasis>.
            Virtual Hosts allow Apache2 to be configured for multiple sites that have separate configurations.
            </para>
          </listitem>
          <listitem>
            <para>
            <emphasis>sites-enabled:</emphasis> like mods-enabled, <filename role='directory'>sites-enabled</filename> contains
            symlinks to the <filename>/etc/apache2/sites-available</filename> directory.  Similarly when a configuration file in
            sites-available is symlinked it will be active once Apache is restarted.
            </para>
          </listitem>
        </itemizedlist>

          <para>
          In addition, other configuration files may be added
          using the <emphasis>Include</emphasis> directive, and wildcards can be used to
          include many configuration files. Any directive may be placed
          in any of these configuration files. Changes to the main
          configuration files are only recognized by Apache2 when it is
          started or restarted.
          </para>

          <para>The server also reads a file containing mime document types;
          the filename is set by the <emphasis>TypesConfig</emphasis> directive, and is
          <filename>/etc/mime.types</filename> by default.</para>

        <sect3 id="http-basic-settings" status="review">
          <title>Basic Settings</title>
            <para>
             This section explains Apache2 server essential configuration
             parameters. Refer to the <ulink
             url="http://httpd.apache.org/docs/2.2/">Apache2
             Documentation</ulink> for more details.</para>

             <itemizedlist>
               <listitem>
                 <para>
                 Apache2 ships with a virtual-host-friendly default configuration.
             That is, it is configured with a single default virtual host (using
         the <emphasis>VirtualHost</emphasis> directive) which can modified or used as-is if you
         have a single site, or used as a template for additional virtual hosts
         if you have multiple sites.  If left alone, the default virtual host
         will serve as your default site, or the site users will see if the
         URL they enter does not match the <emphasis>ServerName</emphasis> directive of any of your
         custom sites.  To modify the default virtual host, edit the file
         <filename>/etc/apache2/sites-available/default</filename>.
                 </para>

                 <note>
                   <para>
                   The directives set for a virtual host only apply to that particular virtual host. If a
                   directive is set server-wide and not defined within the virtual host settings, the default
                   setting is used. For example, you can define a Webmaster email address and not define
                   individual email addresses for each virtual host.
                   </para>
                 </note>

                 <para>
                 If you wish to configure a new virtual host or site, copy that file into the
         same directory with a name you choose.  For example:
                 </para>

<screen>
<command>sudo cp /etc/apache2/sites-available/default /etc/apache2/sites-available/mynewsite</command>
</screen>

                 <para>
         Edit the new file to configure the new site using some of the directives
         described below.
                 </para>

               </listitem>
               <listitem>
                 <para>
         The <emphasis>ServerAdmin</emphasis> directive specifies the email address to be advertised
         for the server's administrator.  The default value is webmaster@localhost.
         This should be changed to an email address that is delivered to you (if you
         are the server's administrator).  If your website has a problem, Apache2
         will display an error message containing this email address to report the
         problem to.  Find this directive in your site's configuration file in
         /etc/apache2/sites-available.
         </para>
               </listitem>
               <listitem>
                 <para>
                 The <emphasis>Listen</emphasis> directive specifies the port, and optionally the IP address,
                 Apache2 should listen on. If the IP address is not specified, Apache2
             will listen on all IP addresses assigned to the machine it runs on.
             The default value for the Listen directive is 80.  Change this to
             127.0.0.1:80 to cause Apache2 to listen only on your loopback interface
             so that it will not be available to the Internet, to (for example) 81
                 to change the port that it listens on, or leave it as is for normal
                 operation.  This directive can be found and changed in its own file,
             <filename>/etc/apache2/ports.conf</filename>
                 </para>
               </listitem>
               <listitem>
                 <para>
             The <emphasis>ServerName</emphasis> directive is optional and specifies what FQDN your
         site should answer to.  The default virtual host has no ServerName
         directive specified, so it will respond to all requests that do not
         match a ServerName directive in another virtual host.  If you have
         just acquired the domain name ubunturocks.com and wish to host it on
         your Ubuntu server, the value of the ServerName directive in your
         virtual host configuration file should be ubunturocks.com.  Add this
         directive to the new virtual host file you created earlier
         (<filename>/etc/apache2/sites-available/mynewsite</filename>).
         </para>

                 <para>
                 You may also want your site to respond to www.ubunturocks.com, since
                 many users will assume the www prefix is appropriate.  Use the
         <emphasis>ServerAlias</emphasis> directive for this.  You may also use wildcards in the
         ServerAlias directive.
                 </para>

                 <para>
                 For example, the following configuration
         will cause your site to respond to any domain request ending in
         <emphasis>.ubunturocks.com</emphasis>.
         </para>

<programlisting>
ServerAlias *.ubunturocks.com
</programlisting>

               </listitem>
               <listitem>
                 <para>
         The <emphasis>DocumentRoot</emphasis> directive specifies where Apache should look for the
         files that make up the site.  The default value is /var/www.  No site
         is configured there, but if you uncomment the <emphasis>RedirectMatch</emphasis> directive
         in <filename>/etc/apache2/apache2.conf</filename> requests will be
         redirected to /var/www/apache2-default where the default Apache2 site
         awaits.  Change this value in your site's virtual host file, and
         remember to create that directory if necessary!
         </para>
              </listitem>
            </itemizedlist>

        <para>
            The /etc/apache2/sites-available directory is <emphasis role="bold">
            not</emphasis> parsed by Apache2.  Symbolic links in /etc/apache2/sites-enabled
            point to "available" sites.
            </para>

            <para>
            Enable the new <emphasis>VirtualHost</emphasis> using the
            <application>a2ensite</application> utility and restart Apache:
            </para>

<screen>
<command>sudo a2ensite mynewsite</command>
<command>sudo /etc/init.d/apache2 restart</command>
</screen>

            <note>
              <para>
              Be sure to replace <emphasis>mynewsite</emphasis> with a more descriptive name for the
              VirtualHost.  One method is to name the file after the <emphasis>ServerName</emphasis>
              directive of the VirtualHost.
              </para>
            </note>

            <para>
            Similarly, use the <application>a2dissite</application> utility to disable sites.  This is
            can be useful when troubleshooting configuration problems with multiple VirtualHosts:
            </para>

<screen>
<command>sudo a2dissite mynewsite</command>
<command>sudo /etc/init.d/apache2 restart</command>
</screen>

        </sect3>
        <sect3 id="default-settings" status="review">
          <title>Default Settings</title>

            <para>
            This section explains configuration of the Apache2 server
            default settings.  For example, if you add a virtual host,
            the settings you configure for the virtual host take
            precedence for that virtual host. For a directive not
            defined within the virtual host settings, the default
            value is used.
            </para>

            <itemizedlist>
            <listitem>

              <para>
              The <emphasis>DirectoryIndex</emphasis> is the default page served by the
              server when a user requests an index of a directory by
              specifying a forward slash (/) at the end of the directory
              name.
              </para>

              <para>
              For example, when a user requests the page
              http://www.example.com/this_directory/, he or she will
              get either the DirectoryIndex page if it exists, a
              server-generated directory list if it does not and the
          Indexes option is specified, or a Permission Denied page
          if neither is true.  The server will try to
              find one of the files listed in the DirectoryIndex
              directive and will return the first one it finds. If it
              does not find any of these files and if Options Indexes is
              set for that directory, the server will generate and
              return a list, in HTML format, of the subdirectories and
              files in the directory.  The default value, found in
          <filename>/etc/apache2/apache2.conf</filename> is "
          index.html index.cgi index.pl index.php index.xhtml".
          Thus, if Apache2 finds a file in a requested directory
          matching any of these names, the first will be displayed.
              </para>
            </listitem>
            <listitem>

              <para>
              The <emphasis>ErrorDocument</emphasis> directive allows you to specify a file
                 for Apache to use for specific error events.  For example,
          if a user requests a resource that does not exist, a 404
          error will occur, and per Apache2's default configuration,
          the file <filename>/usr/share/apache2/error/HTTP_NOT_FOUND.html.var
          </filename> will be displayed.  That file is not in the
          server's DocumentRoot, but there is an Alias directive in
          <filename>/etc/apache2/apache2.conf</filename> that redirects
              requests to the /error directory to <filename>/usr/share/apache2/error/</filename>.
              </para>

              <para>
          To see a list of the default ErrorDocument directives, use this
          command:
              </para>

<screen>
<command>grep ErrorDocument /etc/apache2/apache2.conf</command>
</screen>

            </listitem>
            <listitem>
              <para>
              By default, the server writes the transfer log to the file
              <filename>/var/log/apache2/access.log</filename>. You can change this on a per-site
          basis in your virtual host configuration files with the <emphasis>CustomLog</emphasis>
              directive, or omit it to accept the default, specified in <filename>
          /etc/apache2/apache2.conf</filename>.  You may also specify the file
          to which errors are logged, via the <emphasis>ErrorLog</emphasis> directive, whose default
          is <filename>/var/log/apache2/error.log</filename>.  These are kept
          separate from the transfer logs to aid in troubleshooting problems
          with your Apache2 server.  You may also specify the <emphasis>LogLevel</emphasis> (the
          default value is "warn") and the <emphasis>LogFormat</emphasis> (see <filename>
          /etc/apache2/apache2.conf</filename> for the default value).
          </para>
            </listitem>
            <listitem>
              <para>
              Some options are specified on a per-directory basis rather than per-server.
          <emphasis>Options</emphasis> is one of these directives.  A Directory stanza is enclosed in
          XML-like tags, like so:
              </para>

<programlisting>
<Directory /var/www/mynewsite>
...
</Directory>
</programlisting>

        <para>
        The <emphasis>Options</emphasis> directive within a Directory stanza accepts one or more of the
        following values (among others), separated by spaces:
            </para>

            <itemizedlist spacing="compact">
              <listitem>
                <para>
                <emphasis role="bold">ExecCGI</emphasis> - Allow
                execution of CGI scripts. CGI scripts are not
                executed if this option is not chosen.
        <tip>
                  <para>
                  Most files should not be executed as CGI scripts.  This
          would be very dangerous.  CGI scripts should kept in a directory
          separate from and outside your DocumentRoot, and only this
          directory should have the ExecCGI option set.  This is the default,
          and the default location for CGI scripts is <filename>/usr/lib/cgi-bin</filename>.
          </para>
                </tip>
        </para>
                </listitem>
                <listitem>
                  <para>
                  <emphasis role="bold">Includes</emphasis> - Allow server-side includes.
          Server-side includes allow an HTML file to <emphasis>
          include</emphasis> other files.  This is not a common option.  See
          <ulink url="http://httpd.apache.org/docs/2.2/howto/ssi.html">the Apache2
          SSI HOWTO</ulink> for more information.
                  </para>
                </listitem>
                <listitem>
                  <para>
                  <emphasis role="bold">IncludesNOEXEC</emphasis> - Allow server-side includes,
                  but disable the <emphasis>#exec</emphasis> and <emphasis>#include</emphasis>
                  commands in CGI scripts.
                  </para>
                </listitem>
                <listitem>
                  <para>
                  <emphasis role="bold">Indexes</emphasis> - Display a formatted list of the
                  directory's contents, if no <emphasis>DirectoryIndex</emphasis> (such as index.html)
                  exists in the requested directory.
                  <caution>
                    <para>
                    For security reasons, this should usually not be set, and certainly
                should not be set on your DocumentRoot directory.  Enable this option carefully on
            a per-directory basis only if you are certain you want users to see the entire
            contents of the directory.
                    </para>
                  </caution>
                  </para>
                </listitem>
                <listitem>
                  <para>
                  <emphasis role="bold">Multiview</emphasis> - Support content-negotiated multiviews;
                  this option is disabled by default for security reasons.  See the <ulink
          url="http://httpd.apache.org/docs/2.2/mod/mod_negotiation.html#multiviews">Apache2
          documentation on this option</ulink>.
                  </para>
                </listitem>
                <listitem>
                  <para>
                  <emphasis
                  role="bold">SymLinksIfOwnerMatch</emphasis> - Only follow symbolic links
                  if the target file or directory has the same owner as the link.
                  </para>
                </listitem>
              </itemizedlist>
            </listitem>
            </itemizedlist>

        </sect3>
        <sect3 id="httpd-settings" status="review">
          <title>httpd Settings</title>

          <para>
          This section explains some basic <application>httpd</application> daemon configuration settings.
          </para>

          <para>
          <emphasis role="bold">LockFile</emphasis> - The LockFile directive sets the path
          to the lockfile used when the server is compiled with either USE_FCNTL_SERIALIZED_ACCEPT
      or USE_FLOCK_SERIALIZED_ACCEPT. It must be stored on the local disk. It should be left
      to the default value unless the logs directory is located on an NFS share. If this is
      the case, the default value should be changed to a location on the local disk and to a
      directory that is readable only by root.
          </para>

      <para>
          <emphasis role="bold">PidFile</emphasis> - The PidFile directive sets the file in which the server
      records its process ID (pid). This file should only be readable by root. In most cases, it should be left
      to the default value.
          </para>

          <para>
          <emphasis role="bold">User</emphasis> - The User directive sets the userid used by the server to answer requests. This
          setting determines the server's access. Any files inaccessible to this user will also be inaccessible to your website's visitors.
          The default value for User is www-data.
          </para>

          <warning>
            <para>
            Unless you know exactly what you are doing, do not set the User directive to root. Using root as the User will
            create large security holes for your Web server.
            </para>
          </warning>

          <para>The Group directive is similar to the User directive. Group sets the group under which the server will answer requests.
          The default group is also www-data.
          </para>

        </sect3>
        <sect3 id="apache-modules" status="review">
          <title>Apache Modules</title>

          <para>
          Apache is a modular server. This implies that only the most
          basic functionality is included in the core server. Extended
          features are available through modules which can be loaded
          into Apache. By default, a base set of modules is included in
          the server at compile-time. If the server is compiled to use
          dynamically loaded  modules, then modules can be compiled
          separately, and added at any time using the LoadModule
          directive. Otherwise, Apache must be recompiled to add or
          remove modules.
          </para>

          <para>
          Ubuntu compiles Apache2 to allow the dynamic
          loading of modules.  Configuration directives may be conditionally
      included on the presence of a particular module by enclosing
          them in an <emphasis><IfModule></emphasis> block.
          </para>

          <para>
          You can install additional Apache2 modules and use them
          with your Web server.  For example, run the following command from a
          terminal prompt to install the <emphasis>MySQL Authentication</emphasis> module:
          </para>

<screen>
<command>sudo apt-get install libapache2-mod-auth-mysql</command>
</screen>

          <para>
          See the <filename>/etc/apache2/mods-available</filename> directory, for additional modules.
          </para>

          <para>
          Use the <application>a2enmod</application> utility to
          enable a module:
          </para>

<screen>
<command>sudo a2enmod auth_mysql</command>
<command>sudo /etc/init.d/apache2 restart</command>
</screen>

          <para>
          Similarly, <application>a2dismod</application> will disable a module:
          </para>

<screen>
<command>sudo a2dismod auth_mysql</command>
<command>sudo /etc/init.d/apache2 restart</command>
</screen>

        </sect3>
      </sect2>
      <sect2 id="https-configuration" status="review">
        <title>HTTPS Configuration</title>

          <para>
          The <application>mod_ssl</application> module adds
          an important feature to the Apache2 server - the ability to
          encrypt communications.  Thus, when your browser is
          communicating using SSL, the
          https:// prefix is used at the beginning of the Uniform
          Resource Locator (URL) in the browser navigation bar.
          </para>

          <para>
          The <application>mod_ssl</application> module is available in
          <application>apache2-common</application> package. Execute the following command from a terminal prompt to
          enable the <application>mod_ssl</application> module:
          </para>

<screen>
<command>sudo a2enmod ssl</command>
</screen>

          <para>
          There is a default HTTPS configuration file in <filename>/etc/apache2/sites-available/default-ssl</filename>.
          In order for <application>Apache</application> to provide HTTPS,
          a <emphasis>certificate</emphasis> and <emphasis>key</emphasis> file are also needed.  The default HTTPS
          configuration will use a certificate and key generated by the <application>ssl-cert</application> package.  They
          are good for testing, but the auto-generated certificate and key should be replaced by a certificate specific
          to the site or server. For information on generating a key and obtaining a certificate see
          <xref linkend="certificates-and-security"/>
          </para>

      <para>
          To configure <application>Apache</application> for HTTPS, enter the following:
          </para>

<screen>
<command>sudo a2ensite default-ssl</command>
</screen>

            <note>
              <para>
              The directories <filename>/etc/ssl/certs</filename> and <filename>/etc/ssl/private</filename> are the
              default locations.  If you install the certificate and key in another directory make sure to change
              <emphasis>SSLCertificateFile</emphasis> and <emphasis>SSLCertificateKeyFile</emphasis> appropriately.
              </para>
            </note>

            <para>
            With Apache now configured for HTTPS, restart the service to enable the new settings:
            </para>


<screen>
<command>sudo /etc/init.d/apache2 restart</command>
</screen>


            <note>
              <para>
              Depending on how you obtained your certificate you may need to
              enter a passphrase when <application>Apache</application> starts.
              </para>
            </note>

            <para>
         You can access the secure server pages by typing
            https://your_hostname/url/ in your browser address bar.
            </para>

      </sect2>
      <sect2 id="http-references" status="review">
        <title>References</title>

          <itemizedlist>
            <listitem>
            <para>
            <ulink url="http://httpd.apache.org/docs/2.2/">Apache2 Documentation</ulink> contains in depth
            information on Apache2 configuration directives. Also, see the <application>apache2-doc</application>
            package for the official Apache2 docs.
            </para>
          </listitem>
          <listitem>
            <para>
            See the <ulink url="http://www.modssl.org/docs/">Mod SSL Documentation</ulink> site for more
            SSL related information.
            </para>
          </listitem>
          <listitem>
            <para>
            O'Reilly's <ulink url="http://oreilly.com/catalog/9780596001919/">Apache Cookbook</ulink> is
            a good resource for accomplishing specific Apache2 configurations.
            </para>
          </listitem>
          <listitem>
            <para>
            For Ubuntu specific Apache2 questions, ask in the <emphasis>#ubuntu-server</emphasis> IRC channel on
            <ulink url="http://freenode.net/">freenode.net</ulink>.
            </para>
          </listitem>
        </itemizedlist>

      </sect2>
    </sect1>

    <sect1 id="php5" status="review">
        <title>PHP5 - Scripting Language</title>
      <para>PHP is a general-purpose scripting language suited for Web
      development. The PHP script can be embedded into HTML. This
      section explains how to install and configure PHP5 in Ubuntu
      System with Apache2 and MySQL.</para>
      <para> This section assumes you have installed and configured
      Apache 2 Web Server and MySQL Database Server. You can refer to
      Apache 2 section and MySQL sections in this document to install and
      configure Apache 2 and MySQL respectively.</para>

<sect2 id="php5-installation" status="review">
  <title>Installation</title>
      <para>The PHP5 is available in Ubuntu Linux. </para>

      <procedure><step><para>
      To install PHP5 you
      can enter the following command in the terminal prompt:

<screen>
<command>sudo apt-get install php5 libapache2-mod-php5</command>
</screen>
</para>

      <para>You can run PHP5 scripts from command line. To run PHP5 scripts
      from command line you should install
      <application>php5-cli</application> package. To install
      <application>php5-cli</application> you can enter the following
      command in the terminal prompt:
<screen>
<command>sudo apt-get install php5-cli</command>
</screen>
</para>
      <para>
      You can also execute PHP5 scripts without installing PHP5 Apache
      module. To accomplish this, you should install
      <application>php5-cgi</application> package. You can run the
      following command in a terminal prompt to install
      <application>php5-cgi</application> package:
<screen>
<command>sudo apt-get install php5-cgi</command>
</screen>
      </para>
      <para>To use <application>MySQL</application> with PHP5 you should install
      <application>php5-mysql</application> package. To install
      <application>php5-mysql</application> you can enter the following
      command in the terminal prompt:
<screen>
<command>sudo apt-get install php5-mysql</command>
</screen>
</para>
      <para>Similarly, to use <application>PostgreSQL</application> with PHP5 you should install
      <application>php5-pgsql</application> package. To install
      <application>php5-pgsql</application> you can enter the following
      command in the terminal prompt:
<screen>
<command>sudo apt-get install php5-pgsql</command>
</screen>
      </para>
            </step>
        </procedure>
      </sect2>
      <sect2 id="php5-configuration" status="review">
        <title>Configuration</title>
          <para>
          Once you install PHP5, you can run PHP5 scripts from your web
          browser. If you have installed
          <application>php5-cli</application> package, you can run PHP5
          scripts from your command prompt.
          </para>

          <para>
          By default, the Apache 2 Web server is configured to run PHP5
          scripts. In other words, the PHP5 module is enabled in Apache2
          Web server automatically when you install the module. Please
          verify if the files
          <filename>/etc/apache2/mods-enabled/php5.conf</filename> and
          <filename>/etc/apache2/mods-enabled/php5.load</filename>
          exist. If they do not exists, you can enable the module using
          <command>a2enmod</command> command.
          </para>

          <para>Once you install PHP5 related packages and enabled PHP5
          Apache 2 module, you should restart Apache2 Web server to run
          PHP5 scripts. You can run the following command at a terminal
          prompt to restart your web server:
<screen><command>sudo /etc/init.d/apache2 restart</command> </screen>
          </para>
      </sect2>
      <sect2 id="php5-testing" status="review">
        <title>Testing</title>
          <para>To verify your installation, you can run following PHP5
          phpinfo script:
          </para>
<programlisting>
<?php
print_r (phpinfo());
?>
</programlisting>
          <para>
          You can save the content in a file
          <filename>phpinfo.php</filename> and place it
          under <command>DocumentRoot</command> directory of Apache2 Web
          server. When point your browser to
          <filename>http://hostname/phpinfo.php</filename>, it would
          display values of various PHP5 configuration parameters.
      </para>
      </sect2>
      <sect2 id="php5-references">
        <title>References</title>

        <itemizedlist>
          <listitem>
            <para>
            For more in depth information see <ulink url="http://www.php.net/docs.php">php.net</ulink> documentation.
            </para>
          </listitem>
          <listitem>
            <para>
            There are a plethora of books on PHP.  Two good books from O'Reilly are
            <ulink url="http://oreilly.com/catalog/9780596005603/">Learning PHP 5</ulink> and the
            <ulink url="http://oreilly.com/catalog/9781565926813/">PHP Cook Book</ulink>.
            </para>
          </listitem>
        </itemizedlist>

      </sect2>
    </sect1>

    <sect1 id="squid" status="review">
        <title>Squid - Proxy Server</title>
          <para>
          Squid is a full-featured web proxy cache server application which provides proxy and cache services for Hyper Text
          Transport Protocol (HTTP), File Transfer Protocol (FTP), and other popular network protocols.  Squid can implement
          caching and proxying of Secure Sockets Layer (SSL) requests and caching of Domain Name Server (DNS) lookups, and perform
          transparent caching. Squid also supports a wide variety of caching protocols, such as Internet Cache Protocol, (ICP)
          the Hyper Text Caching Protocol, (HTCP) the Cache Array Routing Protocol (CARP), and the Web Cache Coordination
          Protocol. (WCCP)
          </para>
          <para>
          The Squid proxy cache server is an excellent solution to a variety of proxy and caching server needs, and scales from
          the branch office to enterprise level networks while providing extensive, granular access control mechanisms and
          monitoring of critical parameters via the Simple Network Management Protocol (SNMP).  When selecting a computer system
          for use as a dedicated Squid proxy, or caching servers, ensure your system is configured with a large amount of physical
          memory, as Squid maintains an in-memory cache for increased performance.
          </para>
      <sect2 id="squid-installation" status="review">
        <title>Installation</title>
          <para>
            At a terminal prompt, enter the following command to install the Squid server:
          </para>
          <para>
<screen>
<command>sudo apt-get install squid</command>
</screen>
          </para>
      </sect2>
      <sect2 id="squid-configuration" status="review">
        <title>Configuration</title>
          <para>
            Squid is configured by editing the directives contained within the <filename>/etc/squid/squid.conf</filename> configuration file.
            The following examples illustrate some of the directives which may be modified to affect the behavior of the Squid server.
            For more in-depth configuration of Squid, see the References section.
          </para>
             <tip>
               <para>Prior to editing the configuration file, you should make a copy of the original file and protect it
               from writing so you will have the original settings as a reference, and to re-use as necessary.
               </para>
               <para>Copy the <filename>/etc/squid/squid.conf</filename> file and protect it from writing with the following commands entered at a terminal prompt:
               </para>
         </tip>
               <para>
<screen>
<command>sudo cp /etc/squid/squid.conf /etc/squid/squid.conf.original</command>
<command>sudo chmod a-w /etc/squid/squid.conf.original</command>
</screen>
               </para>
            <para>
           <itemizedlist>
               <listitem>
                  <para>
                  To set your Squid server to listen on TCP port 8888 instead of the default TCP port 3128, change
                  the http_port directive as such:
                  </para>
<programlisting>
http_port 8888
</programlisting>
               </listitem>
                <listitem>
                  <para>
                  Change the visible_hostname directive in order to give the Squid server a specific hostname.  This hostname
                  does not necessarily need to be the computer's hostname. In this example it is set to <emphasis>weezie</emphasis>
                  </para>
<programlisting>
visible_hostname weezie
</programlisting>
               </listitem>
               <listitem>
                  <para>
                     Again, Using Squid's access control, you may configure use of Internet services proxied by Squid
                     to be available only users with certain Internet Protocol (IP) addresses.  For example, we will illustrate access
                     by users of the 192.168.42.0/24 subnetwork only:
                  </para>
                  <para>
                     Add the following to the <emphasis role="bold">bottom</emphasis> of the ACL section of your <filename>/etc/squid/squid.conf</filename> file:
                  </para>
<programlisting>
acl fortytwo_network src 192.168.42.0/24
</programlisting>
                  <para>
                     Then, add the following to the <emphasis role="bold">top</emphasis> of the http_access section of your
                     <filename>/etc/squid/squid.conf</filename> file:
                  </para>
<programlisting>
http_access allow fortytwo_network
</programlisting>
               </listitem>
               <listitem>
                  <para>
                     Using the excellent access control features of Squid, you may configure use of Internet services proxied by Squid
                     to be available only during normal business hours.  For example, we'll illustrate access by employees of a business
                     which is operating between 9:00AM and 5:00PM, Monday through Friday, and which uses the 10.1.42.0/42 subnetwork:
                  </para>
                  <para>
                     Add the following to the <emphasis role="bold">bottom</emphasis> of the ACL section of your <filename>/etc/squid/squid.conf</filename> file:
                  </para>
<programlisting>
acl biz_network src 10.1.42.0/24
acl biz_hours time M T W T F 9:00-17:00
</programlisting>
                  <para>
                     Then, add the following to the <emphasis role="bold">top</emphasis> of the http_access section of your
                     <filename>/etc/squid/squid.conf</filename> file:
                  </para>
<programlisting>
http_access allow biz_network biz_hours
</programlisting>
               </listitem>
          </itemizedlist>
          </para>
          <note>
      <para>
          After making changes to the <filename>/etc/squid/squid.conf</filename> file, save the file and restart the <application>squid</application>
          server application to effect the changes using the following command entered at a terminal prompt:
          </para>
          </note>
          <para>
<screen>
<command>sudo /etc/init.d/squid restart</command>
</screen>
          </para>
      </sect2>
      <sect2 id="squid-references" status="review">
      <title>References</title>
      <para>
      <ulink url="http://www.squid-cache.org/">Squid Website</ulink>
      </para>
      </sect2>
    </sect1>

    <sect1 id="ruby-on-rails" status="review">
        <title>Ruby on Rails</title>
    <para>Ruby on Rails is an open source web framework for developing
    database backed web applications. It is optimized for sustainable
    productivity of the programmer since it lets the programmer to write
    code by favouring convention over configuration.</para>

    <sect2 id="ruby-on-rails-installation" status="review">
      <title>Installation</title>
        <para>
        Before installing <application>Rails</application> you should install <application>Apache</application>
        and <application>MySQL</application>.
        To install the <application>Apache</application> package, please refer to
        <xref linkend="httpd"/>.  For instructions on installing
        <application>MySQL</application> refer to
        <xref linkend="mysql"/>.
    </para>
      <para>
          Once you have <application>Apache</application> and
        <application>MySQL</application> packages installed,
          you are ready to install <application>Ruby on
        Rails</application> package.
      </para>

      <para>
      To install the <application>Ruby</application> base packages and
      <application>Ruby on Rails</application>,
      you can enter the following command in the terminal prompt:
      </para>
<screen>
<command>sudo apt-get install rails</command>
</screen>

    </sect2>
    <sect2 id="ruby-on-rails-configuration" status="review">
    <title>Configuration</title>
    <para>
        Modify the <filename>/etc/apache2/sites-available/default</filename>
    configuration file to setup your domains.
    </para>
    <para>
        The first thing to change is the <emphasis>DocumentRoot</emphasis>
      directive:
    </para>
<programlisting>
DocumentRoot /path/to/rails/application/public
</programlisting>
    <para>
        Next, change the <Directory
      "/path/to/rails/application/public"> directive:
    </para>
<programlisting>
<Directory "/path/to/rails/application/public">
        Options Indexes FollowSymLinks MultiViews ExecCGI
        AllowOverride All
        Order allow,deny
        allow from all
        AddHandler cgi-script .cgi
</Directory>
</programlisting>

    <para>
    You should also enable the <application>mod_rewrite</application>
    module for Apache.  To enable <application>mod_rewrite</application>
    module, please enter the following command in a terminal prompt:
    </para>
<screen>
<command>sudo a2enmod rewrite</command>
</screen>

    <para>
    Finally you will need to change the ownership of the <filename>/path/to/rails/application/public</filename>
    and <filename>/path/to/rails/application/tmp</filename> directories to the user used to run the
    <application>Apache</application> process:
    </para>
<screen>
<command>sudo chown -R www-data:www-data /path/to/rails/application/public</command>
<command>sudo chown -R www-data:www-data /path/to/rails/application/tmp</command>
</screen>

    <para>That's it! Now you have your Server ready for your
    <application>Ruby on Rails</application> applications.
    </para>
    </sect2>
    <sect2 id="ruby-on-rails-references" status="review">
      <title>References</title>

        <itemizedlist>
          <listitem>
            <para>
            See the <ulink url="http://rubyonrails.org/">Ruby on Rails</ulink> website for more information.
            </para>
          </listitem>
          <listitem>
            <para>
            Also <ulink url="http://pragprog.com/titles/rails3/agile-web-development-with-rails-third-edition">Agile Development with Rails</ulink>
            is a great resource.
            </para>
          </listitem>
        </itemizedlist>

    </sect2>
  </sect1>

    <sect1 id="tomcat" status="review">
        <title>Apache Tomcat</title>
        <para>Apache Tomcat is a web container that allows you to serve Java Servlets
        and JSP (Java Server Pages) web applications.</para>
        <para>The <application>Tomcat 6.0</application> packages in Ubuntu support
        two different ways of running Tomcat. You can install them as a classic
        unique system-wide instance, that will be started at boot time and will run
        as the tomcat6 unpriviledged user. But you can also deploy private
        instances that will run with your own user rights, and that you should
        start and stop by yourself. This second way is particularly useful in a
        development server context where multiple users need to test on their own
        private Tomcat instances.</para>

        <sect2 id="tomcat-installation" status="review">
            <title>System-wide installation</title>
            <para>To install the <application>Tomcat</application> server,
            you can enter the following command in the terminal prompt:</para>
<screen>
<command>sudo apt-get install tomcat6</command>
</screen>
            <para>This will install a Tomcat server with just a default ROOT webapp
            that displays a minimal "It works" page by default.</para>
        </sect2>

    <sect2 id="tomcat-configuration" status="review">
        <title>Configuration</title>
        <para>Tomcat configuration files can be found in
            <filename>/etc/tomcat6</filename>. Only a few common configuration tweaks
            will be described here, please see
            <ulink url="http://tomcat.apache.org/tomcat-6.0-doc/index.html">Tomcat
            6.0 documentation</ulink> for more.</para>
            <sect3 id="tomcat-configuration-ports" status="review">
                <title>Changing default ports</title>
                <para>By default Tomcat 6.0 runs a HTTP connector on port 8080 and an
                AJP connector on port 8009. You might want to change those default
                ports to avoid conflict with another server on the system. This is
                done by changing the following lines in
                <filename>/etc/tomcat6/server.xml</filename>:</para>
<programlisting>
<Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />
...
<Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />
</programlisting>
            </sect3>
            <sect3 id="tomcat-configuration-jvm" status="review">
                <title>Changing JVM used</title>
                <para>By default Tomcat will run preferably with OpenJDK-6, then try
                Sun's JVM, then try some other JVMs. If you have various JVMs
                installed, you can set which should be used by setting JAVA_HOME in
                <filename>/etc/default/tomcat6</filename>:</para>
<programlisting>
JAVA_HOME=/usr/lib/jvm/java-6-sun
</programlisting>
            </sect3>
            <sect3 id="tomcat-configuration-users" status="review">
                <title>Declaring users and roles</title>
                <para>Usernames, passwords and roles (groups) can be defined centrally
                in a Servlet container. In Tomcat 6.0 this is done in the
                <filename>/etc/tomcat6/tomcat-users.xml</filename> file:</para>
<programlisting>
<role rolename="admin"/>
<user username="tomcat" password="s3cret" roles="admin"/>
</programlisting>
            </sect3>
    </sect2>

        <sect2 id="tomcat-webapps" status="review">
            <title>Using Tomcat standard webapps</title>
            <para>Tomcat is shipped with webapps that you can install
            for documentation, administration or demo purposes.</para>
            <sect3 id="tomcat-installation-docs" status="review">
                <title>Tomcat documentation</title>
                <para>The <application>tomcat6-docs</application> package contains
                Tomcat 6.0 documentation, packaged as a webapp that you can access by
                default at http://yourserver:8080/docs. You can install it by entering
                the following command in the terminal prompt:</para>
<screen>
<command>sudo apt-get install tomcat6-docs</command>
</screen>
            </sect3>
            <sect3 id="tomcat-installation-admin" status="review">
                <title>Tomcat administration webapps</title>
                <para>The <application>tomcat6-admin</application> package contains
                two webapps that can be used to administer the Tomcat server using a
                web interface. You can install them by entering the
                following command in the terminal prompt:</para>
<screen>
<command>sudo apt-get install tomcat6-admin</command>
</screen>
                <para>The first one is the <emphasis>manager</emphasis> webapp, which
                you can access by default at http://yourserver:8080/manager/html. It is
                primarily used to get server status and restart webapps.</para>
                <note><para>Access to the <emphasis>manager</emphasis> application is
                protected by default: you need to define a user with the role "manager"
                in <filename>/etc/tomcat6/tomcat-users.xml</filename>
                before you can access it.</para></note>
                <para>The second one is the <emphasis>host-manager</emphasis> webapp,
                which you can access by default at
                http://yourserver:8080/host-manager/html.
                It can be used to create virtual hosts dynamically.</para>
                <note><para>Access to the <emphasis>host-manager</emphasis> application is
                also protected by default: you
                need to define a user with the role "admin" in
                <filename>/etc/tomcat6/tomcat-users.xml</filename>
                before you can access it.</para></note>
                <para>For security reasons, the tomcat6 user cannot write to the
                <filename>/etc/tomcat6</filename> directory by default. Some features
                in these admin webapps (application deployment, virtual host creation)
                need write access to that directory. If you want to use these
                features execute the following, to give users in the tomcat6 group the necessary
                rights:</para>
<screen>
<command>sudo chgrp -R tomcat6 /etc/tomcat6</command>
<command>sudo chmod -R g+w /etc/tomcat6</command>
</screen>

            </sect3>
            <sect3 id="tomcat-installation-examples" status="review">
                <title>Tomcat examples webapps</title>
                <para>The <application>tomcat6-examples</application> package contains
                two webapps that can be used to test or demonstrate Servlets and JSP
                features, which you can access them by default at
                http://yourserver:8080/examples. You can install them by entering the
                following command in the terminal prompt:</para>
<screen>
<command>sudo apt-get install tomcat6-examples</command>
</screen>
            </sect3>
    </sect2>

        <sect2 id="tomcat-user" status="review">
            <title>Using private instances</title>
            <para>Tomcat is heavily used in development and testing scenarios
            where using a single system-wide instance doesn't meet the requirements
            of multiple users on a single system. The Tomcat 6.0 packages in
            Ubuntu come with tools to help deploy your own user-oriented instances,
            allowing every user on a system to run (without root rights) separate
            private instances while still using the system-installed
            libraries.</para>
            <note><para>It is possible to run the system-wide instance and the private
            instances in parallel, as long as they do not use the same TCP
            ports.</para></note>
            <sect3 id="tomcat-user-install" status="review">
                <title>Installing private instance support</title>
                <para>You can install everything necessary to run private instances
                by entering the following command in the terminal prompt:</para>
<screen>
<command>sudo apt-get install tomcat6-user</command>
</screen>
            </sect3>
            <sect3 id="tomcat-user-create" status="review">
                <title>Creating a private instance</title>
                <para>You can create a private instance directory by entering the
                following command in the terminal prompt:</para>
<screen>
<command>tomcat6-instance-create my-instance</command>
</screen>
                <para>This will create a new <filename>my-instance</filename> directory
                with all the necessary subdirectories and scripts.
                You can for example install your common libraries in the
                <filename>lib/</filename> subdirectory and deploy your webapps in the
                <filename>webapps/</filename> subdirectory. No webapps are deployed
                by default.</para>
            </sect3>
            <sect3 id="tomcat-user-config" status="review">
                <title>Configuring your private instance</title>
                <para>You will find the classic Tomcat configuration files for your
                private instance in the <filename>conf/</filename>
                subdirectory. You should for
                example certainly edit the <filename>conf/server.xml</filename> file
                to change the default ports used by your private Tomcat instance to
                avoid conflict with other instances that might be running.</para>
            </sect3>
            <sect3 id="tomcat-user-start" status="review">
                <title>Starting/stopping your private instance</title>
                <para>You can start your private instance by entering the following
                command in the terminal prompt (supposing  your instance is located
                in the <filename>my-instance</filename> directory):</para>
<screen>
<command>my-instance/bin/startup.sh</command>
</screen>
                <note><para>You should check the <filename>logs/</filename> subdirectory for
                any error. If you have a <emphasis>java.net.BindException: Address
                already in use<null>:8080</emphasis> error, it means that the
                port you're using is already taken and that you should change it.
                </para></note>
                <para>You can stop your instance by entering the following
        command in the terminal prompt (supposing  your instance is located
        in the <filename>my-instance</filename> directory):</para>
<screen>
<command>my-instance/bin/shutdown.sh</command>
</screen>
            </sect3>
        </sect2>
                <sect2 id="tomcat-references" status="review">
                  <title>References</title>

                  <itemizedlist>
                    <listitem>
                      <para>
                      See the <ulink url="http://tomcat.apache.org/">Apache Tomcat</ulink> website for more information.
                      </para>
                    </listitem>
                    <listitem>
                      <para>
                      <ulink url="http://oreilly.com/catalog/9780596003180/">Tomcat: The Definitive Guide</ulink> is a good
                      resource for building web applications with Tomcat.
                      </para>
                    </listitem>
                    <listitem>
                      <para>
                      For additional books see the <ulink url="http://wiki.apache.org/tomcat/Tomcat/Books">Tomcat Books</ulink> list page.
                      </para>
                    </listitem>
                  </itemizedlist>
                </sect2>

    </sect1>
</chapter>