Meeting 3: Advanced Apache Topics

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Meeting 3 Advanced Apache Topics

• Rutgers University Internet Institute
• Instructor Chris Uriarte
• (non IPVH exc)

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Virtual Hosting

• General term used when you run more than one
  website on a single system.
• Allows ISPs and hosting providers to make money
  by sharing resources among clients. Allows
  companies and individuals to save time and money
  - a single machine can host many websites.

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Options for Hosting More than One Website on a
Single System

• Run separate instances of httpd servers httpd f
  /usr/local/apache/conf/httpd-virtual.conf
• Run a server that will listen on multiple ports
  and serve different content depending on the
  port.
• True Virtual Hosting - Allows multiple IP address
  and/or host names to be served through a single
  Apache server.
• IP-Based
• Name-Based (not supported by very early Web
  browsersNetscape 2.0/IE 3.0)

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Virtual Hosting IP Based

• You must configure your machine to listen for
  multiple IP addresses. One NIC binds to multiple
  IP addresses
• One hostname is associated with each IP address

SERVER
www.yahoo.com
216.32.74.52
NIC
216.115.105.243
sports.yahoo.com
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Virtual Hosting Name Based

• A machine can host multiple websites using only 1
  IP address
• All hostnames have the same IP address
• Becoming more and more popular.

SERVER
some.mydomain.com
165.145.26.110
NIC
www.hisdomain.com
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Setting-Up IP-Based Virtual Hosting An Overview

• Once you have secured the domain names/hostnames
  you want to use for your website, you need to
  assign each of them a unique IP address.
• Some ISPs can assign you additional IP addresses.
  
• Blocks of IP addresses are usually assigned with
  business T1s or DSL lines.

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Setting-Up IP-Based Virtual Hosting, Cont.

• You need to have DNS properly configured for your
  domains, e.g. The world needs to know that
  www.yourdomain.com is at the IP address
  123.23.34.56.
• Remember, your ISP can usually provide DNS
  service for your domains.

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IP-Based Virtual Hosting Setting Up Your Machine

• Your web server needs to be configured to listen
  for the IP addresses related to your websites
• UNIX-based OSs allow you to configure multiple IP
  addresses using the ifconfig command (must be run
  as root)
• Usage ifconfig interfaceltsub-numbergt IP
• e.g ifconfig eth00 165.230.30.71
• ifconfig eth01 165.230.30.72
• WinNT IP setup through Network control panel.

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Configuring Apache for IP-Based Virtual Hosting

• Configuring Apache for Virtual Hosting is quite
  simple Simply add a ltVirtualHostgt block within
  the httpd.conf file.
• Format
• ltVirtualHost IP-or-HOSTNAMEPortgt
• Any Valid httpd.conf directives
• lt/VirtualHostgt
• Required for each Virtual Host website your are
  usingtherefore your httpd.conf can have multiple
  ltVirtualHostgt blocks.

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IP-Based VH Configuration cont.

• Typical ltVirtualHostgt block in httpd.conf
• ltVirtualHost www.bearsnest.orggt
• DocumentRoot /home/www/bearsnest/htdocs
• ServerAdmin chrisjur_at_cju.com
• ServerName www.bearsnest.org
• ErrorLog logs/bears-error_log
• TransferLog logs/bears-access_log
• Redirect /adprotech http//www.adprotech.com
• Alias /staff /home/chrisjur/htdocs/bn/staff
• lt/VirtualHostgt
• The key Vitual hosts will have their own unique
  DocumentRoot different content for different
  sties.

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Steps for Setting-Up Name-Based Virtual Hosting

• When setting up Name-based virtual hosts, you
  need to add the special NameVirtialHost Directive
  to your httpd.conf
• NameVirtualHost ltYour IP Addressgt
• Which tells Apache the single IP address you will
  use for all your websites.
• Now simply add ltVirtualHostgt blocks for each of
  your website domains.

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Name-Based VH Examples

• NameVirtualHost 165.230.30.68
• ltVirtualHost www.yoursite.orggt
• DocumentRoot /home/www/yoursite/htdocs
• ServerAdmin you_at_yoursite.com
• ServerName www.yoursite.com
• ErrorLog logs/yoursite-error_log
• lt/VirtualHostgt
• ltVirtualHost www.mysite.comgt
• DocumentRoot /home/www/mysite/htdocs
• ServerAdmin me_at_mysite.com
• ServerName www.mysite.org
• ErrorLog logs/mysite-error_log
• lt/VirtualHostgt

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Virtual Hosting Recap

• Get your DNS configured for each domain
• IP-based Virtual Hosting vs. Name-based Virtual
  Hosting
• Configure your server for multiple IP addresses
  if using IP-based Virtual Hosting
• Create new directories for new Document Roots
• Add ltVirtualHostgt blocks to your httpd.conf

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Delivering Dynamic Content

• Two ways of delivering dynamic content for the
  Web client-side or server-side technologies
• Client-Side
• Elements are downloaded to the browser and
  execute on the clients system.
• Examples JavaScript, Java Applets, client-side
  image maps.
• Web server administrator needs to see that MIME
  types are set correctly.

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Dynamic Content, cont.

• Server-Side
• Server processes on-the-fly content that is
  passed to client browser.
• Examples server-side includes, CGI (Common
  Gateway Interface), server-side image maps, ASP
  (Active Server Pages), Java Servlets. PHP
• Server-side technologies generally require
  additional configuration of the Web server in
  order to function properly. Usually require
  specific Apache modules.
• Enabling server-side technologies generally has
  security implications.

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Server-Side Includes

• Server-side includes are directives that can be
  placed in HTML documents to execute other
  programs or to output data.
• Requires mod_include.
• To enable SSI, make the following modifications
  to httpd.conf
• Options Includes (or IncludesNOEXEC)
• The options directive only works within a
  specific Directory or VirtualHost container.

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Enabling Server Side Includes, cont

• To tell Apache how to interpret SSI documents,
  add the following to httpd.conf
• AddType text/html .shtml
• AddHandler server-parsed .shtml
• These lines are usually commented out by default,
  so you just need to uncomment them.
• All files with indicated extension(s) will be
  parsed by Apache server prior to being
  transmitted to the client, e.g. web page files
  that end with .shtml can contain SSIs.

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Server-Side Includes Examples

• The general form of the SSI directive is
  lt!--command parametervalue--gt For example
• lt!include fileinclude.html--gt
• Will insert the contents of the file file
  include.html when displayed in the clients
  browser.
• lt!echo varLAST_MODIFIED--gt
• Prints the last time your HTML file was modified.
  

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Server Side Includes, cont.

• The Server Side Include in the .html file is
  evaluated by Apache and the output is displayed
  to the client.
• See Appendix E in Professional Apache for a guide
  to includes that Apache understands.
• Check out http//iti.rutgers.edu/chrisjur/ssi.sht
  ml for an example ( source file is
  /home/chrisjur/public_hthml/ssi.html on
  iti.rutgers.edu server)

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CGI

• CGI (Common Gateway Interface) is a protocol for
  getting, processing, and returning information
  through Web pages.
• CGI programs or scripts can be written in a
  variety of languages including Perl, Python, VB
  Script, JavaScript, and C.
• CGI scripts are generally triggered by data
  supplied by the client.

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Enabling CGI

• There are two ways to enable Apache to recognize
  CGI scripts
• To allow CGI scripts in one system-wide directory
  outside of the document root (All CGI programs
  must be placed in one directory)
• ScriptAlias /cgi-bin /home/itiXXXX/apache/cgi-bin
  /
• Within a container
• Options ExecCGI ltother optionsgt
• SetHandler cgi-script
• To enable files with only specific extensions as
  CGI scripts use AddHandler instead of
• SetHandler AddHandler cgi-script .cgi

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Enabling CGI Example 1

• Sometimes its convenient to have one
  centrialized cgi-bin directory where all CGI
  programs are kept.
• You can access all the scripts through
  http//www.domain.com/cgi-bin/scriptname
• To do this at the following line to httpd.conf
• ScriptAlias /cgi-bin /home/itiXXXX/apache/cgi-bin
  /

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Enabling CGI Example 2

• You can enable CGI scripts to be placed in any
  directory by specifying some CGI directives in a
  directory container within the httpd.conf or an
  .htaccess file. This allows CGI execution in the
  directory specified
• ltDirectory /home/user/htdocsgt
• Options ExecCGI (other options)
• SetHandler cgi-script
• lt/Directorygt

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Limiting CGI Access

• If you do not have Options ExecCGI or a
  ScriptAlias directive, the execution of CGI
  programs will be denied.
• You can limit CGI access to only programs that
  end with a specific extension
• SetHandler AddHandler cgi-script .cgi
• (limits CGI execution to programs that only end
  in .cgi)

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CGI Examples

• http//iti.rutgers.edu/chrisjur/cgi-bin/test.cgi
  - CGI script written in Perl, simply outputs
  current time and the end-users browser type
  (source at /home/chrisjur/public_html/cgi-bin/test
  .cgi)
• http//iti.rutgers.edu/chrisjur/cgi-bin/shell.cgi
  - Written as a shell script in, prints current
  date/time and lists files in its directories
  (source at /home/chrisjur/public_html/cgi-bin/shel
  l.cgi)

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More CGI Examples

• http//iti.rutgers.edu/chrisjur/feedback.html -
  More traditional example of what CGI is used for.
  An HTML form posts to a CGI script written in
  Perl (/home/chrisjur/public_html/cgi-bin/feedback.
  cgi) which emails form contents to a recipient
  and performs some validation logic.

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Exercise Enabling CGI

• Enable CGI via the ScriptAlias directive in your
  httpd.conf. Specify a cgi-bin directory to place
  all your CGI scripts.
• Copy /home/chrisjur/test.cgi script to your
  cgi-bin directory. Make the test.cgi script
  executeable (chmod ax test.cgi)
• Access the script via http//iti.rutgers.eduYourP
  ort/cgi-bin/test.cgi