Apache 2 Web Server on Ubuntu 9.10 (Karmic)

This tutorial explains how to install and configure the Apache web server on Ubuntu 9.10 (Karmic). All configuration will be done through the terminal; make sure you are logged in as root via SSH. If you have not followed the Setting Up and Securing a Compute Instance guide, it is recommended that you do so prior to beginning this guide. Also note that if you’re looking to install a full LAMP stack, you may want to consider using our LAMP guide for Ubuntu 9.10.

Basic System Configuration

Make sure your /etc/hosts file contains sensible values. In the example file below, you would replace “12.34.56.78” with your Linode’s IP address, and “servername.example.com” with your Linode’s fully qualified domain name (FQDN). It is advisable to use something unique and memorable for “servername” in this file.

File: /etc/hosts

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## main & restricted repositories deb http://us.archive.ubuntu.com/ubuntu/ karmic main restricted deb-src http://us.archive.ubuntu.com/ubuntu/ karmic main restricted deb http://security.ubuntu.com/ubuntu karmic-security main restricted deb-src http://security.ubuntu.com/ubuntu karmic-security main restricted ## universe repositories deb http://us.archive.ubuntu.com/ubuntu/ karmic universe deb-src http://us.archive.ubuntu.com/ubuntu/ karmic universe deb http://us.archive.ubuntu.com/ubuntu/ karmic-updates universe deb-src http://us.archive.ubuntu.com/ubuntu/ karmic-updates universe deb http://security.ubuntu.com/ubuntu karmic-security universe deb-src http://security.ubuntu.com/ubuntu karmic-security universe

Install Apache 2

Make sure your package repositories and installed programs are up to date by issuing the following commands:

apt-get update
apt-get upgrade --show-upgraded

Enter the following command to install the Apache 2 web server, its documentation and a collection of utilities.

apt-get install apache2 apache2-doc apache2-utils

Install Support for Scripting

The following commands are optional, and should be run if you want to have support within Apache for server-side scripting in PHP, Ruby, Python, or Perl.

To install Ruby support, issue the following command:

apt-get install libapache2-mod-ruby

To install Perl support, issue the following command:

apt-get install libapache2-mod-perl2

To install Python support, issue the following command:

apt-get install libapache2-mod-python

If you need support for MySQL in Python, you will also need to install Python MySQL support:

apt-get install python-mysqldb

Your PHP application may require additional dependencies included in Ubuntu. To check for available PHP dependencies run apt-cache search php, which will provide a list of package names and descriptions. To install, issue the following command:

apt-get install libapache2-mod-php5 php5 php-pear php5-xcache

Issue the following command to install the php5-suhosin package, which provides additional security to your PHP installation:

apt-get install php5-suhosin

If you’re also hoping to run PHP with MySQL, then also install MySQL support:

apt-get install php5-mysql

Configure Apache for Named-Based Virtual Hosting

Apache supports both IP-based and name-based virtual hosting, allowing you to host multiple domains on a single server. To begin configuration, edit Apache’s ports.conf file so the NameVirtualHost section resembles the following. Please be sure to replace “12.34.56.78” with your Linode’s IP address.

File: /etc/apache2/ports.conf

1 2	NameVirtualHost 12.34.56.78:80 Listen 80

Next, issue the following command to disable the default Apache virtual host.

a2dissite default

Each additional virtual host needs its own file in the /etc/apache2/sites-available/ directory. In this example, you’ll create files for two name-based virtually hosted sites, “example.com” and “example.com”.

First create example.com (/etc/apache2/sites-available/example.com) so that it resembles the following. Make sure to replace “12.34.56.78” with your Linode’s IP address.

File: /etc/apache2/sites-available/example.com

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<VirtualHost 12.34.56.78:80> ServerAdmin username@example.com ServerName example.com ServerAlias www.example.com DocumentRoot /srv/www/example.com/public_html/ ErrorLog /srv/www/example.com/logs/error.log CustomLog /srv/www/example.com/logs/access.log combined </VirtualHost>

If you would like to enable Perl support, add the following lines to the VirtualHost entry above.

File: /etc/apache2/sites-available/example.com

1 2	Options ExecCGI AddHandler cgi-script .pl

Next, create example.com (/etc/apache2/sites-available/example.com) so that it resembles this:

File: /etc/apache2/sites-available/example.com

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<VirtualHost 12.34.56.78:80> ServerAdmin username@example.com ServerName example.com ServerAlias www.example.com DocumentRoot /srv/www/example.com/public_html/ ErrorLog /srv/www/example.com/logs/error.log CustomLog /srv/www/example.com/logs/access.log combined </VirtualHost>

You’ll note that some basic options are specified for both sites, including where the files for the site will reside (under /srv/www/). You can add (or remove) additional configuration options, such as the Perl support, on a site-by-site basis to these files as your needs dictate.

Create required directories for these sites by issuing the following commands:

mkdir -p /srv/www/example.com/public_html
mkdir /srv/www/example.com/logs

mkdir -p /srv/www/example.com/public_html
mkdir /srv/www/example.com/logs

Enable the sites by issuing these commands:

a2ensite example.com
a2ensite example.com

Finally, restart the Apache server to initialize all the changes, with this command:

/etc/init.d/apache2 restart

When you create or edit any virtual host file, you’ll need to reload the config, which you can do without restarting the server with the following command:

/etc/init.d/apache2 reload

Congratulations! You now have Apache installed on your Ubuntu Linode and have configured the server for virtual hosting.

Install Apache Modules

One of Apache’s prime strengths is its extreme customizability and flexibility. With its support for a large number of modules, there are few web serving tasks that Apache cannot fulfill. By default, modules and their configuration files are installed in the /etc/apache2/mods-available/ directory. Generating a list of this directory will tell you what modules are installed. To enable a module listed in this directory, use the following command:

a2enmod [module-name]

Note that in the /etc/apache2/mods-available/ directory, files have a .load and .conf extension. Module names do not include the extension.

To disable a module that is currently enabled, use the inverse command:

a2dismod [module-name]

To get a list of available Apache modules modules in the Ubuntu repository use the following command:

apt-cache search libapache2*

To install one of these modules use the command:

apt-get install [module-name]

Modules should be enabled and ready to use following installation, though you may have to apply additional configuration options to have access to the modules' functionality. Consult the Apache module documentation for more information regarding the configuration of specific modules.

Configuration Options

One of the strengths, and obstacles, of Apache is the immense amount of flexibility offered in its configuration files. In the default installation of Apache 2 on Ubuntu, the main configuration is located in the /etc/apache2/apache2.conf files, but Apache configuration directives are loaded from files in a number of different locations, in a specific order. Configuration files are read in the following order, with items specified later taking precedence over earlier and potentially conflicting options:

1. /etc/apache2/apache2.conf
2. Files with .load or .conf extensions in /etc/apache2/mods-enabled/ directory.
3. /etc/apache2/httpd.conf (Blank by default.)
4. /etc/apache2/ports.conf
5. Files within the /etc/apache2/conf.d/ directory.
6. Files within the /etc/apache2/sites-enabled/ directory.
7. Per-directory .htaccess files in the directory.

Remember, later files take precedence over earlier-cited files. Within a directory of included configuration files, files will be read in order based on the sort of their file names.

Apache will follow symbolic links to read configuration files, so you can create links in these directories and locations to files that are actually located elsewhere in your file system.

Best practices for most installations dictate that we don’t recommend modifying the following default configuration files: /etc/apache2/httpd.conf, files in /etc/apache2/mods-enabled/, and in most cases /etc/apache2/apache2.conf. This is to avoid unnecessary confusion and unintended conflicts in the future.

Generally, as specified in our LAMP guide for Ubuntu 9.10 (Karmic) and elsewhere, files that configure virtual hosts should be located in the /etc/apache2/sites-available/ directory (and symbolically linked to sites-enabled/ with the a2ensite tool. This allows for a clear and specific per-site configuration.

In practice, the vast majority of configuration options will probably be located in site-specific virtual host configuration files. If you need to set a system-wide configuration option or aren’t using virtual hosting, the best practice is to specify options in files created beneath the conf.d/ directory.

Multi-Processing Module

The default Apache configuration uses a tool called MPM-worker, this multi-processing module can handle a large number of requests quickly by utilizing multiple threads per worker process. However, this use of multiple threads is not compatible with some PHP extensions. When PHP is installed MPM-worker is replaced with MPM-prefork, which allows Apache to handle requests without threading for greater compatibility with some software. Furthermore, using MPM-prefork allows Apache to isolate requests in separate processes so that if one request fails for some reason, other requests will be unaffected.

For more complex setups, however, we recommend that you consider using an alternate MPM module called “ITK.” mpm-itk is quite similar to prefork, but it goes one step further and runs the processes for each site under a distinct user account. This is particularly useful in situations where you’re hosting a number of distinct sites that you need to isolate sites on the basis of user privileges.

Begin by installing the mpm-itk module:

apt-get install apache2-mpm-itk

Now, in the <VirtualHost > entries for your sites (the site-specific files in /etc/apache2/sites-available/) add the following sub-block:

File: Apache Virtual Host Configuration

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<IfModule mpm_itk_module> AssignUserId webeditor webgroup </IfModule>

In this example, webeditor is the name of the user of the specific site in question, and webgroup is the name of the particular group that “owns” the web server related files and processes. Remember that you must create the user accounts and groups using the useradd command.

More Information

You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.

• Apache HTTP Server Version 2.2 Documentation
• Apache Configuration