In either case, you will need to install the web server using APT.

For Apache:

apt-get install task-web-server #

For Nginx:

apt-get install nginx #

If you install Apache, you will note there are several flavors of it available as different packages; worker is one of the MPMs (Multi Processing Module) for Apache. You might also want to use prefork since it provides a similar operation model to previous versions of Apache and avoids threads, which might be a problem with non-thread-safe libraries. Simply write apt-get install task-web-server apache2-mpm-prefork+ (think of the plus sign as "I really want this package").

There are two steps for configuring your web server: configure your site or virtual host, and configure your application execution method.

Configuring virtual hosts is very easy in both Apache and Nginx. They both have sites-available folders (under /etc/apache2 and /etc/nginx respectively) where you can drop in a bit of configuration corresponding to your host. You can then link that file to the sites-enabled/ folder (or, for Apache, using the a2ensite/a2dissite tool) and reload your server.

For Apache:

service apache2 restart #

For Nginx:

service nginx restart #

Configuring the execution method for your application depends on the programming language you are using (Perl, Python, PHP, Ruby, and so on). We'll assume PHP. As previously mentioned, while Nginx will run PHP via FastCGI, Apache also offers the possibility of using mod_php, where PHP is basically embedded in the Apache process. For doing that, you only need to install and enable the mod_php module:

apt-get install libapache2-mod-php5

For Nginx, the easiest configuration involves spawning a PHP FastCGI process (manually or optionally with an init script) and setting FastCGI parameters, as described on the Nginx Wiki page (http://wiki.nginx.org/PHPFcgiExample). Here, you can find lots of other configuration snippets, including advanced proxying, caching, and specific directives for CMS and other programming languages besides PHP.

Separating the database from the application server may also make sense since the database is I/O bound but the web application is not—most of the time. But you might not have much hardware, or you might be planning on scaling out with tight application plus database units in volumes. Or you might not be using a conventional database at all. However, let's assume you are.

As with the application server, there are two schools for RDBMS: MySQL and PostgreSQL. Debian's default is PostgreSQL but you're free to choose.

apt-get install mysql-server

OR

apt-get install postgresql

Configuration involves lots of variables, from performance to security, and while the default configuration works fine for setting up your server, we will provide some pointers later in the book.

Finally, you need to install the proper bindings for the programming language you're using; otherwise, the application will not be able to connect to the database. For example:

apt-get install php5-mysql

Most likely, the interpreter for your language is already installed on Debian (such as Perl, Python) or is readily available (such as PHP through mod_php, or Ruby, and so on) but some libraries might not be. For example, if your application needs gd extensions, you can perform:

apt-get install php5-gd