The world wide web runs on a protocol known as http or the hypertext transport protocol. This was first developed by Tim Berners-Lee in 1989. His initial idea was to provide a mechanism of linking similar information from disparate sources. Similar in concept to the way your mind might work. Http is the protocol that is the most utilized on the Internet today. It is still part of the TCP/IP protocol stack, just the same as SMTP, ICMP and others, but's it's responsibility is transferring data (web pages) around the Internet.
Apache comes in two basic flavors: Apache version 1.3.x and version 2.x. Since the configuration of these two differ quite substantially in some places, we will focus this course on the configuration of version 2. Should you still be running version 1.3, we suggest you upgrade. You'll need to do it at some point, so the sooner the better (IMHO). If you can't, most of this course will apply to you, but your mileage may vary somewhat.
The Apache web server has been designed to be used in either a modular or non-modular way. In the former, modules are compiled separately from the core Apache server, and loaded dynamically as they are needed. This, as you can imagine, is very useful as it keeps the core software to a minimum, thereby using less operating system resources. The downsides of course are that the initial startup of the server is a little slower, and the overhead in loading a module adds to the latency in offering web pages. The latter means of compiling Apache is to include all the "modules" in the core code. This means that Apache has a bigger "footprint", but the latency overhead is down to the bare minimum. Which means you use is based upon personal choice and load on you web server. Generally though, when you unpack an Apache that has been pre-compiled (i.e. It's already in a .deb or .rpm package format), it is compiled to be modular. This is how we'll use it for this course.
The core Apache server is configured using one text configuration file - httpd.conf. This usually resides in /etc/httpd, but may be elsewhere depending on your distribution. The httpd.conf file is fairly well documented, however there are additional documentation with Apache that is an excellent resource to keep handy.
The server has 3 sections to the configuration file:
The global configuration settings
The main server configuration settings
The virtual hosts
In this part of the configuration file, the settings affect the overall operation of the server. Setting such as the minimum number of servers to start, the maximum number of servers to start, the server root directory and what port to listen on for http requests (the default port is 80, although you may make this whatever you wish).
The majority of the server configuration happens within this section of the file. This is where we specify the DocumentRoot, the place we put our web pages that we want served to the public. This is where permissions for accessing the directories are defined and where authentication is configured.
Hosting of many sites does not require many servers. Apache has the ability to divide it's time by offering web pages for different web sites. The web site www.QEDux.co.za, is hosted on the same web server as www.hamishwhittal.org.za. Apache is operating as a virtual host - it's offering two sites from a single server. We'' configure some virtual hosts later in the course.