What is it?
The Apache HTTP web server has lost a great deal of market share to Microsoft's IIS in the last couple of years. But since its share once amounted to almost 80 per cent of the market, a readjustment was perhaps inevitable.
In recent months, Apache's fall and IIS's growth both seem to have levelled out, giving Apache just over 50 per cent, and IIS just under 36 per cent. These figures come from Netcraft, which looks at absolute numbers, regardless of the size of the site. A survey of the "top 100" US sites gives Apache 49 per cent, and IIS 20 per cent.
The Apache Software Foundation describes its HTTP Server Project as "a collaborative software development effort aimed at creating a robust, commercial-grade, featureful, and freely available source code implementation of an HTTP (web) server", protecting the protocols of the web from proprietary ownership. The open source, free-to-download web server has also achieved wide success among commercial vendors: it is bundled by the likes of IBM and Oracle, as well as with most Linux distributions.
Where did it originate?
Apache was put together from the many patches supplied by different hands for the public domain HTTP daemon (httpd) developed at the National Center for Supercomputing Applications, University of Illinois. Apache 1.0 was released in 1995, and grew as the web grew. The Apache Software Foundation was established in 1999, and is now responsible for more than 30 projects, including the Struts open source Java application framework, and the Tomcat servlet container.
What's it for?
Apache is the web server component of the Lamp stack, along with Linux, MySGL or Postgres, and PHP, Python or Perl. But it's also used with LAMP equivalents based on Windows, and on Sun's Solaris, and is supplied with Mac OSX. Apache has moved a long way from simply serving static and dynamic web pages, with authentication and cryptography, and support for scripting languages.
What makes it special?
Although Apache is constantly evolving by way of regular bug-fix and security releases, it's been remarkably stable, with just two major versions since 1995. While champions tend to exaggerate its security record (it's just as vulnerable to sloppy configuration and administration), it hasn't suffered the widespread and high profile problems that have sometimes followed releases of IIS.
How difficult is it to master?
Not for the faint-hearted. The tutorial material on the apache.org site requires you to download the software and get stuck in, and as a result, many posts about Apache are from would-be beginners seeking guidance. Much of this "official" material is also years out of date. But there are plenty of independent sites offering tutorials and support.
What systems does it run on?
Unix, Linux, Windows, Mac OSX, Netware and others.
Rates of pay
Linux and Apache systems administrators start at around £25k and can look for up to £45k with two years' experience.
For downloads and tutorials, begin at apache.org.
There are links to friendlier external tutorials here.
Most tutorials plunge you straight in without an overview there are plenty of books providing a gentler introduction, though Amazon is a better place to start than the out-of-date list on the Apache site.