Apache is an open source widely used Web Server application. Apache runs on nearly all flavours of Unix (and Linux), Windows, BeOs, mainframes...It is a software that runs in the background under an appropriate operating system, which supports multi-tasking, and provides services to other applications that connect to it, such as client web browsers.
Installing Apache on Linux does require a bit of programming skill. Installing it on a Windows platform is straightforward, as you can run it through a graphical user interface. To add a new module, all you need to do is install it and restart the Apache server. The Apache server also supports third-party modules. The Apache server very easily integrates with other open source applications, such as PHP and MySQL
The Apache server offers a number of services that clients might make use of. These services are offered using various protocols through different ports. It includes hypertext transfer protocol (HTTP), typically through port 80, simple mail transfer protocol (SMTP), typically through port 25, domain name service (DNS) for mapping domain names to their corresponding IP addresses, generally through port 53, and file transfer protocol (FTP) for uploading and downloading files, usually through port 21.
Apache's main role is all about communication over networks, and it uses the TCP/IP protocol. It is set up to run through configuration files, in which directives are added to control its behaviour. Whenever it receives a request, it analyzes the headers, applies the rules specified for it in the Config file, and takes action.
Apache can be installed on a variety of operating systems.
htdocs is the default Apache web server document directory, it is the public directory whose contents are usually available for clients connecting through the web.It contains all static pages and dynamic content to be served once an HTTP request for them is received.
conf is the directory where all server configuration files are located. Configuration files are basically plain text files where directives are added to control the web server's behaviour and functionality. Each directive is usually placed on a separate line, and the hash (#) key indicates a comment so the line proceeded by it is ignored.
logs is the directory where server logs are kept and include Apache access logs and error logs. The Apache HTTP Server provides a variety of different mechanisms for logging everything that happens on it, from the initial request, through the URL mapping process, to the final resolution of the connection, including any errors that may have occurred in the process.
cgi-bin is the directory where CGI scripts are kept. The CGI (Common Gateway Interface) defines a way for a web server to interact with external content-generating programs, which are often referred to as CGI programs or CGI scripts.
The following websites use Apache or derivatives
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