In the last chapter, you learned how to connect your Linux system to a local-area network or, via an Internet Service Provider, to the Internet. By doing so, you were able to access a plethora of services provided by others, including file transfers via FTP, web pages, email, and telnet. In this chapter you’ll learn how to set up several Linux wide-area network servers, including an FTP server, a web server (Apache), an email (SMTP/POP) server, and a dial-in shell server. These applications let you and others access data on your Linux system from anywhere in the world via the Internet. These applications will be most useful if your system is connected to the Internet 24 hours a day, 7 days a week. But, even if your connection is intermittent, you and others can access the services these applications provide whenever the connection is active.
An FTP server lets you transfer files from one system to another, via a network. When two computers are connected to the Internet, you can use FTP to transfer files from one to the other even though the computers are not directly connected.
An FTP server attempts to authenticate users that request to use it. You can configure your FTP server to accept requests only from users who have an account on the system running the FTP server. Alternatively, you can configure the FTP server to accept requests from anyone, via a facility known as anonymous FTP