FTP Delivering Files to Any Client OS

FTP has long been a popular server. The protocol has some peculiarities, but every OS that has a serious TCP/IP stack has an FTP client. FTP is typically used in one or both of two ways:

• Users must authenticate themselves to the server by providing a username and password. They can then read, and often write, files to their home directory or to common areas on the computer.

• Users provide a username of anonymous and any password (conventionally their e-mail addresses). They can then read, but usually not write, data stored in public directories. This anonymous FTP access is a popular means of delivering public files such as software upgrades, multimedia files, and so on.

Both configurations share many features, but certain details differ. How you set up an FTP server to use either system depends on the server you choose. Several such servers exist for Linux. This section describes your choices and then covers two popular FTP servers, ProFTPd and vsftpd, in more detail.

Warning One of FTP'S major problems when used for authenticated user access is that FTP sends all data, including passwords, in an unencrypted form. This fact means that miscreants on the server's network, the client's network, or intervening networks can use packet sniffers to steal users' passwords. This issue isn't as much of a problem for anonymous access, which is supposed to be public.

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