FTP server

FTP server lets users upload and download files and directories.
The FTP daemon is named /usr/sbin/in.ftpd.
Three levels of FTP access are provided:
1.User access, access by users who have a login account on the server host.
2.Guest access, access by users who have a special guest account that
provides only FTP access.
3.Anonymous access, access by users who have no defined account on the
server host.

FTP server is distributed as two packages:
1. wu-ftpd, which contains the FTP server
2. nonftp, which contains the anonymous FTP server

The FTP service has three basic configuration files:
1. /etc/ftpaccess, which specifies global options and user permissions
2. /etc/ftphosts, which specifies client hosts that may or may not
access the FTP service
3. /etc/ftpusers, which specifies users who may not access the FTP service.

By default, the FTP service is run as an inetd service. Thus, it is not necessary
to start, restart, or stop the service.