FTP and TFTP services are useful for quick file transfers or firmware upgrades for network appliances such as router, switch, access points, etc. These services are disabled by default because FTP and TFTP services by no means should be used for general file transfers. If you want to transfer files in regular bases, you should consider using SFTP or SCP since they are encrypted and your password is not sent in a clear-text format.
To enable FTP, you can type the following command in Lion’s terminal
sudo -s launchctl load -w /System/Library/LaunchDaemons/ftp.plist
To enable TFTP:
sudo -s launchctl load -w /System/Library/LaunchDaemons/tftp.plist
and to remove them, it is as simply as using the “unload” variable in the launchctl command:
sudo -s launchctl unload -w /System/Library/LaunchDaemons/ftp.plist
sudo -s launchctl unload -w /System/Library/LaunchDaemons/tftp.plist
Keep in mind that you need to use the user account on the Lion machine to login to FTP to gain the access to the files. As for TFTP, you should put the files under /private/tftpboot so your TFTP client can access the files.