How To Configure ProFTPd To Use SFTP Instead of FTP https://www.digitalocean.com/community/tutorials/how-to-configure-proftpd-to-use-sftp-instead-of-ftp
WordPress Support ยป Unable to locate WordPress Content directory (wp-content). http://wordpress.org/support/topic/unable-to-locate-wordpress-content-directory-wp-content
How to Stop WordPress Asking for FTP details to Upgrade Plugins http://www.gravitationalfx.com/how-to-stop-wordpress-asking-for-ftp-details-to-upgrade-plugins/
Putting FTP Info in wp-config.php to Ease Updates | Digging into WordPress http://digwp.com/2010/11/ftp-in-wpconfig/