Proftpd error: fatal: Socket operation on non-socket

Error

root@hostname [~]# /etc/init.d/proftpd restart
Stopping proftpd: [FAILED]
Starting proftpd: hostname.domainname.com – fatal: Socket operation on non-socket
[FAILED]

Reason

The ProFtpd was configured to run in “inetd” mode. In “inetd” mode, ProFTPD expects that it will be run from the inetd super-server, which implies that stdin/stdout will be sockets instead of terminals. As a result, socket operations will fail.

root@hostname [~]# grep ServerType /etc/proftpd.conf

ServerType                      inetd

root@hostname [~]#

Fix

Edit the proftpd configuration and  change the ServerType to “standalone” mode and restarted ProFtpd.

root@hostname [~]# grep ServerType /etc/proftpd.conf
ServerType                      standalone
#ServerType                      inetd
root@hostname [~]#    /etc/init.d/proftpd restart
Stopping proftpd:                                          [FAILED]
Starting proftpd:                                          [  OK  ]

For more details : http://www.proftpd.org/docs/faq/linked/faq-ch4.html