I setup virtual users on my Ubuntu server and had login errors trying to login. I repeated the steps like a zillion times to see the same login error.
331 Password required for somevirtualuser Password: 530 Login incorrect. ftp: Login failed
Finally, I tried to see the services running using:
sudo netstat -ltp | grep ftp
and, saw a proftpd process running.
rizwan@dragonstone:~$ sudo netstat -ltp|grep ftp tcp6 0 0 [::]:ftp [::]:* LISTEN 27137/proftpd: (acc
Lesson: Always check processes running before tampering with config files.
This is more like a noob tip than a pro tip