500 OOPS: cannot open config file:/etc/vsftpd/vsftpd.conf

It is problem about file's owner. U should set correct owner for config /etc/vsftpd/vsftpd.conf

sudo chown root /etc/vsftpd/vsftpd.conf

Depending on the OS, you may get the following error because of the incorrect command being run. For example, I ran the following command in Linux Mint 15:

sudo vsftpd restart

The output I received was:

500 OOPS: cannot read config file: restart

The correct command to restart vsftpd daemon was:

sudo restart vsftpd 

This gave the output:

vsftpd start/running, process 2231

Use service vsftpd [start/restart/stop], not simply vsftpd [start/restart/stop]

My solution was to start vsftpd with the systemctl command.

sudo systemctl start vsftpd