Once I noticed the following error in the file /var/log/proftpd/proftpd.log:
error: unable to open passwd file ‘/etc/proftpd/ftpd.passwd’: Permission denied
As it turned out, the rights to the file were 440 and the owner and group were specified as root
Let’s look in the file /etc/proftpd/proftpd.conf, from which user ProFTPd works, by default from the user proftpd:
User proftpd
Group nogroup
Just in case, we will specify the correct rights to the files (if they are other, then ProFTPd may not start):
sudo chmod 440 /etc/proftpd/ftpd.passwd
sudo chmod 440 /etc/proftpd/ftpd.group
And we will point to the owner files under which ProFTPd is running (for example, by default from proftpd, we leave the group as root):
sudo chown proftpd.root /etc/proftpd/ftpd.group
sudo chown proftpd.root /etc/proftpd/ftpd.passwd
If necessary, restart ProFTPd:
sudo service proftpd restart
After that, you can connect to ProFTPd, there should be no errors.
See also my article:
Configuring ProFTPd with virtual users in a file
It Works! Thank You!