ProFTPD Virtual User Setup with AuthUserFile

1. Edit or add following to proftpd.conf
   
   AuthOrder mod_auth_file.c
   AuthUserFile /etc/proftpd/ftpd.passwd
   AuthGroupFile /etc/proftpd/ftpd.group
   RequireValidShell off
2. Get uid and gid
   
   cat /etc/passwd | grep <username>
   cat /etc/group | grep <groupname>
3. Add users to ftpd.passwd
   
   ftpasswd --uid <uid> --gid <gid> --gecos "Full Name" --name <username> --shell /bin/false --home <path> --passwd
4. Add Groups to ftpd.group
   
   ftpasswd --gid <gid> --name <groupname> --group
   
5. Add members to a group
   
   ftpasswd --gid <gid> --name <groupname> --member <membername> --group
6. Set permissions on the ftpd.passwd and ftpd.group files
   
   chmod 400 /etc/proftpd/ftpd.passwd /etc/proftpd/ftpd.group
   chown proftpd.nogroup /etc/proftpd/ftpd.passwd /etc/proftpd/ftpd.group
7. Restart ProFTPD
   
   /etc/init.d/proftpd restart

[ Reference(s): Link1, Link2 ]