Adding support for new users cannot be done using the last method

[FranEva]

Adding support for new users cannot be done using the last method, because your initialization script run-vsftpd.sh contains the line echo -e "${FTP_USER}\n${FTP_PASS}" > /etc/vsftpd/virtual_users.txt. Once the Docker container is restarted, it will restore virtual_users.txt.

My understanding is that you need to modify the script to something like echo -e "${FTP_USER1}\n${FTP_PASS1}\n${FTP_USER2}\n${FTP_PASS2}\n${FTP_USER3}\n${FTP_PASS3}" > /etc/vsftpd/virtual_users.txt. I have already tested this locally.

If you really need to execute it inside the container, after execution you need to use docker commit to create a new container, but this approach seems to be against the specifications and the original design intent.