vsftpd giving error [500 OOPS: child died] instead of [421 Timeout] – after idle_session_timeout

[500 OOPS: child died] is a permanent negative error reply, whereas [421 Timeout] is a temporary negative error reply.

• Downgrade vsftpd to a lower version to resolve this issue.

Check vsftpd man pages for details on Transient Negative Completion reply and Permanent Negative Completion reply.