What does pasv_enable and related fields mean in vsftpd.conf

Question

I just installed vsftpd according to these directions.

I am trying to get ftp working on my Ubuntu box that is using Amazon AWS. When I first tried this directions, it did not work. I was trying to connect via FileZilla and Winscp from my windows machine to my Ubuntu server.

When it failed, I tried adding these options to my /etc/vsftpd.conf file. Specifically:

pasv_enable=YES
pasv_min_port=64000
pasv_max_port=64321
port_enable=YES
pasv_address=<your-publicly-resolvable-host-name>
pasv_addr_resolve=YES <or> NO

This did not help. Finally, what did work was switching winSCP into "Active Mode". My question is: What do those different parameters mean? I am assuming that in is to enable passive mode, and to help guide the ports used for passive mode, but I am not sure what port_enable pasv_address and pasv_addr_resolve do.

Also, now that I am using active mode, do I need to have any of those entries? Thank you

Solution

There is (obviously) manual page for vsftpd.conf, which is always a good place to start.

TLDR version: They should be needed only for passive mode of FTP.

pasv_enable

Set to NO if you want to disallow the PASV method of obtaining a data connection.

Default: YES

---

pasv_address

Use this option to override the IP address that vsftpd will advertise in response to the PASV command. Provide a numeric IP address, unless pasv_addr_resolve is enabled, in which case you can provide a hostname which will be DNS resolved for you at startup.

Default: (none - the address is taken from the incoming connected socket)

---

pasv_addr_resolve

Set to YES if you want to use a hostname (as opposed to IP address) in the pasv_address option.

Default: NO