Plesk 12.x / Linux :: Configuration Of FTPS With TLS And FTP Backup Repository

Plesk Panel 12 uses a proftpd FTP server, with the TLS module pre-installed and configured.

Many questions and/or problems arise when trying to connect to the FTP server over a FTPS connection. In (almost) all cases, the disability to connect with FTPS is due to

a) the lack of configuration of passive ports, AND
b) firewall settings, enabling connections through before mentioned passive ports.

The passive port range can be configured by

adding a line to /etc/proftpd.conf, stating: "PassivePorts <start> <end>", OR
adding a separate file with name <filename>.conf to /etc/proftpd.d/, with the contents of <filename>.conf stating: "PassivePorts <start> <end>"

And note that

- <start> is the first port of the port range, in theory any value above 1050 can suffice,
- <end> is the last port of the port range, any value below 65000 (!) can suffice,
- the extension .conf is required when using a separate config file,
- the directory location /etc/proftpd.d/ is required when using a separate config file,
- one should always limit the port range, i.e. it is not desirable to open up a lot of ports,
- it is desirable to have the <start> value above 20000, in order to prevent conflicts with other programs, using a specific port (for instance, port 8443 is also being used),
- it is not necessary to restart proftpd after configuring the passive ports. ​

The firewall settings have to be changed to allow connections through the passive ports that have been opened for FTPS connections and note that

- only open up the port range (not more) in the firewall settings,
- it is only necessary to open up ports in the firewall settings of the FTP server,
- it is not required to open up ports in the firewall settings of the sending server.
​
Many issues have been arising when setting up the FTP Backup Repository.

In general, the passive mode checkbox has to be selected, when encountering issues.

The explicit use of the passive mode allows for proper configuration of the FTP Backup Repository and note that it does not matter whether FTPS or normal FTP will be used.