FTP connection to the server cannot be established. FTP client returns the error:
421 Service not available, remote server has closed connection
The following error message is seen in the /var/log/messages log file:
getaddrinfo 'Hostname\_Is\_Here' error: Name or service not known warning: unable to determine IP address of 'host.domain.tld domain'
This problem happens because FTP server is unable to determine the IP address of the server by hostname. Check it with the following command:
Define correct hostname in the configuration files below and restart network service.
The following example shows how to set up hostname "hostname.domain.tld" on RedHat systems.
127.0.0.1 localhost localhost.localdomain
18.104.22.168 hostname.domain.tld hostname
# /etc/init.d/network restart
Where "22.214.171.124" and "hostname.domain.tld" have to be replaced with the real server IP and hostname accordingly.
Also, in the latest Parallels Plesk Panel versions hostname can be set through Plesk CP on the Server->Preferences page.