Sorry, I hadn't read the top of "/etc/services". I'd simply grepped for 20048.
20048 has been IANA's mountd port since 2010 or 2011. Having that line included means that "rpc.mountd" uses that port and someone seting up nfs can configure iptables without having to define a random fixed port. Debian and Slackware recommend 32767 (which is assigned by IANA to some obscure thing). Furthermore, if you use firewalld and run "firewall-cmd [--permanent] --add-service=mountd", port 20048'll be opened in your firewall, as can be seen in "/usr/lib/firewalld/services/mountd.xml". ufw also uses "services" but I don't know whether it defines a mountd one. Thanks
