Disabling IPv4 on the Raspberry Pi / 2016-11-12

I have two Raspberry Pi's running in the house, currently with IPv4 still enabled on them. They both run Raspbian 8.0. I was wondering whether I can disable IPv4 on the Raspberry Pi, but a google search does not yield very helpful answers, most of the search terms I try still find pages about disabling IPv6. I want to disable the legacy IP protocol.

Only one way to find out: go for it. Now rebooting one with the statement ipv6only in /etc/dhcpcd.conf.

First thing I noticed was that the searchdomain was not set in /etc/resolv.conf which was indeed only available via the DHCP process for IPv4. So now radvd advertises the search domain via the DNSSL option in /etc/radvd.conf:

   RDNSS 2001:980:14ca:42::18 {
   };
   DNSSL idefix.net {
   };

The first results are:

• It turned out the ntp config on the raspberry had one IPv6-only and one IPv4-only server. Added a dual-stack server.
• And ndpmon really does not like the DNSSL option, even when I add it in the config_ndpmon.xml file as

                    <dnssl>
                      <domain lifetime="600">idefix.net</domain>
                    </dnssl>
  

  Fixed by changing it to

                    <dnssl>
                      <domain lifetime="600">^Fidefix^Cnet</domain>
                    </dnssl>
  

  yes, with literal ctrl-F and ctrl-C characters, showing that there is some error in the parsing somewhere.
• rwhod is IPv4-only so the status is not visible in my network anymore. A workaround for that is not disabling IPv4 completely but just removing the default route, not using ipv6only in /etc/dhcpcd.conf but using the option nooption routers.