Problems with nsd4 after disabling IPv6

Hi there!

I was migrating my MiaB setup from one vServer to another and spent some hours to finde out the problem why the nsd4 process do not wanted to start. Every time I had the following error:
Public DNS (nsd4) is not running (port 53).

The problem was that I wanted to disable IPv6 (as it is not recommended for now, right?) and added some lines to the /etc/sysctl.conf file. With my first VPS it was not a problem: there I was able to disable IPv6 from the control panel.

Now I have 2 questions:

  1. Is it no problem that my VPS has an “unused” IPv6 because of security aspects or should I try to contact my hosting provider and ask to disable it?
  2. Why the disabling of IPv6 on Ubuntu did not work and “ruined” my whole MiaB setup?
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In the meantime I asked my hosting provider to disable IPv6, but it’s something that is not provided. So what would be the best solution to disable IPv6 and not to break my MiaB setup?

Bumping this topic, because, after much procrastination, I finally decided to upgrade from MIAB 0.30/Unbuntu 14.04, which requires a new install of Ubuntu 18.04 and encountered the same issue: nsd4 would not start because IPv6 was disabled

In my case, my VPS provider’s (Contabo) OS Re-install feature actually disables IPv6 by default, without letting me know.

I was very lucky to come across this old, but precious post and commented out the line below in my /etc/sysctl.conf file which fixed the issue:

#net.ipv6.conf.all.disable_ipv6 = 1

Obviously, as with the original poster, I would really like to understand why disabling IPv6 prevents nsd4 from starting.