Is it possible to install with IPv6 disabled? (Spoiler: I don't think so)

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In a discussion titled ‘Is it possible to install with IPv6 disabled? (Spoiler: I don’t think so)’, pfaffman reports attempting to disable IPv6 in Discourse by modifying nginx config files to remove or alter [::]:80 listeners, but still encounters errors like socket() [::]:80 failed (97: Address family not supported by protocol). They reference an old post by Falco indicating nginx fails to boot when IPv6 is disabled at the kernel level. featheredtoast confirms it’s unlikely to work, noting IPv6 is deeply integrated into Discourse’s package, making clean removal difficult and unsupported. pfaffman thanks them, relieved no simple fix was overlooked. The motivation stems from a VM provider disabling IPv6, which took months to resolve. The consensus is that running Discourse without IPv6 is currently not feasible due to hard-coded dependencies in nginx and other components.

1

I see in the web template where it checks to see if /proc/net/if_inet6 exists and turns off the listen for [::]:80, but there’s still one in the default nginx file.

I added these to try to fix that:

  - exec: sed -i '/listen \[::\]:80 default_server;/d' /etc/nginx/sites-available/default
  - exec: sed -i 's/listen 80 default_server;/listen 0.0.0.0:80 default_server ipv6only=off;/' /etc/nginx/sites-available/default
  - exec: sed -i 's/listen 80 default_server;/listen 0.0.0.0:80 default_server ipv6only=off;/' /etc/nginx/conf.d/discourse.conf

But I still see this in the logs:

2025/09/02 21:34:29 [emerg] 359#359: socket() [::]:80 failed (97: Address family not supported by protocol)
2025/09/02 21:34:34 [notice] 3240#3240: signal process started
2025/09/02 21:34:34 [error] 3240#3240: open() "/run/nginx.pid" failed (2: No such file or directory)

A long time ago, it seemed impossible:

Has anyone actually made Discourse work with IPv6 disabled at the kernel level?

(Why? Because the VM someone supplied has IPv6 turned off. It took months for them to provision a VM that they would let me access.)

2

Doubtful. I’ve also recently removed a similar line in the ssl file recently with some eyes by @schleifer - just hadn’t gotten to the web template yet.

IPv6 support is pretty baked into our package, so it’s fairly difficult to rip out cleanly everywhere, and provide verification/support for it.

3

Thanks so much for the quick confirmation! I was pretty sure that was the case, and am relieved that I hadn’t overlooked some obvious simple solution.