I've disabled IPv6 on a set of Docker nodes following the instructions from Disabling IPv6 in Ubuntu Server 18.04. However, netfilter-persistent is still complaining about IPv6:
root@docker10:~# netfilter-persistent save
run-parts: executing /usr/share/netfilter-persistent/plugins.d/15-ip4tables save
run-parts: executing /usr/share/netfilter-persistent/plugins.d/25-ip6tables save
ip6tables-save v1.6.1: Cannot initialize: Address family not supported by protocol
run-parts: /usr/share/netfilter-persistent/plugins.d/25-ip6tables exited with return code 1
root@docker10:~#
How can I stop this from happening? It's leading to Puppet errors in the logs, and other noise.
The following commands confirm that IPv6 is disabled:
root@docker10:~# grep ipv6 /etc/default/grub
GRUB_CMDLINE_LINUX="ipv6.disable=1"
root@docker10:~# ls /proc/net/if_inet6
ls: cannot access '/proc/net/if_inet6': No such file or directory
root@docker10:~# ip address | grep inet6
root@docker10:~# sysctl -a |grep ipv6
root@docker10:~#
