Debian 10: How can I disable nftables and continue to use IPTables only?

Solution 1:

At least for Debian 10 this should work:

update-alternatives --set iptables /usr/sbin/iptables-legacy
update-alternatives --set ip6tables /usr/sbin/ip6tables-legacy
update-alternatives --set arptables /usr/sbin/arptables-legacy
update-alternatives --set ebtables /usr/sbin/ebtables-legacy

See also: https://wiki.debian.org/nftables

Solution 2:

For anyone who might find this, I tried the solution above, but had a further issue after running update-alternatives where I got this error:

update-alternatives: error: alternative /usr/sbin/iptables-legacy for iptables not registered; not setting

The solution was to manually add it as an alternative:

sudo update-alternatives \
--install /usr/sbin/iptables iptables /usr/sbin/iptables-legacy 10 \
--slave /usr/sbin/iptables-restore iptables-restore /usr/sbin/iptables-legacy-restore \
--slave /usr/sbin/iptables-save iptables-save /usr/sbin/iptables-legacy-save