Firewalld Default Backend Change from iptables to nftables

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Environment

SUSE Linux Enterprise Server 15 SP3

Situation

As of SLES 15 SP3, the default backend for firewalld has changed from iptables to nftables:
https://www.suse.com/releasenotes/x86_64/SUSE-SLES/15-SP3/index.html#jsc-SLE-16300

Resolution

The default backend for firewalld is now nftables. There are a few options for mitigating disruption during the transition.

The iptables-nft utility

The "iptables-nft" command can be used to run the iptables equivalent commands while using the nftables API.

Change Default Backend

If necessary the backend can be switched back to iptables with the "FirewallBackend" value in the "/etc/firewalld/firewalld.conf":

FirewallBackend=iptables

Restart the service after modifying the configuration file to make the change:

systemctl restart firewalld

Cause

The upstream firewalld has been focusing its backend development on nftables due to several reasons that are explained here:
https://firewalld.org/2018/07/nftables-backend

Disclaimer

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