Correção do ERRO:
root@ok:~# csf
*Error* The path to iptables is either not set or incorrect for IPTABLES [/usr/sbin/ip6tables] in /etc/csf/csf.conf at /usr/local/csf/lib/ConfigServer/URLGet.pm line 26.
Compilation failed in require at /usr/sbin/csf line 21.
BEGIN failed--compilation aborted at /usr/sbin/csf line 21.Isso ocorre porque o caminho para o iptables foi alterado no Ubuntu 20.04. Para corrigir o erro edite csf.conf
vi /etc/csf/csf.confLocalize:
IPTABLES = "/sbin/iptables"
IPTABLES_SAVE = "/sbin/iptables-save"
IPTABLES_RESTORE = "/sbin/iptables-restore"
IP6TABLES = "/sbin/ip6tables"
IP6TABLES_SAVE = "/sbin/ip6tables-save"
IP6TABLES_RESTORE = "/sbin/ip6tables-restore"Substitua por:
IPTABLES = "/sbin/iptables"
IPTABLES_SAVE = "/sbin/iptables-save"
IPTABLES_RESTORE = "/sbin/iptables-restore"
IP6TABLES = "/sbin/ip6tables"
IP6TABLES_SAVE = "/sbin/ip6tables-save"
IP6TABLES_RESTORE = "/sbin/ip6tables-restore"Reiniciei o CSF
csf -r