Update：upgrade Ubuntu 20.04 LTS Rear，csf is not working，Prompt that iptables cannot be found：
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Testing ip_tables/iptable_filter...open3: exec of /sbin/iptables -I OUTPUT -p tcp --dport 9999 -j ACCEPT failed: No such file or directory at /usr/local/csf/bin/csftest.pl line 144. |
This is because Ubuntu 20.04 LTS Changed iptables Related command position，The csf script is not updated in time。[……]