![]() No need for further granularity in this use case. In order to simplify the setup, I checked what was the default zone, added the network interface adapter to it and defined the needed rules there. Each one can have different sets of rules. In summary, what one needs to understand is that there are multiple “zones” within firewalld. I won’t repeat what multiple other sources say, so I suggest this Digital Ocean article that explains firewalld concepts, like zones and rules persistency. Before doing any changes, I tried to familiarize myself with the basic commands. After installing it, I went for the simplest goal ever: block all incoming connections while allowing SSH (and preferably Mosh, if possible). This should not be the case on future releases. Based on these credentials, I took the advice knowing it came from someone who knows what they are doing.Ī fun fact is that the iptables package is actually a dependency for firewalld on Debian Bullseye. I never met the author while actively working on Debian, but I do know he’s the maintainer of multiple firewall-related packages in the distribution and also works on the netfilter project itself. The article ends up suggesting that firewalld is supposed to be the default firewall rules wrapper/manager - something that is news to me. While looking for some guidance on what are the best practices to manage firewall rules these days, I found the article “ What to expect in Debian 11 Bullseye for nftables/iptables”, which explains the situation in a straightforward way. I scratched my head a bit wondering if the day I would be obliged to learn how to use nftables had finally came. I am running the following linux distribution on my machine: Debian firewall I have installed OpManager on the other machine and wish to configure SNMP. While it’s known for at least 5 years that this was going to happen, it still took me some time to let the idea of its deprecation sink and actually digest the situation. It’s easy to imagine how big was my surprise when I found out that the iptables command wasn’t available. If you face any problem or any feedback, please leave a comment below.After doing a clean Debian 11 (Bullseye) installation on a new machine, the next step after installing basic CLI tools and disabling SSH root/password logins was to configure its firewall. Now you have learned how to secure your server by installing and configuring CSF in Debian 11. Sudo csf -d 10.0.2.12 Remove IP from allow list sudo csf -ar 10.0.2.12 Remove IP from deny list sudo csf -dr 10.0.2.12 Check if IP is blocked sudo csf -g IP-ADDRESS Remove IP from block sudo css -tr IP-ADDRESS Allow IP listsĪdd your IPs listed on a separate line in the allow file /etc/csf/csf.allow.Īdd your IPs listed on a separate line in the allow file /etc/csf/csf.deny. You must restart CSF each time the configuration file changes. Sudo csf -ra Essential Commands to Manage CSF Start CSF sudo csf -s Stop CSF sudo csf -f Restart CSF I have added the MYSQL port to connect to a remote server. Locate the TCP_IN directive and add your ports. Hit CTRL+X followed by Y and ENTER to save and exit the file. This means only members of the RESTRICT_SYSLOG_GROUP may access syslog/rsyslog files. Locate the line RESTRICT_SYSLOG = “0”, and change the value to “3”. ![]() Locate the line TESTING = “1”, and change the value to “0”. To disable TESTING mode you need to make changes to the /etc/csf/csf.conf file. Once the firewall is installed it is configured to run in TESTING mode by default. *WARNING* TESTING mode is enabled - do not forget to disable it in the configuration Configure CSF You can check the CSF version using the following command. RESULT: csf should function on this server You will receive an output similar to the one below. Verify if the required iptables modules are present. Now you will receive an output as below which indicates the successful installation.
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