Fail2ban extension hangs in Plesk | How to resolve

Fail2ban extension hangs in Plesk and causing trouble? Read to find out how to go around it. 

At Bobcares, we offer solutions for every query, big and small, as a part of our Server Management Service.

Let’s take a look at how our Support Team is ready to help customers when Fail2ban extension hangs in Plesk.

All About Fail2ban extension hangs error in Plesk

Fail2Ban protects computer servers from brute-force attacks. It is an intrusion prevention software framework that offers self-regulating security. Although it offers additional security to your servers, it is still prone to errors. The “ Fail2ban extension hangs” error is one such example.

This specific error results in deleting Fail2Ban chains in iptables when we attempt to disable Plesk Firewall via Tools and Settings > Firewall.

We will also notice the following error messages in the /var/log/fail2ban.log file:

CONFIG_TEXT: fail2ban.actions        [13400]: ERROR   Failed to stop jail 'plesk-wordpress-j' action 'iptables-multiport': Error stopping action
fail2ban.jail           [13400]: INFO    Jail 'plesk-wordpress-j' stopped
fail2ban.action         [13400]: ERROR   iptables -D INPUT -p tcp -m multiport --dports http,https,7080,7081 -j f2b-plesk-wordpress
iptables -F f2b-plesk-wordpress
iptables -X f2b-plesk-wordpress -- stdout: ''
fail2ban.action         [13400]: ERROR   iptables -D INPUT -p tcp -m multiport --dports http,https,7080,7081 -j f2b-plesk-wordpress
iptables -F f2b-plesk-wordpress
iptables -X f2b-plesk-wordpress -- stderr: 'iptables: Too many links.\n'

Another symptom to look for is empty Iptables rules even though the Fail2Ban service is running on the server:

# iptables -nL
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination

Interestingly, the iptables update to the accurate one when we restart Fail2Ban. The errors are also no longer seen in the /var/log/fail2ban.log file.

How to resolve Fail2ban extension hangs in Plesk

According to our experienced Support Team, the Fail2ban extension hangs error is due to the Plesk bug: #PPPM-5090. Until it is fixed in one of the future updates, we can use the following workaround courtesy of our enterprising Support Engineers:

1. First, we will log in to Plesk.
2. Then, we have to navigate to Tools & Settings > Services Management > IP Address Banning (Fail2ban) in order to disable Fail2Ban.
3. Next, we head to Tools & Settings > Firewall > Enable Firewall Rules Management to enable Plesk Firewall.
4. After that, we will log in to the Plesk server via SSH.
5. Then, we have to save the iptables configuration with the following command:

   # iptables-save > /root/iptables-settings.conf
6. Next, we will disable Plesk Firewall by navigating to Tools & Settings > Firewall > Enable Firewall Rules Management. Furthermore, we have to restore the iptables rules via the following file:

   # iptables-restore < /root/iptables-settings.conf
7. Then we have to enable Fail2Ban by heading to Tools & Settings > Services Management > IP Address Banning (Fail2ban).
8. Finally, we will modify the /etc/rc.d/rc.local script in order to apply the iptables rules at boot time:

   # echo "iptables-restore < /root/iptables-restore.conf" >> /etc/rc.d/rc.local

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Conclusion

In brief, our skilled Support Engineers at Bobcares demonstrated how to deal with Fail2ban error in Plesk.