CSF/LFD fails to start upon install

Symptoms

You install the third-party ConfigServer CSF/LFD firewall software, and it fails to start with errors like these:

[root@server]# /bin/systemctl status lfd.service
● lfd.service - ConfigServer Firewall & Security - lfd
   Loaded: loaded (/usr/lib/systemd/system/lfd.service; enabled; vendor preset: disabled)
   Active: failed (Result: signal) since Thu 2020-09-24 23:25:00 IDT; 5min ago
  Process: 9544 ExecStart=/usr/sbin/lfd (code=killed, signal=KILL)
 CSF/LFD
Sep 24 23:25:00 server systemd[1]: Starting ConfigServer Firewall & Security - lfd...
Sep 24 23:25:00 server systemd[1]: lfd.service: control process exited, code=killed status=9
Sep 24 23:25:00 server systemd[1]: Failed to start ConfigServer Firewall & Security - lfd.
Sep 24 23:25:00 server systemd[1]: Unit lfd.service entered failed state.
Sep 24 23:25:00 server systemd[1]: lfd.service failed.

Description 

When you first install CSF/LFD, it runs in TESTING mode and does not start. The LFD error log shows errors like these:

[root@server]# tail /var/log/lfd.log 
Sep 24 23:04:17 server lfd[8947]: *Error* lfd will not run with TESTING enabled in /etc/csf/csf.conf, at line 83
Sep 24 23:04:17 server lfd[8947]: daemon stopped
Sep 24 23:09:31 server lfd[9099]: *Error* lfd will not run with TESTING enabled in /etc/csf/csf.conf, at line 83
Sep 24 23:09:31 server lfd[9099]: daemon stopped
Sep 24 23:14:40 server lfd[9249]: *Error* lfd will not run with TESTING enabled in /etc/csf/csf.conf, at line 83
Sep 24 23:14:40 server lfd[9249]: daemon stopped
Sep 24 23:19:50 server lfd[9390]: *Error* lfd will not run with TESTING enabled in /etc/csf/csf.conf, at line 83
Sep 24 23:19:50 server lfd[9390]: daemon stopped
Sep 24 23:25:00 server lfd[9544]: *Error* lfd will not run with TESTING enabled in /etc/csf/csf.conf, at line 83
Sep 24 23:25:00 server lfd[9544]: daemon stopped

Workaround

Either set TESTING = "0" in the /etc/csf/csf.conf file and restart CSF/LFD, or disable TESTING mode in the Firewall Configuration in WHM at "Home / Plugins / ConfigServer Security & Firewall".

Please note, CSF/LFD is third-party software not provided by cPanel. For further assistance with CSF/LFD, contact ConfigServer, the vendor for CSF/LFD at the following link:

ConfigServer Community Forum: General Discussion (csf)