After performing a default standalone install, the app configs are not able to be managed via the Tuning module. Logs show that it's due to the permissions of the file not allowing it from the www-data user:
[Mon Nov 12 03:23:23.677728 2018] [:error] [pid 30922] [client 71.233.0.82:41978] PHP Warning: file_put_contents(/opt/inquisition/conf/main.cfg): failed to open stream: Permission denied in /opt/inquisition/web/lib/Config.php on line 164
sysadmin@lhr1inquisition01:~/Inquisition$ ls -l /opt/inquisition/conf/main.cfg
-rw-r--r-- 1 inquisition inquisition 723 Nov 12 01:41 /opt/inquisition/conf/main.cfg
sysadmin@lhr1inquisition01:~/Inquisition$
After performing a default standalone install, the app configs are not able to be managed via the Tuning module. Logs show that it's due to the permissions of the file not allowing it from the www-data user: