It has come to our attention that users turning on the debug log feature found in the "Configure" menu under "Settings" are having trouble finding where the log is saved. This is because of a newer feature called PrivateTmp. This will create a tmp folder for each individual process that tries to write to temp. This means in our case you are looking for the tmp folder belonging to php-fpm.service. An example of what you would most likely see in this case in your tmp folder is provided below.
This has no negative effects on the system and in fact is a more secure method of using the tmp directory. If you are ok with this you can leave everything as is and simply open the php-fpm directory to find your in use tmp directory containing the debug_log.
If you wish to turn this feature of you may with a few short steps I will outline below.\
1) cp /lib/systemd/system/php-fpm.service /etc/systemd/system/
2) vi /etc/systemd/system/php-fpm.service
3) Edit "PrivateTmp=true" to "PrivateTmp=false" then write and quit (:wq)
4) systemctl restart php-fpm.service
In my personal testing I also needed to reboot the server but this may not be necessary in your case. If you have any questions, comments, or concerns with this FAQ please reach us at email@example.com.