You may find that a website is producing "503 Service Unavailable" errors when you visit your browser and the Apache error log, /etc/apache2/logs/error_log, shows entries similar to the following.
[Wed Mar 31 03:19:07.111327 2021] [proxy_fcgi:error] [pid 17628] [client xxx.xxx.xxx.xxx:0] AH01079: failed to make connection to backend: httpd-UDS
When checking in WHM at "Home » Software » MultiPHP Manager," the domain that is having the problem shows that PHP FPM is disabled or unavailable for the domain.
If PHP FPM was disabled incorrectly, or a problem occurred on the server that left cruft PHP FPM configuration files in place when they should not be there, it could cause this problem to occur.
- Login to the server via SSH or "Terminal" as the 'root' user.
- Run the following command to verify that one or more cruft files exist.
- If that command shows a list of cruft files at the end, you must either delete or move the files to a different location on the server.
Please note, it is recommended to move the files out of the way so that you may examine or restore the files later if needed.
- Run the following command to rebuild the FPM configuration and restart Apache.
/usr/local/cpanel/scripts/php_fpm_config --rebuild --check
- Visit your domain to confirm that the 503 error has been resolved