PHP-FPM handler failed to be configured for domain on Plesk for Linux server: An another FPM instance seems to already listen on

Symptoms

• PHP-FPM handler failed to be configured for the domain. When pressing OK in Plesk in Domains > example.com > PHP Settings, the following error appears:

  phpinimng failed: invoke-rc.d:initscript plesk-php72-fpm, action "status" failed. invoke-rc.d:initscript plesk-php72-fpm, action "status" failed.Service plesk-php72-fpm is down after attempt to start it.

• The same error appears when trying to start the corresponding PHP-FPM service in Tools & Settings > Services Management

• The log file /var/log/plesk-php72-fpm/error.log contains the following error:

  NOTICE: configuration file /opt/plesk/php/7.2/etc/php-fpm.conf test is successful
  ERROR: An another FPM instance seems to already listen on /var/www/vhosts/system/example.com/php-fpm.sock
  ERROR: FPM initialization failed

  Note: PHP version may differ from 7.2 (e.g., it can be 7.3)

Cause

Leftover Domain PHP configuration files causing a conflict with the current PHP version selected in Domains > example.com > PHP Settings

Resolution

1. Connect to the server via SSH

2. Download and unpack the script to find all conflicting configuration files:

   # curl -LO https://support.plesk.com/hc/en-us/article_attachments/12377594509335/115002165905-find-extra-config-files.php.tar.gz

   # tar xf 115002165905-find-extra-config-files.php.tar.gz

3. Run the script to get a list of the configuration files:

   # plesk php 115002165905-find-extra-config-files.php
   [CRIT] File /etc/php/7.0/fpm/pool.d/example.com.conf may cause PHP failure: domain example.com has "plesk-php72-fpm" handler specified, but this file is used to configure "fpm" handler!
   [CRIT] File /etc/php/7.0/fpm/pool.d/example.org.conf may cause PHP failure: domain example.org has "plesk-php72-fpm" handler specified, but this file is used to configure "fpm" handler!

4. Remove all the configuration files mentioned above:

   # rm /etc/php/7.0/fpm/pool.d/example.com.conf /etc/php/7.0/fpm/pool.d/example.org.conf

5. Restart the PHP-FPM services:

   # systemctl restart plesk-php* php*

6. Recreate the PHP-FPM sockets and configuration files:

   # plesk bin php_settings -u