Apache cannot be started on a Plesk server: Configuration error: No MPM loaded

Symptoms

• Plesk Obsidian running on a RHEL-based operating system
• Unable to start the Apache web server service (httpd) on CentOS 7
• Running the systemctl status httpd command reveals an error that is similar to the following:
  

  CONFIG_TEXT: AH00534: httpd: Configuration error: No MPM loaded

Cause

The Apache configuration files /etc/httpd/conf/httpd.conf and/or /etc/httpd/conf.modules.d/00-mpm.conf is empty, corrupted or misconfigured.

Resolution

Replace the contents of the file /etc/httpd/conf/httpd.conf and/or /etc/httpd/conf.modules.d/00-mpm.conf with the contents of the same file, but taken from a properly working Plesk server.

OR

Undo any recent manual changes that have been done to either of these files

OR

Replace the file /etc/httpd/conf/httpd.conf from the original package by doing the following:

1. Log into your server via SSH

2. Make sure all of the necessary utilities are installed:

# yum install yum-utils

3. Download the httpd package archive:

# yumdownloader httpd

4.Extract the contents of the package archive:

# rpm2cpio httpd-* | cpio -idmv

5. Replace the default httpd.conf file from the package with the current one:

# cp ./etc/httpd/conf/httpd.conf /etc/httpd/conf/httpd.conf

Keep in mind that there are some differences between Plesk httpd.conf and the default one depending on nginx and not only:

# diff etc/httpd/conf/httpd.conf /etc/httpd/conf/httpd.conf
42c42
< Listen 80
---
> Listen 7080
164c164
< DirectoryIndex index.html
---
> DirectoryIndex index.html index.shtml index.cfm index.php index.htm
196c196
< LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
---
> LogFormat "%a %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
198d197
<
201c200
< LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %I %O" combinedio
---
> LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %I %O" combinedio
316c315
< AddDefaultCharset UTF-8
---
> #AddDefaultCharset UTF-8
353a353,357
> GracefulShutDownTimeout 3
> AddOutputFilter INCLUDES .shtml
> AddType text/html .shtml
> AddType application/x-httpd-php .php
> AddType application/x-httpd-php-source .phps