Apache startup failed: Can’t locate API module structure `proxy.plesk_module’

Symptoms

• Apache service fails to start with the following errors:

  Can't locate API module structure `proxy.plesk_module' in file /usr/lib64/httpd/modules/mod_proxy.plesk.so: /usr/lib64/httpd/modules/mod_proxy.plesk.so: undefined symbol: proxy.plesk_module

  Cannot load /usr/lib64/httpd/modules/mod_proxy_fcgi.plesk.so into server: /usr/lib64/httpd/modules/mod_proxy_fcgi.plesk.so: undefined symbol: proxy_module

Cause

Corresponding modules are present in the Apache configuration file twice under different names:

mod_proxy_fcgi.so and mod_proxy_fcgi.plesk.so

mod_proxy.so and mod_proxy.plesk.so

Resolution

1. Connect to the server via SSH

2. Find the configuration file from where these modules are loaded:

   # egrep -R 'mod_proxy.plesk|mod_proxy_fcgi.plesk' /etc/httpd/
   /etc/httpd/conf.modules.d/00-base.conf: LoadModule proxy.plesk_module /usr/lib64/httpd/modules/mod_proxy.plesk.so
   /etc/httpd/conf.modules.d/00-base.conf: LoadModule proxy_fcgi.plesk_module /usr/lib64/httpd/modules/mod_proxy_fcgi.plesk.so

3. Edit /etc/httpd/conf.modules.d/00-base.conf and comment out above lines with a preceding "#":

   #LoadModule proxy.plesk_module /usr/lib64/httpd/modules/mod_proxy.plesk.so
   #LoadModule proxy_fcgi.plesk_module /usr/lib64/httpd/modules/mod_proxy_fcgi.plesk.so

4. Repair configuration files:

   # plesk repair web -y

5. Start apache if required:

   # service httpd start