Knowledge Base

Apache fails to start on a Plesk server after Apache update on CentOS 7 / RHEL 7

Apache package httpd was updated to 2.4.6-98.el7 on CentOS 7 / Red Hat Enterprise Linux 7:

# rpm -qa|grep httpd
httpd-2.4.6-98.el7_9.6.x86_64
Apache service fails to start. Configuration check (httpd -t command) reports one of the following error messages:

httpd: Syntax error on line 56 of /etc/httpd/conf/httpd.conf: Syntax error on line 7 of /etc/httpd/conf.modules.d/00-proxy.conf: Cannot load modules/mod_proxy_ajp.so into server: /etc/httpd/modules/mod_proxy_ajp.so: undefined symbol: ap_proxy_check_connection

httpd: Syntax error on line 56 of /etc/httpd/conf/httpd.conf: Syntax error on line 14 of /etc/httpd/conf.modules.d/00-proxy.conf: Cannot load modules/mod_proxy_http.so into server: /etc/httpd/modules/mod_proxy_http.so: undefined symbol: ap_proxy_check_connection

httpd: Syntax error on line 56 of /etc/httpd/conf/httpd.conf: Syntax error on line 7 of /etc/httpd/conf.modules.d/00-proxy.conf: Cannot load modules/mod_proxy_ajp.so into server: /etc/httpd/modules/mod_proxy_ajp.so: undefined symbol: proxy_module
The following error may appear on the Home page in Plesk:

Failed to update the ModSecurity rule set. Details

Product issue:

#PPP-59844 "Updated Apache mod_proxy to fix the issue where Apache did not start after an update of httpd to 2.4.6-98 on RHEL 7/CentOS 7/CloudLinux 7."
Fixed in:
- Plesk Obsidian 18.0.43-18.0.49 mod_proxy update 27 January 2023 (Linux)
- Plesk Onyx 17.5, 17.8 mod_proxy update 27 January 2023 (Linux)

Please consider updating your server:

Install latest Plesk updates.

Connect to the server via SSH.
Download the patched psa-mod_proxy.rpm package:

# wget https://support.plesk.com/hc/en-us/article_attachments/9861700053010/psa-mod_proxy.rpm
Install the downloaded package:

# rpm -Uvh psa-mod_proxy.rpm
Start the Apache service:

# service httpd start
Repair web server configuraiton files:

# plesk repair web -y
If applicable, update ModSecurity ruleset:

# plesk daily UpdateModSecurityRuleSet

If the update is not possible for some reason apply the following

Connect to the Plesk server via SSH.
Download the patched psa-mod_proxy.rpm package:

# wget https://support.plesk.com/hc/en-us/article_attachments/12376918710167/psa-mod_proxy.rpm
Install the downloaded package:

# rpm -Uvh psa-mod_proxy.rpm
Start the Apache service:

# service httpd start