Invalid command SSLEngine Error occurs when Apache web server fails after the virtual host is configured to use the SSL service on port 443.

As part of our Server Support Services, we have previously helped customers in solving Apache web server issues.

In this context, we shall look into the reason for this error and how to fix it.

More about invalid command SSLEngine Error in Apache web server

We will describe briefly why this error occurs.

i. When the SSL module mod_ssl in the configuration file of the web server detects that the directive "SSLEngine" is not valid.In this case the SSL service will fail and throw an SSLEngine Error.

ii. Errors in the configuration file "/etc/httpd/conf.d" can also result to this error.

How to solve invalid command SSLEngine Error in Apache web server

To fix SSLEngine Error in Apache, apply the following methods;

i. Get mod_ssl installed

You need to check if mod_ssl module is installed and if so it is important to enable it to enable the SSLEngine to function properly. In CentOS, log into the server via ssh as the root user and you can use the following command to install mod_ssl;

sudo yum install mod_ssl

For apache version 2.4, you can use;

sudo yum install mod24_ssl

Next you can enable mod_ssl module in Ubuntu/Debian  after installation with the command below;

sudo a2enmod ssl

As a norm in Linux, after making changes in the web server configuration file, you need to restart the service to effect changes. To do this use the command below;

sudo apachectl restart

To verify that it is working correctly, use the command below;

openssl s_client -connect website.com:443

ii. The SSL module should be Loaded.

What this means is that in some scenarios, the error could result from not loading the SSL module. Therefore, you can load the LoadModule of the SSL with the command below;

LoadModule ssl_module /usr/lib64/apache2-prefork/mod_ssl.so

iii. Remove any configuration which is not being used by Apache configuration file

Unused config directives in the configuration file could cause some serious issues and possible affect the functioning of the SSLEngine module. Therefore you can remove them from the configuration file located at  "/etc/httpd/conf" with the command below;

grep SSL /etc/httpd/{conf,conf.d} -r

All these approaches are very effective in solving SSLEngine Error in Apache.

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