# Solved: Invalid command ‘SSLEngine

## Problem

Apache refuses to start prompting *Invalid command 'SSLEngine'Error'*

### Cause of the problem

This frequently happens on fresh Apache servers. When Apache starts it reads
through the configuration files. When it encounters `SSLEngine` directive, it
considers it as unknown. This is caused by the fact that the server’s basic
configuration does not have `mod_ssl` module installed or enabled.

## Solution

### On CentOS/RedHat systems

Run the following command to install `mod_ssl`

```bash
sudo yum install mod_ssl
```

### On Ubuntu/Debian systems

Run the following command to enable the module:

```bash
sudo a2enmod ssl
```

SSL module should be enabled by now.