This guide is intended to serve as documentation and is practically a copy and paste of the guide found on DigiCert website.
Source: https://www.digicert.com/ssl-certificate-installation-ubuntu-server-with-apache2.htm

With that said this guide is a great one for generating a self signed certificate on an Ubuntu server running Apache.

Let’s Begin!

What the Red Means

The lines that the user needs to enter or customize will be in red in this tutorial! The rest should mostly be copy-and-pastable.

About SSL Certificates

A SSL certificate is a way to encrypt a site’s information and create a more secure connection. Additionally, the certificate can show the virtual private server’s identification information to site visitors. Certificate Authorities can issue SSL certificates that verify the server’s details while a self-signed certificate has no 3rd party corroboration.

Set Up

The steps in this tutorial require the user to have root privileges on the VPS. You can see how to set that up here (DigiCert site) in steps 3 and 4.

Additionally, you need to have apache already installed and running on your virtual server. If this is not the case, you can download it with this command:

sudo apt-get install apache2

Step One—Activate the SSL Module

The next step is to enable SSL on the droplet.

sudo a2enmod ssl

Follow up by restarting Apache.

sudo service apache2 restart

Step Two—Create a New Directory

We need to create a new directory where we will store the server key and certificate

sudo mkdir /etc/apache2/ssl
sudo mkdir /etc/apache2/ssl/private
sudo chmod 755 /etc/apache2/ssl
sudo chmod 710 /etc/apache2/ssl/private

Note:
chmod 710 supports ssl-cert group under Ubuntu.
Setting permission to 700 on /etc/apache2/ssl/private will also work fine.

Set Ownership

sudo chown -R root:root /etc/apache2/ssl/
sudo chown -R root:ssl-cert /etc/apache2/ssl/private/

Note:
If you do not have ssl-cert group, just use ‘root:root’ on line above or skip 2nd line.

Place SSL files:

Put public www ssl certificate(s) along with intermediate certificate(s) in /etc/apache2/ssl
Put private ssl key(s) in /etc/apache2/ssl/private

Step Three—Create a Self Signed SSL Certificate

When we request a new certificate, we can specify how long the certificate should remain valid by changing the 365 to the number of days we prefer. As it stands this certificate will expire after one year.

sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/apache2/ssl/apache.key -out /etc/apache2/ssl/apache.crt

With this command, we will be both creating the self-signed SSL certificate and the server key that protects it, and placing both of them into the new directory.

This command will prompt terminal to display a lists of fields that need to be filled in.

The most important line is “Common Name”. Enter your official domain name here or, if you don’t have one yet, your site’s IP address.

You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:New York
Locality Name (eg, city) []:NYC
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Awesome Inc
Organizational Unit Name (eg, section) []:Dept of Merriment
Common Name (e.g. server FQDN or YOUR name) []:example.com                  
Email Address []:webmaster@awesomeinc.com

 

Step Four—Set Up the Certificate

Now we have all of the required components of the finished certificate.The next thing to do is to set up the virtual hosts to display the new certificate. Open up the SSL config file:

nano /etc/apache2/sites-available/default-ssl

Within the section that begins with <VirtualHost _default_:443>, quickly make the following changes. Add a line with your server name right below the Server Admin email:

ServerName example.com:443

Replace example.com with your DNS approved domain name or server IP address (it should be the same as the common name on the certificate). Find the following three lines, and make sure that they match the extensions below:

SSLEngine on
SSLCertificateFile /etc/apache2/ssl/apache.crt
SSLCertificateKeyFile /etc/apache2/ssl/private/apache.key

Note:
If you have a ChainBundle.crt file, include the additional line of:

SSLCertificateChainFile /etc/apache2/chain-bundle-file.crt

 

Save and Exit out of the file.

Step Five—Activate the New Virtual Host

Before the website that will come on the 443 port can be activated, we need to enable that Virtual Host:

sudo a2ensite default-ssl

You are all set. Restarting your Apache server will reload it with all of your changes in place.

sudo service apache2 reload

In your browser, type https://youraddress, and you will be able to see the new certificate.