OpenVPN is an open source SSL VPN, which works in many Linux distributions.
Your VPN server will be accessable from several operating systems and smartphones.
There 2 ways to get to an openVPN server, but here i will show you the easier way.
For this tutorial: root access to your server is needed!
Download the latest software version for you distribution:
https://openvpn.net/index.php/access-server/download-openvpn-as-sw.html
On Ubuntu and Debian-like distributions:
wget https://THE_RIGHT_VERSION_OF_THE_PACKAGE_TO_YOUR_DISTRIBUTION.deb
In distributions which use the rpm package manager:
curl -O https://THE_RIGHT_VERSION_OF_THE_PACKEGE_TO_YOUR_DISTRIBUTION.rpm
sudo rpm -i openvpn-as....
Attention: Please you the appropriate bit version to your operating systems
Before you can log into the web interface of your VPN server,
you must set a password for the user openvpn:
sudo passwd openvpn
With the user openvpn and your selected password you can now log into the web interface of your vpn server:
https://your_ip_address_or_your_domainname_or_hostname:943/admin
Additional settings can be set now on that interface.
Clients can download the needed software and connecting profiles from this site:
https://your_ip_adress_or_your_domainname_or_hostname:943/
That is also the client login page from openVPN.
I recommed for further user to bind the access of the admin webinterface only on localhost.
(This can be set on the web interface)
The more complicated option and the second option would be to install openVPN from source.
Further information about that option:
https://openvpn.net/index.php/open-source/documentation/howto.html