EasyRSA is a CLI utility to build and manage a PKI CA. Initially part of the
OpenVPN project (www.openvpn.net), now maintained by the community.

The EasyRSA package and scripts are installed under /usr/share/easyrsa. They
can be copied anywhere else convenient when they are to be used.

Further instructions for version 3 usage at:
https://community.openvpn.net/openvpn/wiki/EasyRSA3-OpenVPN-Howto