In Debian, install openvpn with easy-rsa. Then:
# cd /etc/openvpn/easy-rsa # source ./vars # ./build-dh
-----BEGIN DH PARAMETERS----- MIIBCAKCAQEA3Mdx5SV5kjdmq+QdTG+JIwkqdlsrXYitOTUK2GQdlRI9JhYFW3cZ 6R1oLy14JbhTKTHEzRrljePCyJJDq1gAVAcIdIazNWFRnuAMRN5HdJcDyXluaajO k3u9HDVlIyTIDiJC6fNXuq76AQV1J+8V5t2s+nqhYFIjxxeXdSdGqeGlINgM+kMm cRZa77UTk3MZK0uEjxeZNFnMIW+laCUT96YB8Vs+PH+7JPeMPBWJP7yQmrSEkOgD h8BxnE+P+6lTgtNgd1wKDzdGd8wES7ObXhAcxhZnKSUIUyuzzaJtXDMsj/rXXQip xIXKARi8X7uCaYZUEh5qC2F+uBoPjV6NywIBAg== -----END DH PARAMETERS-----
openssl dhparam -out dhparam.pem 2048
In Debian, install openvpn with easy-rsa. Then:
Some time (depending on sources of randomness) later, you'll have a unique dh2048.pem key, aka prime, such as this one I just created: