Create CA key

openssl genrsa -aes256 -out ca.key 4096

Generate a CA certificate

openssl req -new -x509 -sha256 -days 3650 -key ca.key -out ca.crt

Create a private key for a certificate

openssl genrsa -out siteprivate.key 4096

Create a CSR

openssl req -new -sha256 -subj "/CN=www.example.com" -key siteprivate.key -out site.csr

Create a EXT config

echo "subjectAltName=DNS:*.example.com,IP:192.168.1.100" > ext.cnf

Generate a site certificate

openssl x509 -req -sha256 -days 3650 -CA ca.crt -CAkey ca.key -in site.csr -out site.crt -extfile ext.cnf -CAcreateserial