cert.cnf

# openssl req -new -nodes -newkey rsa:2048 -keyout server-key.pem -out server-csr.pem -config cert.cnf
# openssl x509 -req -days 365 -in server-csr.pem -signkey server-key.pem -out server-cert.pem -extensions v3_req -extfile cert.cnf
# openssl x509 -in server-cert.pem -text -noout

[req]
default_bits = 2048
prompt = no
default_md = sha256
distinguished_name = dn
req_extensions = v3_req

[dn]
C = Country 
ST = State
L = Locality 
O = Company
OU = Unit
CN = site.common.name.com

[v3_req]
basicConstraints = CA:FALSE
keyUsage = nonRepudiation, digitalSignature, keyEncipherment
subjectAltName = @alt_names

[alt_names]
DNS.2 = site.alt.name.biz
DNS.3 = site.alt.name.io
DNS.4 = site.alt.name.net