$ sudo openssl genrsa -out foo.example.com.key 2048
$ sudo openssl req -new -key foo.example.com.key -out foo.example.com.csr

$ sudo openssl x509 -req -days 730 -in foo.example.com.csr -signkey foo.example.com.key -out foo.example.com.crt
Signature ok
subject=/C=GB/ST=England/L=London/O=Example Co. Ltd./CN=foo.example.com
Getting Private key

$ openssl x509 -in foo.example.com.crt -noout -text