為example.com域名生成一個自簽的證書
$ mkdir certs; cd certs;
$ openssl req -nodes -new -x509 \
-keyout example-com.key -out example-com.crt \
-days 365 \
-subj '/CN=example.com/O=youdianzhishi./C=CN';
Generating a RSA private key
..+++++
.................................................................................................................+++++
writing new private key to 'example-com.key'
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$ cd -