Let's Encrypt Certbot SSL

certbot (webroot)

certbot certonly --webroot -w /path/to/public_html \
  --email admin@example.com --agree-tos --rsa-key-size 4096 \
  -d example.com

certbot-auto (레거시 CentOS 6)

./certbot-auto certonly --webroot -w /path/to/public_html \
  --server https://acme-v02.api.letsencrypt.org/directory \
  --email admin@example.com --agree-tos -d example.com

ACME v01 deprecated. v02 권장.