【無償SSL】Let's Encrypt 使ってみる。 ref: http://qiita.com/yasuken/items/e45eb9efd16199512d4e

file0.txt

$ sudo su

// Apache インストール
# yum install httpd

// Apache 起動、自動起動オン
# systemctl start httpd.service
# systemctl enable httpd.service

// HTTP/HTTPS ウェルウンポート開放
# firewall-cmd --permanent --zone=public --add-service=http 
# firewall-cmd --permanent --zone=public --add-service=https
# firewall-cmd --reload

// SSLモジュール、OpenSSL インストール
# yum install mod_ssl openssl

// epel インストール
# yum install epel-release

// epel からcertbot、certbot-apache インストール
# yum --enablerepo=epel install certbot python-certbot-apache

// certonly コマンドで、SSL/TLS サーバ証明書を取得する
# certbot certonly
Saving debug log to /var/log/letsencrypt/letsencrypt.log

How would you like to authenticate with the ACME CA?
-------------------------------------------------------------------------------
1: Apache Web Server plugin - Beta (apache)
2: Place files in webroot directory (webroot)
3: Spin up a temporary webserver (standalone)
-------------------------------------------------------------------------------

// Apache 使用するので1
Select the appropriate number [1-3] then [enter] (press 'c' to cancel): 1
Starting new HTTPS connection (1): acme-v01.api.letsencrypt.org

// Domain を指定
Please enter in your domain name(s) (comma and/or space separated)  (Enter 'c'
to cancel):ssl-test.yasuken1990.com
Obtaining a new certificate
Performing the following challenges:
tls-sni-01 challenge for ssl-test.yasuken1990.com

We were unable to find a vhost with a ServerName or Address of ssl-test.yasuken1990.com.
Which virtual host would you like to choose?
(note: conf files with multiple vhosts are not yet supported)
-------------------------------------------------------------------------------
1: ssl.conf                       |                       | HTTPS | Enabled
-------------------------------------------------------------------------------

// 1を選ぶしかない件なので
Press 1 [enter] to confirm the selection (press 'c' to cancel): 1
Waiting for verification...
Cleaning up challenges
Generating key (2048 bits): /etc/letsencrypt/keys/0000_key-certbot.pem
Creating CSR: /etc/letsencrypt/csr/0000_csr-certbot.pem

IMPORTANT NOTES:
 - Congratulations! Your certificate and chain have been saved at

// /etc/letsencrypt/live/ssl-test.yasuken1990.com/ に色々作られた
   /etc/letsencrypt/live/ssl-test.yasuken1990.com/fullchain.pem. Your
   cert will expire on 2017-06-12. To obtain a new or tweaked version
   of this certificate in the future, simply run certbot again. To
   non-interactively renew *all* of your certificates, run "certbot
   renew"
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:   https://letsencrypt.org/donate
   Donating to

file1.vim

#DocumentRoot "/var/www/html"
#ServerName www.example.com:443

// コメントになっているので、コピーして自分の環境にあった設定をする
DocumentRoot "/var/www/html"
ServerName ssl-test.yasuken1990.com:443

file2.txt

// Apache再起動
# systemctl restart httpd.service