下載rhel7.0 官網提供的SHA-256 驗證碼爲：
SHA-256: 85a9fedc2bf0fc825cc7817056aa00b3ea87d7e111e0cf8de77d3ba643f8646c
校驗方法爲：
hufu@hufu-ThinkPad-R400:/media/hufu/U$ sha256sum rhel-server-7.0-x86_64-dvd.iso
85a9fedc2bf0fc825cc7817056aa00b3ea87d7e111e0cf8de77d3ba643f8646c rhel-server-7.0-x86_64-dvd.iso
通過比對下載ISO文件驗證通過