红帽7.5更换yum源为centos源 操作步骤：参考以下链接。 标题：RedHat Enterprise Linux 6.4使用yum安装出现This system is not registered to Red Hat Subscription Management_天行健，君子以自强不息-CSDN博客 https://blog.csdn.net/ytx2014214081/article/details/78468947?utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7Edefault-14.control&dist_request_id=&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7EBlogCommendFromBaidu%7Edefault-14.control