因为redhat中的yum是收费的，未注册时不允许使用的，下面是挂载光盘后的情况，未挂载是没有yum命令。但是下面即便挂载了也是需要验证的
[root@localhost /]# yum install openssl Loaded plugins: product-id, refresh-packagekit, security, subscription-manager Updating certificate-based repositories. Unable to read consumer identity Setting up Install Process Nothing to do
所以最好是去使用centos的yum源，免费的。
推文：https://blog.csdn.net/yingfengjia520/article/details/54866007
安装步骤：
一：查看原来的yum源，删除原有yum源
rpm -aq | grep yum #查看
rpm -aq | grep yum|xargs rpm -e --nodeps #删除
二：下载centos的yum安装包
这里使用网易的yum源即可，快些
http://mirrors.163.com/centos/6/os/x86_64/Packages/ #修改前面的6可以修改centos版本 注意（x86_64是64位系统，i386是32位）
安装yum源的相关依赖包
http://mirrors.163.com/centos/6/os/x86_64/Packages/python-urlgrabber-3.9.1-11.el6.noarch.rpm
http://mirrors.163.com/centos/6/os/x86_64/Packages/python-iniparse-0.3.1-2.1.el6.noarch.rpm
yum源包
http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-3.2.29-81.el6.centos.noarch.rpm
http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-metadata-parser-1.1.2-16.el6.x86_64.rpm
http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.30-40.el6.noarch.rpm
http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-updateonboot-1.1.30-40.el6.noarch.rpm
http://mirrors.163.com/centos/6/os/x86_64/Packages/yum-utils-1.1.30-40.el6.noarch.rpm
注意：在上面yum源包中yum=metadata-parser是需要系统版本要求，需要64位，这里我们的系统是32位，会出现错误
error: Failed dependencies: libc.so.6()(64bit) is needed by yum-metadata-parser-1.1.2-16.el6.x86_64 libc.so.6(GLIBC_2.2.5)(64bit) is needed by yum-metadata-parser-1.1.2-16.el6.x86_64 libglib-2.0.so.0()(64bit) is needed by yum-metadata-parser-1.1.2-16.el6.x86_64 libpthread.so.0()(64bit) is needed by yum-metadata-parser-1.1.2-16.el6.x86_64 libpython2.6.so.1.0()(64bit) is needed by yum-metadata-parser-1.1.2-16.el6.x86_64 libsqlite3.so.0()(64bit) is needed by yum-metadata-parser-1.1.2-16.el6.x86_64 libxml2.so.2()(64bit) is needed by yum-metadata-parser-1.1.2-16.el6.x86_64 libxml2.so.2(LIBXML2_2.4.30)(64bit) is needed by yum-metadata-parser-1.1.2-16.el6.x86_64