卸载Redhat 7自带的yum，安装并使用网易163源

由于redhat的yum在线更新是收费的，如果没有注册的话不能使用，如果要使用，需将redhat的yum卸载后，安装CentOS yum工具，再配置其他源，以下为详细过程：
删除redhat原有的yum及RedHat订阅软件包

# rpm -qa | grep subscription-manager-* | xargs rpm -e
# rpm -e yum-3.4.3-132.el7.noarch --nodeps

安装163 yum软件包
# rpm -ivh http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-3.4.3-132.el7.centos.0.1.noarch.rpm
http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-34.el7.noarch.rpm

创建163 repo文件
# vim /etc/yum.repos.d/CentOS-Base-163.repo

[base]
name=CentOS-7 -Base
baseurl=http://mirrors.163.com/centos/7/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7

#released updates
[updates]
name=CentOS-7 - Updates
baseurl=http://mirrors.163.com/centos/7/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7

#additional packages that may be useful
[extras]
name=CentOS-7 - Extras
baseurl=http://mirrors.163.com/centos/7/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-7 - Plus
baseurl=http://mirrors.163.com/centos/7/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7

更新仓库缓存
#yum clean all
#yum makecache

列出所有仓库

# yum repolist

如果你运行yum update命令时，遇到以下错误，是因为你安装的是最小化系统，有些包缺失了
Delta RPMs disabled because /usr/bin/applydeltarpm not installed.

你需要安装deltarpm软件包，使用下面命令查看这个包的名称
yum provides '*/applydeltarpm'

然后安装它
# yum install deltarpm