RedHat yum源是收费的，没有注册的Redhat机器是不能使用yum源的。
1、当前系统环境：
系统版本：Red Hat Enterprise Linux Server release 7.3 (Maipo)
软件环境：系统默认是自带了yum程序的，需要卸载，安装CentOS的
2、更换yum源：
1) 卸载本地yum:
# rpm -qa|grep yum #查看本地yum
# rpm -qa|grep yum|xargs rpm -e --nodeps #卸载本地yum，不检查依赖性，卸载yum程序
# rpm -qa | grep Python-urlgrabber | xargs rpm -e --nodeps
2) 下载CentOS yum程序
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-3.4.3-161.el7.centos.noarch.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-50.el7.noarch.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
使用wget命令下载，也可以用浏览器下载。rpm包下载地址http://mirrors.163.com/centos/7/os/x86_64/Packages/ ，包的版本会有更新，选择最新版本下载
安装CentOS yum程序
为避免他们之间互相依赖，三个程序一起安装
# rpm -ivh yum-3.4.3-161.el7.centos.noarch.rpm yum-plugin-fastestmirror-1.1.31-50.el7.noarch.rpm yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
安装报错，依赖软件版本不兼容，
警告：yum-3.4.3-161.el7.centos.noarch.rpm: 头V3 RSA/SHA256 Signature, 密钥 ID f4a80eb5: NOKEY
错误：依赖检测失败：
python-urlgrabber >= 3.10-8 被 yum-3.4.3-161.el7.centos.noarch 需要
rpm >= 0:4.11.3-22 被 yum-3.4.3-161.el7.centos.noarch 需要
重新下载新版本的依赖软件，安装更新
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/rpm-4.11.3-35.el7.x86_64.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/rpm-libs-4.11.3-35.el7.x86_64.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/rpm-build-libs-4.11.3-35.el7.x86_64.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/rpm-python-4.11.3-35.el7.x86_64.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-chardet-2.2.1-1.el7_1.noarch.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-kitchen-1.1.1-5.el7.noarch.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/python-urlgrabber-3.10-9.el7.noarch.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/libxml2-python-2.9.1-6.el7_2.3.x86_64.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/rpm-4.11.3-35.el7.x86_64.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/rpm-sign-4.11.3-35.el7.x86_64.rpm
# wget http://mirrors.163.com/centos/7/os/x86_64/Packages/rpm-build-4.11.3-35.el7.x86_64.rpm
更新依赖软件：
# rpm –ivh python-*
# rpm -ivh libxml*
# rpm –Uvh rpm*
再次安装yum程序
# rpm -ivh yum-3.4.3-161.el7.centos.noarch.rpm yum-plugin-fastestmirror-1.1.31-50.el7.noarch.rpm yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
安装报错：
错误：依赖检测失败：
python-urlgrabber >= 3.10-8 被 yum-3.4.3-161.el7.centos.noarch 需要
Python-urlgrabber版本不兼容，下载对应的版本。
# wget ftp://ftp.icm.edu.pl/vol/rzm3/linux-centos-altarch/7.5.1804/os/armhfp/Packages/python-urlgrabber-3.10-8.el7.noarch.rpm
安装：
# rpm -ivh python-urlgrabber-3.10-8.el7.noarch.rpm
再次安装yum程序
# rpm -ivh yum-3.4.3-161.el7.centos.noarch.rpm yum-plugin-fastestmirror-1.1.31-50.el7.noarch.rpm yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
安装成功。
3) repo 配置文件
下载配置文件
# cd /etc/yum.repos.d/ #进入到yum配置文件目录
# wget http://mirrors.163.com/.help/CentOS7-Base-163.repo #下载配置文件
设置配置文件
# sed -i "s;\$releasever;7;g" CentOS7-Base-163.repo
替换新的repo文件
# mv redhat.repo redhat.repo.bak
配置文件内容如下：
[base]
name=CentOS-7 - Base - 163.com
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
baseurl=http://mirrors.163.com/centos/7/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7
#released updates
[updates]
name=CentOS-7 - Updates - 163.com
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
baseurl=http://mirrors.163.com/centos/7/updates/$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 - 163.com
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
baseurl=http://mirrors.163.com/centos/7/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-7 - Plus - 163.com
baseurl=http://mirrors.163.com/centos/7/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7
更新yum缓存
# yum clean all #清除yum缓存
# yum makecache #更新yum缓存
执行yumrepolist查看，如果显示出repo仓库列表，并显示软件包数量则OK。
# yum repolist
至此yum源更换完成。
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