redhat替换centos 6.6 yum源

新安装了redhat6.4.安装后，登录系统，使用yum update 更新系统。提示：

This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.

无法更新。

redhat 默认自带的 yum 源需要注册，才能更新。我们想不花钱也可以更新，需要替换掉redhat的yum源。

1.检查是否安装yum包

查看RHEL是否安装了yum，若是安装了，那么又有哪些yum包：

[root@localhost ~]# rpm -qa |grep yum

yum-metadata-parser-1.0-8.fc6

yum-3.0.1-5.el5

yum-rhn-plugin-0.4.3-1.el5

yum-updatesd-3.0.1-5.el5

2 删除redhat自带的yum包

卸载上面显示的所有yum包：

[root@localhost ~]# rpm -qa|grep yum|xargs rpm -e --nodeps（不检查依赖，直接删除rpm包）

再用

[root@localhost ~]# rpm -qa |grep yum

[root@localhost ~]# 

查看，无信息显示表示已经卸载完成。

3.下载新的yum包。使用Centos6.6的yum包

# wget http://mirrors.163.com/centos/6.5/os/i386/Packages/yum-metadata-parser-1.1.2-16.el6.i686.rpm


# wget http://mirrors.163.com/centos/6.5/os/i386/Packages/yum-3.2.29-40.el6.centos.noarch.rpm

# wget http://mirrors.163.com/centos/6.5/os/i386/Packages/yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm


安装yum软件包

注意:单个的安装包可能会依赖其它包（例如yum和yum-fastestmirror会相互依赖），所以我们可以把所有这些包放在一起，用一行命令将它们同时安装即可：

# rpm -ivh yum-metadata-parser-1.1.2-16.el6.i686.rpm yum-3.2.29-40.el6.centos.noarch.rpm yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm

4.更换yum源。使用163的源

# cd /etc/yum.repos.d/
# wget  http://mirrors.163.com/.help/CentOS6-Base-163.repo
# vi CentOS6-Base-163.repo

编辑文件，把文件里面的$releasever全部替换为版本号，即6.6 最后保存！或者直接把下面的内存拷贝到CentOS6-Base-163.repo文件中即可（已经修改好）

[base]
name=CentOS-6.6 - Base - 163.com
baseurl=http://mirrors.163.com/centos/6.6/os/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6.6&arch=$basearch&repo=os
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6


#released updates
[updates]
name=CentOS-6.6 - Updates - 163.com
baseurl=http://mirrors.163.com/centos/6.6/updates/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6.6&arch=$basearch&repo=updates
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6


#additional packages that may be useful
[extras]
name=CentOS-6.6 - Extras - 163.com
baseurl=http://mirrors.163.com/centos/6.6/extras/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6.6&arch=$basearch&repo=extras
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6


#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-6.6 - Plus - 163.com
baseurl=http://mirrors.163.com/centos/6.6/centosplus/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6.6&arch=$basearch&repo=centosplus
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6


#contrib - packages by Centos Users
[contrib]
name=CentOS-6.6 - Contrib - 163.com
baseurl=http://mirrors.163.com/centos/6.6/contrib/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6.6&arch=$basearch&repo=contrib
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

5.清除原有缓存

1	# yum clean all

重建缓存，以提高搜索安装软件的速度

1	# yum makecache

6.更新系统

1	# yum update

报错内容如下：

Loaded plugins: fastestmirror
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=6&arch=x86_64&repo=os error was
14: PYCURL ERROR 6 - "Couldn't resolve host 'mirrorlist.centos.org'"
Error: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please verify its path and try again

解决办法

1，执行

echo "nameserver 8.8.8.8" > /etc/resolv.conf

设置dns服务器

即可

找到问题的原因，是由于服务器没设置dns服务器地址导致的上述错误

1，执行

yum clean all

应该执行这两步即可。(第二步要不要执行有待验证)