CentOs yum configuration
These days I install a CentOs but I can't input in Chinese .This make me upset.Then I know it's the problem of yum.Then I changed the yum source.
第1步
wget http://mirrors.ustc.edu.cn/centos/CentOS-Base.5.mirrors.repo -O /etc/yum.repos.d/CentOS-Base.repo
备份yum配置文件，修改yum配置文件。
cp /etc/yum.repos.d/CentOS-Base.repo CentOS-Base.repo_bak
vi /etc/yum.repo.d/CentOS-Base.repo
可以用中科大(ustc)yum源，也可以用上海交大(sjtu)yum源，两者只能选一个。
用下面的内容覆盖CentOS-Base.repo就行了。
#中科大(ustc)yum源，http://centos.ustc.edu.cn/centos/5/就是最新的，
#也可以设置成http://centos.ustc.edu.cn/centos/5.5/
[base]
name=CentOS-5 - Base
baseurl=http://centos.ustc.edu.cn/centos/5/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#released updates
[update]
name=CentOS-5 - Updates
baseurl=http://centos.ustc.edu.cn/centos/5/updates/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#packages used/produced in the build but not released
[addons]
name=CentOS-5 - Addons
baseurl=http://centos.ustc.edu.cn/centos/5/addons/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-5 - Extras
baseurl=http://centos.ustc.edu.cn/centos/5/extras/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-5 - Plus
baseurl=http://centos.ustc.edu.cn/centos/5/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#contrib - packages by Centos Users
[contrib]
name=CentOS-5 - Contrib
baseurl=http://centos.ustc.edu.cn/centos/5/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#第一部分结束
#============分割线============注意，上下两部分只选一个
#sjtu yum源，http://ftp.sjtu.edu.cn/centos/5/就是最新的，
#也可以设置成http://ftp.sjtu.edu.cn/centos/5.5/
[base]
name=CentOS-5 - Base
baseurl=http://ftp.sjtu.edu.cn/centos/5/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#released updates
[update]
name=CentOS-5 - Updates
baseurl=http://ftp.sjtu.edu.cn/centos/5/updates/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#packages used/produced in the build but not released
[addons]
name=CentOS-5 - Addons
baseurl=http://ftp.sjtu.edu.cn/centos/5/addons/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#additional packages that may be useful
[extras]
name=CentOS-5 - Extras
baseurl=http://ftp.sjtu.edu.cn/centos/5/extras/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-5 - Plus
baseurl=http://ftp.sjtu.edu.cn/centos/5/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#contrib - packages by Centos Users
[contrib]
name=CentOS-5 - Contrib
baseurl=http://ftp.sjtu.edu.cn/centos/5/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos5
#第二部分结束
第2步
中科大(ustc)yum源
32位: rpm --import http://centos.ustc.edu.cn/centos/5/os/i386/RPM-GPG-KEY-CentOS-5
64位: rpm --import http://centos.ustc.edu.cn/centos/5/os/x86_64/RPM-GPG-KEY-CentOS-5
上海交大(sjtu)yum源
32位: rpm --import http://ftp.sjtu.edu.cn/centos/5/os/i386/RPM-GPG-KEY-CentOS-5
64位: rpm --import http://ftp.sjtu.edu.cn/centos/5/os/x86_64/RPM-GPG-KEY-CentOS-5
第3步
yum update
After that if you have a proble like that.Do like this:
每次yum install 时总是出现如下错误
http://mirrors.ustc.edu.cn/centos/6.0/extras/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 6 - "" |
Trying other mirror. |
Error: Cannot retrieve repository metadata (repomd.xml) for repository: extras. Please verify its path and try again |
此时聪明的我马上想到了是不是服务器解析不了域名了，导致repomd.xml下载不下来呢？
然后我就ping了一下mirrors.ustc.edu.cn ， 果然出现错误：ping: unknown host mirrors.ustc.edu.cn。显然是DNS配置问题了，DNS域名服务器IP地址配的不对。
把/etc/hosts里面 加了一行
mirrors.ustc.edu.cn 202.38.95.110 |
这样就可以解析mirrors.ustc.edu.cn了。yum成功！
小记：但是这不是解决这种问题最终办法。需要配置正确的DNS。方法是：打开/etc/resolv.conf 文件，加入一行 nameserver ip。此处把ip换成IDC运营商给的DNS的地址就可以了。
