第一步，备份老的yum源
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.old
第二步，下载阿里云的yum源
cd /etc/yum.repos.d/
wget -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
[root@localhost yum.repos.d]# ls -lrt
total 24
-rw-r--r--. 1 root root 3664 Nov 27 2013 CentOS-Vault.repo
-rw-r--r--. 1 root root 630 Nov 27 2013 CentOS-Media.repo
-rw-r--r--. 1 root root 638 Nov 27 2013 CentOS-Debuginfo.repo
-rw-r--r--. 1 root root 1926 Nov 27 2013 CentOS-Base.repo.old
-rw-r--r--. 1 root root 2572 May 14 2015 Centos-6.repo
-rw-r--r--. 1 root root 460 Jul 23 23:28 CentOS-Base.repo
说明：
centos5可以用下面的源：
wget -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo
第三步，更新源
[root@localhost yum.repos.d]# mv Centos-6.repo CentOS-Base.repo
mv: overwrite `CentOS-Base.repo'? y
第四步，清理下载的header和packages
yum clean headers清除header，yum clean packages清除下载的rpm包，yum clean all一全部清除。
[root@localhost yum.repos.d]# yum clean all
Loaded plugins: fastestmirror,refresh-packagekit,security
Cleaning repos: base extras updates
Cleaning up Everything
Cleaning up list of fastest mirrors
第五步，生成header和package缓存
yum makecache 是 将服务器上的软件包信息现在本地缓存,以提高搜索安装软件的速度
[root@localhost yum.repos.d]# yum makecache
Loaded plugins: fastestmirror,security
Determining fastest mirrors
* base: mirrors.aliyun.com
* extras: mirrors.aliyun.com
* updates: mirrors.aliyun.com
base | 3.7 kB 00:00
base/group_gz | 226 kB 00:00
base/filelists_db | 6.4 MB 00:06
base/primary_db | 4.7 MB 00:04
base/other_db | 2.8 MB 00:02
extras | 3.4 kB 00:00
extras/filelists_db | 25 kB 00:00
extras/prestodelta | 1.3 kB 00:00
extras/primary_db | 29 kB 00:00
extras/other_db | 30 kB 00:00
updates | 3.4 kB 00:00
updates/filelists_db | 1.6 MB 00:01
updates/prestodelta | 66 kB 00:00
updates/primary_db | 2.5 MB 00:02
updates/other_db | 34 MB 00:33
Metadata Cache Created
[root@localhost yum.repos.d]#
第六步，安装一个软件试验一下
[root@localhost yum.repos.d]# yum install vsftpd
Loaded plugins: fastestmirror,security
Loading mirror speeds from cached hostfile
* base: mirrors.aliyun.com
* extras: mirrors.aliyun.com
* updates: mirrors.aliyun.com
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package vsftpd.x86_64 0:2.2.2-24.el6 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
=============================================================================================================================================================================================================================================
Package Arch Version Repository Size
=============================================================================================================================================================================================================================================
Installing:
vsftpd x86_64 2.2.2-24.el6 base 156 k
Transaction Summary
=============================================================================================================================================================================================================================================
Install 1 Package(s)
Total download size: 156 k
Installed size: 340 k
Is this ok [y/N]: y
Downloading Packages:
http://mirrors.aliyun.com/centos/6/os/x86_64/Packages/vsftpd-2.2.2-24.el6.x86_64.rpm: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'mirrors.aliyun.com'"
Trying other mirror.
http://mirrors.aliyuncs.com/centos/6/os/x86_64/Packages/vsftpd-2.2.2-24.el6.x86_64.rpm: [Errno 14] PYCURL ERROR 6 - "Couldn't resolve host 'mirrors.aliyuncs.com'"
Trying other mirror.
Error Downloading Packages:
vsftpd-2.2.2-24.el6.x86_64: failure: Packages/vsftpd-2.2.2-24.el6.x86_64.rpm from base: [Errno 256] No more mirrors to try.
我们发现报错Couldn’t resolve host ‘mirrors.aliyun.com，需要更新一下DNS。
第七步，更新DNS
[root@localhost yum.repos.d]# vi /etc/resolv.conf
增加一行
nameserver 8.8.8.8
再次试验
[root@localhost yum.repos.d]# yum install vsftpd
Loaded plugins: fastestmirror,security
Loading mirror speeds from cached hostfile
* base: mirrors.aliyun.com
* extras: mirrors.aliyun.com
* updates: mirrors.aliyun.com
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package vsftpd.x86_64 0:2.2.2-24.el6 will be installed
--> Finished Dependency Resolution
Dependencies Resolved
=============================================================================================================================================================================================================================================
Package Arch Version Repository Size
=============================================================================================================================================================================================================================================
Installing:
vsftpd x86_64 2.2.2-24.el6 base 156 k
Transaction Summary
=============================================================================================================================================================================================================================================
Install 1 Package(s)
Total download size: 156 k
Installed size: 340 k
Is this ok [y/N]: y
Downloading Packages:
vsftpd-2.2.2-24.el6.x86_64.rpm | 156 kB 00:00
warning: rpmts_HdrFromFdno: Header V3 RSA/SHA1 Signature,key ID c105b9de: NOKEY
Retrieving key from http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-6
Importing GPG key 0xC105B9DE:
Userid: "CentOS-6 Key (CentOS 6 Official Signing Key) <centos-6-key@centos.org>"
From : http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-6
Is this ok [y/N]: y
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Installing : vsftpd-2.2.2-24.el6.x86_64 1/1
Verifying : vsftpd-2.2.2-24.el6.x86_64 1/1
Installed:
vsftpd.x86_64 0:2.2.2-24.el6
Complete!
[root@localhost yum.repos.d]#
补充
yum 主要的一下命令如下:
yum search 软件包 搜索软件包
yum install 软件包 安装软件包
yum remove 软件包
yum update 更新系统
我们也可以更新软件包源为163或者中科大的：
http://mirrors.163.com/ 163镜像地址
http://centos.ustc.edu.cn/ 中科大镜像地址
可以通过更改baseurl的方式进行更新，具体搜索网上资料即可，推荐下面一篇：
http://www.cnblogs.com/mchina/archive/2013/01/04/2842275.html
