修改Centos的yum源
yum安装方式在有网络环境的时候非常方便，选择一个比较快的yum源是非常有意义的
(1)自动选择最快的源
由于yum中有的mirror速度是非常慢的，如果yum选择了这个mirror，这个时候yum就会非常慢，对此，可以下载fastestmirror插件，它会自动选择最快的mirror：
yum install yum-fastestmirror -y
fastestmirror配置文件：（一般不用动）
/etc/yum/pluginconf.d/fastestmirror.conf
你的yum镜像的速度测试记录文件：
/var/cache/yum/timedhosts.txt
(2)一直受不了centos的更新源的速度，现在弄好了。更新200多MB的东东，5分钟搞定。
1 mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.old
2 创建新的repo文件
vi /etc/yum.repos.d/CentOS-Base.repo
引用
# CentOS-Base.repo
#
# This file uses a new mirrorlist system developed by Lance Davis for CentOS.
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-5.0 - Base
baseurl=http://mirror.be10.com/centos/5/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#released updates
[update]
name=CentOS-5.0 - Updates
baseurl=http://mirror.be10.com/centos/5/updates/$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-5.0 - Addons
baseurl=http://mirror.be10.com/centos/5/addons/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-5.0 - Extras
baseurl=http://mirror.be10.com/centos/5/extras/$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-5.0 - Plus
baseurl=http://mirror.be10.com/centos/5/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#contrib - packages by Centos Users
[contrib]
name=CentOS-5.0 - Contrib
baseurl=http://mirror.be10.com/centos/5/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
#packages in testing
[testing]
name=CentOS-5.0 - Testing
baseurl=http://mirror.be10.com/centos/5.0/testing/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
rpm --import http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5
[root@localhost yum.repos.d]# yum upgrade
