如果你安装了CentOS系统，并且yum更新慢的话，可以考虑将更新源更换为 网易提供的源：mirrors.163.com
具体操作如下：
cd /etc/yum.repos.d/
mv CentOS-Base.repo CentOS-Base.repo.bak
vi CentOS-Base.repo
加入如下内容：
CentOS-Base.repo下载: CentOS-Base.repo# 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-$releasever - Base  
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os  
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/   
baseurl=http://mirrors.163.com/centos/$releasever/os/$basearch/   
gpgcheck=1   
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5  
 
#released updates      
[updates]   
name=CentOS-$releasever - Updates  
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates  
#baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/   
baseurl=http://mirrors.163.com/centos/$releasever/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-$releasever - Addons  
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=addons  
#baseurl=http://mirror.centos.org/centos/$releasever/addons/$basearch/   
baseurl=http://mirrors.163.com/centos/$releasever/addons/$basearch/   
gpgcheck=1   
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5  
 
#additional packages that may be useful   
[extras]   
name=CentOS-$releasever - Extras  
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras  
#baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/   
baseurl=http://mirrors.163.com/centos/$releasever/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-$releasever - Plus  
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus  
#baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/   
baseurl=http://mirrors.163.com/centos/$releasever/centosplus/$basearch/   
gpgcheck=1   
enabled=0   
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-5