1. 换源，教育网内东北大学，中国科技大学，上海交通大学，西安交通大学等高校都有相应的升级服务器，公网上我就知道sohu的。
1.1备份CentOS-Base.repo
cd /etc/yum.repos.d/
cp CentOS-Base.repo CentOS-Base.repo.bak
1.2替换源 （以sohu更新源为例子）
用vi打开CentOS-Base.repo，并将内容清空，然后将下面的内容复制进去，并保存。
# 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-$releasever - Base
baseurl=http://mirrors.sohu.com/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.sohu.com/centos/RPM-GPG-KEY-CentOS-5
#released updates
[updates]
name=CentOS-$releasever - Updates
baseurl=http://mirrors.sohu.com/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.sohu.com/centos/RPM-GPG-KEY-CentOS-5
#packages used/produced in the build but not released
[addons]
name=CentOS-$releasever - Addons
baseurl=http://mirrors.sohu.com/centos/$releasever/addons/$basearch/
gpgcheck=1
gpgkey=http://mirrors.sohu.com/centos/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=http://mirrors.sohu.com/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.sohu.com/centos/RPM-GPG-KEY-CentOS-5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
baseurl=http://mirrors.sohu.com/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.sohu.com/centos/RPM-GPG-KEY-CentOS-5
1.3更新一下
yum -y update
2. 用yum升级安装Apache,Mysql,PHP.
Centos默认已安装相应的环境，但是版本可能达不到相关的要求。
A.安装部分
2.1安装Apache
yum install httpd httpd-devel
安装完成后，用/etc/init.d/httpd start 启动apache
设为开机启动:chkconfig httpd on
2.2 安装mysql
2.2.1 yum install mysql mysql-server mysql-devel
同样，完成后，用/etc/init.d/mysqld start 启动mysql
2.2.2设置mysql密码
mysql>; USE mysql;
mysql>; UPDATE user SET Password=PASSWORD('newpassword') WHERE user='root';
mysql>; FLUSH PRIVILEGES;
2.2.3 允许远程登录
mysql -u root -p
Enter Password: <your new password>
mysql>GRANT ALL PRIVILEGES ON *.* TO '用户名'@'%' IDENTIFIED BY '密码' WITH GRANT OPTION;
完成后就能用mysql-front远程管理mysql了。
2.2.4设为开机启动
chkconfig mysqld on
3. 安装php
yum install php php-mysql php-common php-gd php-mbstring php-mcrypt php-devel php-xml
/etc/init.d/httpd start
4. 测试一下
4.1 在/var/www/html/新建个test.php文件，将以下内容写入，然后保存。
<?
phpinfo();
?>
4.2 防火墙配置
a.添加.允许访问端口{21: ftp, 80: http}.
iptables -I RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 21 -j ACCEPT
iptables -I RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 80 -j ACCEPT
b.关闭防火墙{不推荐}.
service iptables stop
c.重置加载防火墙
service iptables restart
4.3 然后在客户端浏览器里打开http://serverip/test.php，若能成功显示，则表示安装成功。
至此，安装完毕。
参考：http://www.jb51.net/article/24775.htm
B 升级部分
1.选择合适的更新源
2.运行YUM UPDATE 查看更新源的软件相应版本
3.运行yum install ** 升级安装相应软件
