全新以最小化包安装了64位的CentOS6.3系统，作为本地的Web服务器使用，现记录全过程
第一步，配置并启用网上eth0

ifcfg-ethx网卡配置 文件路径，假设配置的是eth0网卡

[root@localhost ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0 #网卡设备名称
ONBOOT=yes #启动时是否激活 yes|no
BOOTPROTO=static #协议类型 dhcp bootp none
IPADDR=192.168.1.90 #网络IP地址
NETMASK=255.255.255.0 #网络子网地址
GATEWAY=192.168.1.1 #网关地址
BROADCAST=192.168.1.255 #广播地址
HWADDR=00:0C:29:FE:1A:09#网卡MAC地址
TYPE=Ethernet #网卡类型为以太网

:wq 保存配置
[root@localhost ~]#service network restart
发现居然报错如下，百思不得其解，只能baidu了
bringing up interface eth0 error ... device not managed by networkmanager or unavailable

最终百度到一个很离奇的解决方法，不明原理，望高人指点
解决办法：
1 chkconfig NetworkManager off
2 chkconfig network on
3 service NetworkManager stop
4 service network start

英文原文如下（大体意思是停掉NetworkManager，启用默认的Manager）：
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1. Remove Network Manager from startup Services.
chkconfig NetworkManager off
2. Add Default Net Manager
chkconfig network on
Stop NetworkManager first
service NetworkManager stop
and then start Default Manager
service network start
or you can change it easy:
system-config-network
uncheck the box that sets the eth0 as managed by NetworkManager and set IP info from there.
system-config-services
stop and disable NetworkManager , start and enable network
you have problem because both of NetworkManager and Network using same Network driver and default network blocking access for NetworkManager. if you disable NetworkManager your problem will disappeared after restart.