Error: Connection activation failed: Device not managed by NetworkManager

在虚拟机中，启动eth0 网卡时报错：
Error: Connection activation failed: Device not managed by NetworkManager
于是在网上找了解决方法：
1. Remove Network Manager from startup Services.
#chkconfig NetworkManager off
2. Add Default Net Manager
#chkconfig network on
3.Stop NetworkManager first
#service NetworkManager stop
4.Start Default Manager
#service network start
提示：
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0: 
Determining IP information for eth0... done.
                                                           [  OK  ]
RTNETLINK answers: File exists
再重启一下网络就好了
service network restart