开启虚拟机莫名其妙就PING不通了，启动网卡时报以下错：

Bringing up interface eth0:  Error: Connection activation failed: Device not managed by NetworkManager or unavailable

                                                          [FAILED]

RTNETLINK answers: File exists

RTNETLINK answers: File exists

RTNETLINK answers: File exists

RTNETLINK answers: File exists

RTNETLINK answers: File exists

RTNETLINK answers: File exists

RTNETLINK answers: File exists

RTNETLINK answers: File exists

RTNETLINK answers: File exists

于是关闭NetworkManager:

#service NetworkManager stop

再修改网卡的配置文件：

#vim /etc/sysconfig/network-scripts/ifcfg-eth0

将M_CONTROLLED=NO改为YES

重启网卡后正常

原因应该是NetworkManager服务与network服务冲突千万的