重启网卡提示：device not managed by networkmanager or unavailable

在虚拟机上把原有的网卡配置（桥接）更改成NAT模式，并修改/etc/sysconfig/network-scripts下的配置文件后
各种重启网卡，IP地址一直不按照配置文件变动，提示：
device not managed by networkmanager or unavailable
经百度：
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.
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http://blog.csdn.net/damaibao/article/details/8053528