VirtualBox加载存在CentOS虚拟机网卡无法加载

VirtualBox加载存在CentOS虚拟机网卡无法加载最可能的原因是：

你的虚拟网卡的Mac地址被更改了，系统保留了eth0，为新mac地址的生成eth1或其他名字的网卡配置.启动报告错误为：
Bringing up interface eth0: Device eth0 does not seem to be present, delaying initialization.


解决办法是：
步骤I. 修改/etc/udev/rules.d/70-persistent-net.rules 文件

# PCI device 0x8086:0x100e (e1000) (custom name provided by external tool)
#SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*",ATTR{address}=="08:00:27:0e:c0:8d", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"

# PCI device 0x8086:0x100e (e1000)
#SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*",ATTR{address}=="08:00:27:21:5e:05", ATTR{type}=="1", KERNEL=="eth*", NAME="eth1"

# PCI device 0x8086:0x100e (e1000)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="08:00:27:90:53:88", ATTR{type}=="1", KERNEL=="eth*", NAME="eth2"
~

如上面的示例，将eth0行注释，将最后一项的NAME="eth2"修改为NAME="eth0"，存盘退出。

步骤II. 修改/etc/sysconfig/network-scripts/ifcfg-eth0
将行HWADDR=08:00:27:0e:c0:8d修改为HWADDR=08:00:27:90:53:88
否则会重启网卡会提示：
Bringing up interface eth0: Device eth0 has different MAC address than expected.

存盘退出，重新启动网卡：service network restart就OK了

方法II
前提：克隆时选择Reinitialize the MAC address of all network cards
启动后：
1. 删除 /etc/udev/rules.d/70-persistent-net.rules
2. 删除 /etc/sysconfig/network-scripts/ifcfg-eth0 （最好重改名）
3. 重新启动服务器，然后重建ifcfg-eth0（使用新的mac address）