原文地址：http://bbs.chinaunix.net/thread-1918368-1-1.html
环境：Virtualbox+RHEL 6 x64
用VirtualBox的vboxmanager克隆的虚拟机，操作系统RHEL6，启动后发现网卡不能用了。重启网络服务，报以下错误:
Bringing up interface eth0: Device eth0 does not seem to be present, delaying initialization. [FAILED]
在RHEL5里也发生类似事情，因为复制虚拟机MAC会重新生成，但是操作系统的MAC却写在ifcfg-ethx里，造成了不一致，所以不能启动网络接口，在RHEL5里可以使用kudzu或者注释网卡配置文件的MAC字段来解决这个问题。但是在RHEL6里，kudzu已经被hal服务取代了。虽然lspci能够正常认到网卡，但是却无法使用/etc/init.d/network restart来启动服务。尝试注释ifcfg-eth0的MAC字段，还是报错。查看了下udev的规则，发现了问题的所在。
[root@Oracle ~]# cat /etc/udev/rules.d/70-persistent-net.rules
# This file was automatically generated by the /lib/udev/write_net_rules
# program, run by the persistent-net-generator.rules rules file.
#
# You can modify it, as long as you keep each rule on a single
# line, and change only the value of the NAME= key.
# net device () (custom name provided by external tool)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="08:00:27:16:31:11", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"
# net device ()
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="08:00:27:32:66:63", ATTR{type}=="1", KERNEL=="eth*", NAME="eth1"
[root@Oracle ~]#
原来UDEV这里把克隆前的MAC当成了当前虚拟机的eth0 MAC，而重新生成的08:00:27:32:66:63是eth1的MAC。
解决这个问题，只要删除旧的UDEV配置，修改为：
[root@Oracle ~]# cat /etc/udev/rules.d/70-persistent-net.rules
# This file was automatically generated by the /lib/udev/write_net_rules
# program, run by the persistent-net-generator.rules rules file.
#
# You can modify it, as long as you keep each rule on a single
# line, and change only the value of the NAME= key.
# net device () (custom name provided by external tool)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="08:00:27:32:66:63", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"
重启network服务，一切OK
[root@Oracle ~]# /etc/init.d/network restart
Shutting down interface eth0: [ OK ]
Shutting down loopback interface: [ OK ]
Bringing up loopback interface: [ OK ]
Bringing up interface eth0: [ OK ]
[root@Oracle ~]# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 08:00:27:32:66:63
inet addr:172.16.100.3 Bcast:172.16.100.255 Mask:255.255.255.0
inet6 addr: fe80::a00:27ff:fe32:6663/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:206 errors:0 dropped:0 overruns:0 frame:0
TX packets:203 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:21157 (20.6 KiB) TX bytes:24515 (23.9 KiB)