故障现象：
最近在公司测试环境克隆了几个Linux系统，重启之后发现，网卡eth0都不见了
于是检查了网卡配置，最终想到以下几种解决方案，网卡启动信息如图所示：
[root@test3 ~]# service network restart
Shutting down loopback insterface: [ OK ]
Bringing up loopback insterface: [ OK ]
Bringing up interface eth0: Device eth0 does not seem to be present,delaying initialization. [FAILED]
方法一：
[root@test3 ~]# rm -rf /etc/udev/rules.d/70-persistent-net.rules
[root@test3 ~]# init 6
[root@test3 ~]# service network restart
Shutting down loopback insterface: [ OK ]
Bringing up loopback insterface: [ OK ]
Bringing up interface eth0: [ OK ]
方法二：
造成这样的原因，是因为在虚拟机（Vmware）中移动了Centos系统对应的文件
导致重新配置时，网卡的MAC地址变了，输入ifconfig -a,找不到eth0
安装完一个centos虚拟机，又拷贝一份，开机后网卡无法正常启动
报错：
Device eth0 does not seem to be present,
delaying initialization
解决：
[root@test3 ~]# cd /etc/sysconfig/network-scripts/
[root@test3 ~]# mv ifcfg-eth0 ifcfg-eth1
[root@test3 ~]# vim sysconfig/network-scripts/ifcfg-eth1
修改DEVICE="eth0"
为DEVICE="eth1"
[root@test3 ~]# service network restart
方法三：
故障前的操作：
DELL刀片装的是CentOS6.3的操作系统，网卡识别的是em1和em2，由于工作需要做了槽位调整，并启动了刀片
故障现象：
启动后网络不通，通过iDRAC登录后route查看缺省路由正常；
重启网络服务：
[root@test3 ~]# service network restart
Shutting down loopback insterface: [ OK ]Bringing up loopback insterface: [ OK ]Bringing up interface em1: Device em1 does not seem to be present,delaying initialization. [FAILED]分析问题和解决：
之前在别的文章中我们提过70-persistent-net.rules文件，所以看了一下：
[root@test3 ~]# vim /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.
# PCI device 0x14e4:0x163a (bnx2) SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="24:b6:fd:ab:76:1e", ATTR{type}=="1", KERNEL=="eth*", NAME="eth1"
# PCI device 0x14e4:0x163a (bnx2) SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="24:b6:fd:ab:76:1c", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"
发现NAME的名称不正确，依次将上述红色字体中的eth0改为em1，eth1改为em2；
*切记：网卡编号由MAC地址大小决定，MAC越小网卡编号越小；
如下：
# PCI device 0x14e4:0x163a (bnx2)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="24:b6:fd:ab:76:1e", ATTR{type}=="1", KERNEL=="eth*", NAME="em2"
# PCI device 0x14e4:0x163a (bnx2) SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="24:b6:fd:ab:76:1c", ATTR{type}=="1", KERNEL=="eth*", NAME="em1"
保存退出~！
[root@test3 ~]# init 6
问题解决~！