我在一台双网卡工控机上装了Ubuntu server，断电开机之后，ifconfig -a只能看到一个网口。lshw -class network 发现第二个网口没有logic name。如下：
*-network
description: Ethernet interface
product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
vendor: Realtek Semiconductor Co., Ltd.
physical id: 0
bus info: pci@0000:03:00.0
logical name: p1p1
version: 06
serial: 00:0b
a8:9e:94size: 1Gbit/s
capacity: 1Gbit/s
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=full firmware=rtl8168e-3_0.0.4 03/27/12 ip=192.168.100.201 latency=0 link=yes multicast=yes port=MII speed=1Gbit/s
resources: irq:89 ioport:d000(size=256) memory:90604000-90604fff memory:90600000-90603fff
*-network UNCLAIMED
description: Ethernet controller
product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
vendor: Realtek Semiconductor Co., Ltd.
physical id: 0
bus info: pci@0000:04:00.0
version: 06
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress msix vpd cap_list
configuration: latency=0
resources: ioport:2000(size=256)
热重启之后，双网卡就都能使用了。请问是为什么？
这几天一直在研究这个问题。查看了Ubuntu 的官方文档，说是要修改/etc/udev/rules.d/70-persistent-net.rules文件，但是我发现我的系统里根本没有这个文件。又查出说是/lib/udev/write_net_rules 生成的文件。所以直接运行write_net_rules，又报missing $INTERFACE。
始终搞不懂Ubuntu是怎么设置网络的，请大神答疑解惑。