Bringing up interface eth0: Device eth0 does not seem to be present, delaying initialization

Why Does My Linux VM’s Virtual NIC Show Up As eth1?

by Bob Plankers on November 1, 2011 · 12 comments

in System Administration, Virtualization

 

Got a Red Hat Enterprise Linux (or CentOS, or Scientific Linux, or Oracle Enterprise Linux, etc.) 6 VM that won’t bring up it’s single network interface after you clone it?

Get the following error when you try using /sbin/ifup to enable it?

"Device eth0 does not seem to be present, delaying initialization."

 When you use “/sbin/ifconfig -a” you see eth1 where eth0 should be?

eth1      Link encap:Ethernet  HWaddr 00:50:56:9B:00:85  
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:812 errors:0 dropped:0 overruns:0 frame:0
          TX packets:214 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:72509 (70.8 KiB)  TX bytes:28324 (27.6 KiB)
lo        Link encap:Local Loopback 
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

 

What the heck?

It’s the udev persistent network interface rules. If you delete /etc/udev/rules.d/70-persistent-net.rules it’ll rebuild them during the next boot, based on the current state of the host, and you’ll get eth0 back. You can also edit it to change the list of MAC addresses. 

There are a couple of ways to disable this functionality permanently.

1. You can remove /lib/udev/rules.d/75-persistent-net-generator.rules. The problem with this approach is that when there’s an update to udev it’ll likely replace the file again and recreate the problem.

2. You could make it part of your machine cloning process, or template prep. All that does is set yourself up for potential problems later, though. Like when you’re on vacation and the new guy clones an already-running VM. Or you do, and you’ve forgotten about this problem… :)

3. You could hijack the rule in /lib/udev/rules.d/75-persistent-net-generator.rules that creates this stuff:

KERNEL!="eth*|ath*|wlan*[0-9]|msh*|ra*|sta*|ctc*|lcs*|hsi*", GOTO="persistent_net_generator_end"

Invert the logic by changing the “!=” to a “==” so it always skips eth* (and everything else in the list):

KERNEL=="eth*|ath*|wlan*[0-9]|msh*|ra*|sta*|ctc*|lcs*|hsi*", GOTO="persistent_net_generator_end"

You could also remove just eth* from the list if you still wanted to preserve the behavior for other interfaces:

KERNEL!="ath*|wlan*[0-9]|msh*|ra*|sta*|ctc*|lcs*|hsi*", GOTO="persistent_net_generator_end"

This is what I’m doing. I’m hoping that Red Hat does the right thing during a patch by recognizing that the file is changed and not overwriting it.

 

Update: Read the comments. Lars left a good one, set the 70-persistent-net.rules file to immutable. Also, he reminded me that RPM will tell you what files are config files, if you ask it. :) Thanks man.

原文来自： http://lonesysadmin.net/2011/11/01/why-does-my-linux-vms-virtual-nic-show-up-as-eth1/