[gentoo-user] Network device name changes every reboot

[gentoo-user] Network device name changes every reboot

[Rennie deGraaf]

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Hello,

I'm running Gentoo x86/2006.1 inside a User-Mode Linux disk image, created
according to the instructions at
http://gentoo-wiki.com/HOWTO_User_Mode_Linux, with kernel 2.6.20.7 from
kernel.org.  The first time I booted my UML system, networking worked
properly.  The next time, net.eth0 failed to start.  Further investigation
revealed that /sys/class/net/eth0 didn't exist (despite entries in dmesg
indicating that it was being created).  However, /sys/class/net/eth1 *did*
exist, despite me not having specified a configuration for eth1 on the UML
command line.  I was able to successfully configure eth1 and communicate
with other hosts through it.

The next time I rebooted, eth1 had dissappeared, but there was now an eth2.
dmesg still contained references to /sys/class/net/eth0, but nothing about
eth2.  The next time, I got eth3.  And so on.  I rebuilt my UML image from
scratch, and got eth0 again on the first boot, but the device number kept
incrementing on further reboots.  I rebuilt the kernel with a few different
options, but that didn't affect the numbering.  I'm at eth12 now.

I have an older UML image based on kernel 2.6.16.16 and Gentoo 2006.0 from
last June or so; it doesn't display this behaviour.

I've double-checked that all UML-related processes have shut down completely
between reboots, and have deleted and re-created the tun/tap device on the
host system to ensure that the issue isn't with the host operating system.
The UML command line didn't change between boots.  Since the problem is
persistent across UML reboots, and changing the kernel didn't help, I'm
convinced that the issue lies with the Gentoo operating system in the UML
image.  Unfortunately, I have no idea what the problem is.

Does anyone have any idea what might be going on?  Any help would be greatly
appreciated.

Rennie deGraaf

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Re: [gentoo-user] Network device name changes every reboot

[Neil Bothwick]

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Hello Rennie deGraaf,

> I'm running Gentoo x86/2006.1 inside a User-Mode Linux disk image,
> created according to the instructions at
> http://gentoo-wiki.com/HOWTO_User_Mode_Linux, with kernel 2.6.20.7 from
> kernel.org.  The first time I booted my UML system, networking worked
> properly.  The next time, net.eth0 failed to start.  Further
> investigation revealed that /sys/class/net/eth0 didn't exist (despite
> entries in dmesg indicating that it was being created).
> However, /sys/class/net/eth1 *did* exist, despite me not having
> specified a configuration for eth1 on the UML command line.  I was able
> to successfully configure eth1 and communicate with other hosts through
> it.

I suspect that UML is assigning a different MAC address to your virtual
network interface each time it starts up.
/etc/udev/rules.d/70-persistent-net.rules ensures that each interface gets the same address on each boot, so you either need to ensure that UML uses the same MAC each time, or remove this file in /etc/conf.d/local.stop.


-- 
Neil Bothwick

Do PAL taglines take up two scanlines?

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