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Re: how to compute predictable network interface names?



On Thu, Feb 16, 2017 at 12:47:25PM +0100, Christian Seiler wrote:
> On a system with predictable names running? Or on a system
> pre-upgrade?
> 
> Because if you have a system that's being upgraded at the
> moment, the following command _might_ work _after_ you've
> upgraded udev and _before_ you've rebooted the system.
> 
> udevadm info /sys/class/net/eth4
> 
> Look at ID_NET_NAME there.
> 
> Can't really test that though, since I don't have a setup
> with the old scheme that I still need to upgrade, so this
> might not work at all.

I'm a bit confused here.  On a system that's upgraded from jessie to
stretch, why would the interface names change at all?  The old eth0
style names are recorded in /etc/udev/rules.d/70-persistent-net.rules
and the interfaces continue to come up as eth0, etc.

Are you talking about a scenario where you upgrade to stretch and then
add a new NIC?  But even then it still wouldn't make sense, because
you wouldn't have had a previous "eth4" name that you want to map to a
new name.  You'd just get the new name.

Or are you talking about a hypothetical scenario where you upgrade to
stretch and then remove the contents of
/etc/udev/rules.d/70-persistent-net.rules, but before you do that, you
want to see what the interfaces will become?  That seems... quite odd
to me.  Why not just leave the interfaces alone?


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