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How do I get Ubuntu to figure out the interfaces available on my computer and generate a new /etc/network/interfaces file? It created it the first time so I know it can somehow.

Is there something like dpkg-reconfigure <what?> that would just recheck for me?

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What would you want this for? – Zoredache Jul 1 '10 at 1:35
I'm +1-ing this question because we need non-linux people to be able to configure networks for our appliance. Something e.g. curses based that makes it easy is what I'm looking for... – Peter V. Mørch Jan 13 '12 at 9:53

in ubuntu 14.04.1 THIS happens if you clone a system to other hardware as /etc/udev/rules.d/70-persistent-net.rules contains MAC address's of ethernet hardware on the source computer.

YES - just deleting /etc/udev/rules.d/70-persistent-net.rules allows things to be refreshed to a working state at reboot.

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/etc/network/interfaces is generated by the actual installer, not any of the packages on your system:

opus:~ broder$ dpkg -S /etc/network/interfaces
dpkg: /etc/network/interfaces not found.

Because it's not managed by any particular package, no package is going to modify the file.

If you want to add new interfaces to /etc/network/interfaces, you have to do that manually. Alternatively, if you want your network interfaces to be managed automatically by your system, I believe the official answer at this point is to use NetworkManager. NetworkManager will handle configuration for any network interface that's not listed in /etc/network/interfaces.

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dpkg-reconfigure ifupdown


However, you are probably running into an issue with udev. If you have rebooted, and eth0 disappeared:

ifconfig -a

you can mv/rm the file in /etc/udev/rules.d/70-persistent-net.rules and reboot, and your primary ethernet card should become eth0 again.

This would happen if you switched motherboards/network cards.

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