[lug] Debugging a startup problem

Lee Woodworth blug-mail at duboulder.com
Mon Jul 30 00:17:15 MDT 2018

RE: if renaming, with newer kernels+udev there is something
related to persistent interface naming where udev will rename
eth0 to a bus/slot/function related name (e.g. enps3). Do you
ever see names like that in dmesg? Is there a way see if any
systemd service/unit is renaming the interface? BTW udev appears
to have been taken over by systemd as the daemon binary is
/lib/systemd/systemd-udevd using the standard udev package.

When you say 'network doesn't come up', do you mean the nic's
link isn't detected, it doesn't have any addresses/routes or
it had a link and address but was shutdown? What happens when
you do: ip link set dev ethX up? (e.g. does it come up but
systemd or xxx then shuts it down)

bringing the interface up work (ip set dev=
On 07/29/2018 10:40 PM, Jed S. Baer wrote:
> On Sun, 8 Jul 2018 19:02:30 -0600
> Jed S. Baer wrote:
>> Symptom is that on a reboot, the network doesn't come up
> I finally revisited this, and don't have much extra to mention, except
> that I finally did the smart thing, and booted from a newer Ubuntu on a
> USB stick. The network comes right up.
> One odd thing I note is that after I disable avahi (using the override
> file method), the ethernet device is no longer being changed eth0->eth3,
> but to eth2, and it has a different MAC address.
> The fix is still to issue service network-manager start, or service
> network-manager restart, once the system comes up.
> Re-installing network manager didn't help.
> Deleting all the interfaces in the GUI, and re-adding the eth2 interface
> didn't help.
> Adding a stanza for eth2 in /etc/network/interfaces didn't help.
> I did learn a few things, none of which really get me closer to figuring
> out why the wired network won't come up.
> Maybe I need to tweek the file for the wired connection
> in /etc/NetworkManager/system-connections/ ??? Nothing in the nm-settings
> man page is suggestive, as the only thing that seems relevant is the
> autoconnect, but that defaults to TRUE.
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