network-manager selects interface without cable attached

I have the same problem. In my case, the installer offered the extra D-Link card as the second option in its list (don't know if the ordering is relevant), and the installed system wanted to use the VIA card integrated onto the motherboard. The VIA card doesn' t have a cable attached, since it worked unreliably when I upgraded my home LAN to gigabit. I didn't bother to disable the integrated card in BIOS, to be able to easily swap between it and the D-Link card when testing.

Explicitly choosing the D-Link card in the NetworkManager applet made things work.

(This was with the 20070925.1 gutsy-alternate-i386.iso I'm testing today.)

Looks like NM is picking the wrong card on boot. Please read https://wiki.ubuntu.com/DebuggingNetworkManager and attach appropriate logs.

I followed the instructions on that page, and the syslog snippet is attached. I am not sure this is directly useful: after I manually chose the D-Link card, it seems to be chosen every time, even after a reboot. (Might be a timing problem, or udev randomness, rather than NM remembering the manual choice, though, for all I know.)

The snippet contains the entire syslog from the moment I did modprobe on the network card's driver.

I rebooted a few more times, to get more statistics, and NetworkManager does not always choose the same device: sometimes it chooses one, sometimes the other Ethernet card.

Lars, I don't understand the problem here. Given that NetworkManager is independent of ifupdown, how should NM know which interface you initially want to be upped?

Wearing a "ignorant user" hat: the installer asks me which interface should be used, but the installed system ignores that. I have to choose the right card from the NetworkManager every time, and that's pretty annoying. If NetworkManager in the installed system can't make use of the information I give the installer, at least NetworkManager should remember what I tell it directly.

Wearing a hat indicating slightly less ignorance: Why does NM choose an interface that doesn't have a signal over one that does? And why does it choose a different interface randomly rather than systematically?

There was some discussion about this on IRC, and as a result I was directed to look at /etc/udev/rules.d/70-persistent-net.rules, which I attach. Two things:

1) It names the interfaces eth2 and eth3, instead of eth0 and eth1, which is going to surprise a number of people.

2) If I switch the names around, it seems to get the right interface (D-Link, r8169) every time I test. If I keep them as they are in the file now, it never gets the right one. This could indicate that whatever sets up the rules file should put the interface the user prefers in the installer as the first one.

I assume this makes it a bug in the installer, not in NetworkManager, but as I'm new to Ubuntu, I'll let someone else make that decision.

Lars, did you already defined what the "right interface" is?

Anyway, I see 3 issues here (please correct me or add more):

 1. network-manager does select an interface without a signal
 2. network-manager appears to connect to random interfaces, which could or could not be caused by 1.
 3. ubuntu-installer (i think alternate install that is) asks the user for an interface to use during install, but doesn't mention that this will only be used during install if network-manager is going to be installed.

Which issue should be tracked in this bug? Please file bugs for the other issues.

Thanks,
 - Alexander

Alexander, I thought I did that already in my first message to this bug report: the D-Link card (r8169 driver, MAC 00:17:9a:3a:c9:52) is the right one, the VIA card is the wrong one (and has no cable attached).

That's also what I tell the installer, of course.

https://bugs.edge.launchpad.net/ubuntu/+source/udev/+bug/145382 may be relevant for my case.

Wrt point 3) I don't think it is unreasonable to assume that the default interface chosen in the installer will also be the default interface in the installed system. So probably the installer should write persistent-net.rules, not udev at the first boot.

OK, lets use this bug for 1. then. 3. is an installer issue and network-manager has no chance to know which one to use.

Lars, your syslog log gets an IP through you via card, which definitly doesn't capture the bug "interface selected though no cable attached" ... can you get a syslog for that testcase please.

Thanks,

 - Alexander

... and please open a new bug for the installer and attach the info about the .rules file et al.

Please post the bug id you use for that issue.

Thanks,

 - Alexander

... oh forgot. if bug 134496 covers the installer issue mentioned by Martin, you won't need to open a bug for that of course.

We are closing this bug report because it lacks the information we need to investigate the problem, as described in the previous comments. Please reopen it if you can give us the missing information, and don't hesitate to submit bug reports in the future. To reopen the bug report you can click on the current status, under the Status column, and change the Status back to "New". Thanks again!