node failed to deploy because an ephemeral network device was not found

This bug was originally filed in Launchpad as [LP: #1931735](https://bugs.launchpad.net/cloud-init/+bug/1931735)

Launchpad details

affected_projects = ['maas']

assignee = None

assignee_name = None

date_closed = 2021-06-28T14:07:43.064776+00:00

date_created = 2021-06-11T17:56:55.509765+00:00

date_fix_committed = None

date_fix_released = None

id = 1931735

importance = undecided

is_complete = True

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1931735

milestone = None

owner = cgrabowski

owner_name = Christian Grabowski

private = False

status = opinion

submitter = axino

submitter_name = Junien Fridrick

tags = []

duplicates = []

_Launchpad user **Junien Fridrick(axino)** wrote on 2021-06-11T17:56:55.509765+00:00_

Hi,

Using MAAS snap 2.8.6-8602-g.07cdffcaa.

I just had a node failed to deploy because a network device that was present during commissioning wasn't present anymore, making cloud-init sad. To be precise, the node deployed properly, rebooted, and during the post-deploy boot, cloud-init got sad with :

RuntimeError: Not all expected physical devices present: {'be:65:46:cb:58:b7'}

(full stacktrace at https://pastebin.canonical.com/p/9Ycxwk5rRy/)

I was indeed able to find the network device with MAC address 'be:65:46:cb:58:b7', and it's an ephemeral NIC that gets created when someone logs in the HTML5 console (this is a Gigabyte server by the way). So someone was probably logged on the HTML5 console when the node was commissioned.

I deleted this ephemeral device from the node in MAAS, and was then able to deploy it properly.

These ephemeral NICs appear to have random MAC addresses. I was logged on the HTML5 console during the boot logged above, and you can see there's a device named "enx5a099ca01d4b" with MAC address "5a:09:9c:a0:1d:4b" (which doesn't match a known OUI).

This is actually a cdc_ether device :
$ dmesg|grep cdc_ether
[ 29.867170] cdc_ether 1-1.3:2.0 usb0: register 'cdc_ether' at usb-0000:06:00.3-1.3, CDC Ethernet Device, 5a:09:9c:a0:1d:4b
[ 29.867296] usbcore: registered new interface driver cdc_ether
[ 29.958137] cdc_ether 1-1.3:2.0 enx5a099ca01d4b: renamed from usb0
[ 205.908811] cdc_ether 1-1.3:2.0 enx5a099ca01d4b: unregister 'cdc_ether' usb-0000:06:00.3-1.3, CDC Ethernet Device

(the last time is very probably when I logged off the HTML5 console, which removes the device).

So I think :
- MAAS should ignore these devices by default
- cloud-init shouldn't die when a cdc_ether device is missing.

Thanks