Netplan and udevadm broken in Ubuntu 22 containers

[spockdude]

The physical host is running 18.04.6 LTS and LXD/LXC 3.0.3. I have two unprivileged containers, one Ubuntu 18.04 container and a new Ubuntu 22.04 container. (Using the default images that lxc launch provides.)

netplan works fine in the Ubuntu 18.04 container, but due to udevadm trigger returning errors in the Ubuntu 22.04 container (which netplan relies on), netplan fails there.

Running netplan apply gives me the following errors:

eth0: Failed to write 'change' to '/sys/devices/virtual/net/eth0/uevent': Permission denied
...etc...
subprocess.CalledProcessError: Command '['udevadm', 'trigger', '--attr-match=subsystem=net']' returned non-zero exit status 1.

It seems that the root of the problem is that udevadm trigger is busted.

I’m a little puzzled how such a basic feature such as netplan could be broken. Does nobody use netplan inside of a container using Ubuntu 22 under a physical host running Ubuntu 18? Ubuntu 18 containers running on the same physical host have no issues running netplan.

The issue I’m running into appears to be the same issue experienced here:

No IPv4 on Arch Linux containers

Just wanted to give an update in this thread as we now think we fully understand the problem. The regression was indeed introduced through a bugfix in systemd 244.1 as linked in the post above. The systemd developers refused to back this change to fix our users arguing that the new logic is correct and that the problem is that /sys is writable in our containers. We can’t make /sys read-only as we specifically need it writable for a number of other network operations (bridges for libvirt and t…

I have tried the things discussed in the above conversation.

Creating this file in the container:

/etc/systemd/system/systemd-networkd.service.d/lxc.conf:

[Service]
BindReadOnlyPaths=/sys

Tried adding this to the container configs:

lxc.mount.auto: sys

And later this:

lxc.mount.auto = proc:rw sys:ro

I also tried setting security.nesting to “true”.

None of this seems to help.

I see another user experiencing a similar issue with using netplan in a Ubuntu 22 LXC container here:

Unable to utilize wireless adapter in a container

Hello, I have a host running Ubuntu 22.04LTS and I am running an LXC container, also utilizing the Ubuntu 22.04 image. I am trying to make use of a USB wireless adapter within a LXC container. I have added the following in the LXC container profile: wlx00ef44fc4085: name: wlx00ef44fc4085 nictype: physical parent: wlx00ef44fc4085 type: nic This allows that USB wireless adapter to be recognized within the LXC container via " ip link " / " ip address " output. Within the LXC container (a U…

It seems they just gave up on netplan after nobody was able to offer any solutions. That seems like what I’ll end up doing too. Just a bummer since I have systems that relied on netplan and now those systems will need to be altered to bypass netplan.

I can get the Ubuntu 22 container on the network by manually running ip addr add, etc. but not with netplan. So, I have a workaround, but I would prefer to see a fix for netplan.

Possibly related: "udevadm trigger" fails in containers with ro /sys · Issue #14060 · systemd/systemd · GitHub