ns.GetNS - unknown FS magic on "/run/snap.docker/netns/{container_id}": 1021994

[jocado]

Hi,

This isn't necessarily a bug as such, but I'm trying to get a bit more info on the failing mechanism to see if there is any way I can at least work around it, or even better perhaps contribute a fix somewhere.

When using CNI plugins with Nomad, and docker running from a snap, it results in the following error pattern when creating the container via Nomad:

failed to setup alloc: pre-run hook "network" failed: failed to configure networking for alloc: failed to configure network: plugin type="bridge1" failed (add): failed to open netns "/run/snap.docker/netns/db65a7df22ec": unknown FS magic on "/run/snap.docker/netns/db65a7df22ec": 1021994

The bridge1 plugin referred to here is identical to the referenced in the workaround here: https://github.com/hashicorp/nomad/issues/11085

#!/bin/bash
CNI_IFNAME=eth1
exec /opt/cni/bin/ipvlan

I've tried this with both CNI plugin bundle versions 1.3.0 and 1.6.0

Nomad [ which is also running from a snap ], works fine for standard docker operations.

I have tried running the nomad process with the snap confinement disabled [ apparmor and seccomp ], but get the same error. I'm wondering if there is some kind of mount namespace issue going on, but it's not clear because the contents of /run/snap.docker/netns/ is isn't itself in a separate mount namespace.

Is anyone able to tell me where I should start looking ? What is the likely cause of unknown FS magic ?

It seems like there is some kind of mount info somewhere which can't be access from nomad,. Just not sure where.

Thanks very much!

Cheers, Just