VFS: Cannot open root device "LABEL=cloudimg-rootfs" or unknown-block(0,0): error -6

[Jason Hobbs]

Description
===========
An kvm instance failed to boot with a kernel panic after hitting this error:

VFS: Cannot open root device "LABEL=cloudimg-rootfs" or unknown-block(0,0): error -6

Steps to reproduce
==================
This doesn't reproduce reliably, it seems to be a race condition.

* I started an instance through the API. It had not attached storage, and was attached to a single network. It used an Ubuntu Xenial cloud image which booted successfully on a different instance on a different compute node.

Expected Result
===============
* I expected the instance to boot successfully

Actual Result
=============
* The instance failed to boot with a kernel panic:
http://pastebin.ubuntu.com/23911493/

* I used virsh destroy to stop that instance, then started it again through the API, and it worked.

Environment
===========
xenial/newtown/kvm/openvswitch, no attached storage.

ii nova-common 2:14.0.1-0ubuntu1~cloud0 all OpenStack Compute - common files
ii nova-compute 2:14.0.1-0ubuntu1~cloud0 all OpenStack Compute - compute node base
ii nova-compute-kvm 2:14.0.1-0ubuntu1~cloud0 all OpenStack Compute - compute node (KVM)
ii nova-compute-libvirt 2:14.0.1-0ubuntu1~cloud0 all OpenStack Compute - compute node libvirt support
ii python-nova 2:14.0.1-0ubuntu1~cloud0 all OpenStack Compute Python libraries
ii python-novaclient 2:6.0.0-0ubuntu1~cloud0 all client library for OpenStack Compute API - Python 2.7
ii libvirt-bin 1.3.1-1ubuntu10.6 amd64 programs for the libvirt library
ii libvirt0:amd64 1.3.1-1ubuntu10.6 amd64 library for interfacing with different virtualization systems
ii nova-compute-libvirt 2:14.0.1-0ubuntu1~cloud0 all OpenStack Compute - compute node libvirt support
ii python-libvirt 1.3.1-1ubuntu1 amd64 libvirt Python bindings

[Christian Ehrhardt  (paelzer)]

Seems like a race in populating and using the labels on the disks (or an I/O error, but I haven't found one in the log).
In any case I think this should get to the attention of the kernel Team.

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1661292

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Brant Gardner (brantcgardner)]

I'm on AWS EC2 rather than OpenStack, but I am getting this exact error on a t1.micro Ubuntu 16.04.2 LTS box.

Starting with the most recent set of kernel updates the box did not return from the next reboot (or any reboot since).

Log:

http://pastebin.ubuntu.com/24229055/

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]

[Launchpad Janitor (janitor)]

[Expired for OpenStack Compute (nova) because there has been no activity for 60 days.]