VM not starting 'warning: failed to register linux io_uring ring file descriptor'

VM failing to start with ‘warning: failed to register linux io_uring ring file descriptor’ error

What LXD version, on what Linux distribution, on what kernel and using what kind of package?

lxd; 5.8
linux: Ubuntu 20.04.5 LTS
kernel: Kernel: Linux 5.14.0-1054-oem

Was reopening a stateful win11

Does that happen with new VMs too or just with reopening that one?
Can you show snap info lxd?

No just happened to this one;

name: lxd
summary: LXD - container and VM manager
publisher: Canonical✓
store-url: Install lxd on Linux | Snap Store
contact: Issues · lxc/lxd · GitHub
license: unset
description: |
LXD is a system container and virtual machine manager.

It offers a simple CLI and REST API to manage local or remote instances,
uses an image based workflow and support for a variety of advanced features.

Images are available for all Ubuntu releases and architectures as well
as for a wide number of other Linux distributions. Existing
integrations with many deployment and operation tools, makes it work
just like a public cloud, except everything is under your control.

LXD containers are lightweight, secure by default and a great
alternative to virtual machines when running Linux on Linux.

LXD virtual machines are modern and secure, using UEFI and secure-boot
by default and a great choice when a different kernel or operating
system is needed.

With clustering, up to 50 LXD servers can be easily joined and managed
together with the same tools and APIs and without needing any external
dependencies.

Supported configuration options for the snap (snap set lxd [=…]):

- ceph.builtin: Use snap-specific Ceph configuration [default=false]
- ceph.external: Use the system's ceph tools (ignores ceph.builtin) [default=false]
- criu.enable: Enable experimental live-migration support [default=false]
- daemon.debug: Increase logging to debug level [default=false]
- daemon.group: Set group of users that have full control over LXD [default=lxd]
- daemon.user.group: Set group of users that have restricted LXD access [default=lxd]
- daemon.preseed: Pass a YAML configuration to `lxd init` on initial start
- daemon.syslog: Send LXD log events to syslog [default=false]
- daemon.verbose: Increase logging to verbose level [default=false]
- lvm.external: Use the system's LVM tools [default=false]
- lxcfs.pidfd: Start per-container process tracking [default=false]
- lxcfs.loadavg: Start tracking per-container load average [default=false]
- lxcfs.cfs: Consider CPU shares for CPU usage [default=false]
- openvswitch.builtin: Run a snap-specific OVS daemon [default=false]
- openvswitch.external: Use the system's OVS tools (ignores openvswitch.builtin) [default=false]
- ovn.builtin: Use snap-specific OVN configuration [default=false]
- shiftfs.enable: Enable shiftfs support [default=auto]

For system-wide configuration of the CLI, place your configuration in
/var/snap/lxd/common/global-conf/ (config.yml and servercerts)
commands:

  • lxd.benchmark
  • lxd.buginfo
  • lxd.check-kernel
  • lxd.lxc
  • lxd.lxc-to-lxd
  • lxd
  • lxd.migrate
    services:
    lxd.activate: oneshot, enabled, inactive
    lxd.daemon: simple, enabled, active
    lxd.user-daemon: simple, enabled, inactive
    snap-id: J60k4JY0HppjwOjW8dZdYc8obXKxujRu
    tracking: latest/stable
    refresh-date: yesterday at 20:36 GMT
    channels:
    latest/stable: 5.7-c62733b 2022-10-29 (23889) 143MB -
    latest/candidate: 5.8-bb9c9b1 2022-11-22 (23983) 143MB -
    latest/beta: ↑
    latest/edge: git-da8b2f6 2022-11-22 (24015) 143MB -
    5.8/stable: –
    5.8/candidate: 5.8-bb9c9b1 2022-11-22 (23983) 143MB -
    5.8/beta: ↑
    5.8/edge: ↑
    5.7/stable: 5.7-c62733b 2022-10-29 (23889) 143MB -
    5.7/candidate: 5.7-2d1f249 2022-11-01 (23908) 143MB -
    5.7/beta: ↑
    5.7/edge: ↑
    5.6/stable: 5.6-794016a 2022-09-27 (23680) 142MB -
    5.6/candidate: 5.6-794016a 2022-09-23 (23680) 142MB -
    5.6/beta: ↑
    5.6/edge: ↑
    5.0/stable: 5.0.1-9dcf35b 2022-08-24 (23541) 107MB -
    5.0/candidate: 5.0.1-789b883 2022-11-22 (24002) 115MB -
    5.0/beta: ↑
    5.0/edge: git-13e1e53 2022-11-22 (23982) 115MB -
    4.0/stable: 4.0.9-8e2046b 2022-03-26 (22753) 71MB -
    4.0/candidate: 4.0.9-eb5e237 2022-11-22 (23991) 96MB -
    4.0/beta: ↑
    4.0/edge: git-407205d 2022-11-22 (23988) 96MB -
    3.0/stable: 3.0.4 2019-10-10 (11348) 55MB -
    3.0/candidate: 3.0.4 2019-10-10 (11348) 55MB -
    3.0/beta: ↑
    3.0/edge: git-81b81b9 2019-10-10 (11362) 55MB -
    installed: 5.8-ee04373 (23972) 143MB -

Okay, can you also show those two, right after a lxc start failure:

  • dmesg | tail -n 30
  • lxc info --show-log NAME

[169777.031769] lxdbr0: port 1(tapd820d563) entered blocking state
[169777.031778] lxdbr0: port 1(tapd820d563) entered disabled state
[169777.031928] device tapd820d563 entered promiscuous mode
[169777.114058] audit: type=1400 audit(1669121887.770:354): apparmor=“STATUS” operation=“profile_replace” info=“same as current profile, skipping” profile=“unconfined” name=“lxd-win11_</var/snap/lxd/common/lxd>” pid=778196 comm=“apparmor_parser”
[169777.123188] audit: type=1400 audit(1669121887.778:355): apparmor=“DENIED” operation=“open” profile=“lxd-win11_</var/snap/lxd/common/lxd>” name="/var/lib/snapd/hostfs/run/systemd/resolve/stub-resolv.conf" pid=778197 comm=“lxd” requested_mask=“r” denied_mask=“r” fsuid=0 ouid=101
[169777.396054] lxdbr0: port 1(tapd820d563) entered blocking state
[169777.396069] lxdbr0: port 1(tapd820d563) entered forwarding state
[169778.028465] lxdbr0: port 1(tapd820d563) entered disabled state
[169778.100555] device tapd820d563 left promiscuous mode
[169778.100574] lxdbr0: port 1(tapd820d563) entered disabled state
[169903.862529] lxdbr0: port 1(tapc1d8c513) entered blocking state
[169903.862543] lxdbr0: port 1(tapc1d8c513) entered disabled state
[169903.862704] device tapc1d8c513 entered promiscuous mode
[169903.972927] audit: type=1400 audit(1669122014.630:356): apparmor=“STATUS” operation=“profile_replace” info=“same as current profile, skipping” profile=“unconfined” name=“lxd-win11_</var/snap/lxd/common/lxd>” pid=778709 comm=“apparmor_parser”
[169903.983671] audit: type=1400 audit(1669122014.642:357): apparmor=“DENIED” operation=“open” profile=“lxd-win11_</var/snap/lxd/common/lxd>” name="/var/lib/snapd/hostfs/run/systemd/resolve/stub-resolv.conf" pid=778710 comm=“lxd” requested_mask=“r” denied_mask=“r” fsuid=0 ouid=101
[169904.259399] lxdbr0: port 1(tapc1d8c513) entered blocking state
[169904.259411] lxdbr0: port 1(tapc1d8c513) entered forwarding state
[169904.880142] lxdbr0: port 1(tapc1d8c513) entered disabled state
[169904.958583] device tapc1d8c513 left promiscuous mode
[169904.958601] lxdbr0: port 1(tapc1d8c513) entered disabled state
[171948.157445] lxdbr0: port 1(tape6297481) entered blocking state
[171948.157454] lxdbr0: port 1(tape6297481) entered disabled state
[171948.157601] device tape6297481 entered promiscuous mode
[171948.307995] audit: type=1400 audit(1669124058.966:358): apparmor=“STATUS” operation=“profile_replace” info=“same as current profile, skipping” profile=“unconfined” name=“lxd-win11_</var/snap/lxd/common/lxd>” pid=783987 comm=“apparmor_parser”
[171948.317120] audit: type=1400 audit(1669124058.974:359): apparmor=“DENIED” operation=“open” profile=“lxd-win11_</var/snap/lxd/common/lxd>” name="/var/lib/snapd/hostfs/run/systemd/resolve/stub-resolv.conf" pid=783988 comm=“lxd” requested_mask=“r” denied_mask=“r” fsuid=0 ouid=101
[171948.594871] lxdbr0: port 1(tape6297481) entered blocking state
[171948.594886] lxdbr0: port 1(tape6297481) entered forwarding state
[171949.165102] lxdbr0: port 1(tape6297481) entered disabled state
[171949.302374] device tape6297481 left promiscuous mode
[171949.302395] lxdbr0: port 1(tape6297481) entered disabled state

Name: win11
Status: STOPPED
Type: virtual-machine
Architecture: x86_64
Created: 2022/10/17 22:47 GMT
Last Used: 2022/11/21 17:20 GMT

Snapshots:
±----------------±---------------------±-----------±---------+
| NAME | TAKEN AT | EXPIRES AT | STATEFUL |
±----------------±---------------------±-----------±---------+
| uber-yango-bolt | 2022/10/22 09:16 GMT | | NO |
±----------------±---------------------±-----------±---------+
| whatsappbiz | 2022/10/19 13:10 GMT | | NO |
±----------------±---------------------±-----------±---------+

Log:

warning: failed to register linux io_uring ring file descriptor

lxc start win11

Error: open /var/snap/lxd/common/lxd/virtual-machines/win11/state: no such file or directory
Try lxc info --show-log win11 for more info

That part is odd, but I don’t know how that would be related to iouring.
I’ll have to see if I can reproduce the issue locally, that was a VM you did lxc stop --stateful vm11 and are now trying to lxc start win11?

Yes

Okay. If you need it back quickly, lxc start --stateless win11 should work but will discard the saved state.

That will suffice. Working fine. Much appreciated!