Nobody:nogroup ownership in unprivileged container

How did you add the disk to the instance

Nothing big lxc config device add c0 disks disk source=/disks/www path=/disks

Please can you show your full output of lxc config show --expanded?

Sure.

c0 (privileged)

config:
  image.architecture: amd64
  image.description: Debian buster amd64 (20210817_05:24)
  image.os: Debian
  image.release: buster
  image.serial: "20210817_05:24"
  image.type: squashfs
  image.variant: default
  security.nesting: "true"
  security.privileged: "true"
  volatile.base_image: 576fb563ea143ea03bffa97c40ccaaa13ca93c71d1be3135260aa1d6e258eddf
  volatile.eth0.host_name: veth9dedccb4
  volatile.eth0.hwaddr: 00:16:3e:2a:01:32
  volatile.idmap.base: "0"
  volatile.idmap.current: '[]'
  volatile.idmap.next: '[]'
  volatile.last_state.idmap: '[]'
  volatile.last_state.power: RUNNING
  volatile.uuid: eecc266c-8e3a-4c58-a854-928a4de2d907
  volatile.vmbr2.host_name: vethfee0440d
  volatile.vmbr2.hwaddr: 00:16:3e:99:f7:65
  volatile.vmbr2.name: eth1
devices:
  disks:
    path: /disks
    source: /disks/www
    type: disk
  eth0:
    ipv4.address: 192.168.2.99
    name: eth0
    nictype: bridged
    parent: vmbr2
    type: nic
  root:
    path: /
    pool: default
    type: disk
  vmbr2:
    nictype: bridged
    parent: vmbr2
    type: nic
ephemeral: false
profiles:
- default
stateful: false
description: ""

For C1 (unprivileged)

architecture: x86_64
config:
  image.architecture: amd64
  image.description: Debian buster amd64 (20210819_05:24)
  image.os: Debian
  image.release: buster
  image.serial: "20210819_05:24"
  image.type: squashfs
  image.variant: default
  volatile.base_image: fd7f927eccfe270452727e1c9bc145de7565cb84a8935806293ed42e8b0a8d34
  volatile.idmap.base: "0"
  volatile.idmap.current: '[{"Isuid":true,"Isgid":false,"Hostid":1000000,"Nsid":0,"Maprange":1000000000},{"Isuid":false,"I
sgid":true,"Hostid":1000000,"Nsid":0,"Maprange":1000000000}]'
  volatile.idmap.next: '[{"Isuid":true,"Isgid":false,"Hostid":1000000,"Nsid":0,"Maprange":1000000000},{"Isuid":false,"Isgi
d":true,"Hostid":1000000,"Nsid":0,"Maprange":1000000000}]'
  volatile.last_state.idmap: '[{"Isuid":true,"Isgid":false,"Hostid":1000000,"Nsid":0,"Maprange":1000000000},{"Isuid":false
,"Isgid":true,"Hostid":1000000,"Nsid":0,"Maprange":1000000000}]'
  volatile.last_state.power: RUNNING
  volatile.uuid: 87cf019e-a4fb-4cd0-8a08-9a8fe63c74e9
  volatile.vmbr0.host_name: vetha14c2ac7
  volatile.vmbr0.hwaddr: 00:16:3e:b9:28:81
  volatile.vmbr2.host_name: vethc0d0a72d
  volatile.vmbr2.hwaddr: 00:16:3e:bc:ec:31
  volatile.vmbr3.host_name: vethcd4a13a8
  volatile.vmbr3.hwaddr: 00:16:3e:4d:e5:b8
devices:
  disks:
    path: /disks
    source: /disks/www
    type: disk
  root:
    path: /
    pool: default
    type: disk
  vmbr0:
    ipv4.address: 10.x.x.x
    name: vmbr0
    nictype: bridged
    parent: vmbr0
    type: nic
  vmbr2:
    ipv4.address: 192.168.2.110
    name: vmbr2
    nictype: bridged
    parent: vmbr2
    type: nic
  vmbr3:
    ipv4.address: 192.168.3.110
    name: vmbr3
    nictype: bridged
    parent: vmbr3
    type: nic
ephemeral: false
profiles:
- default
stateful: false
description: ""