LVM storage pool setup using an existing volume group with LXD

This tutorial covers clearing an existing partition (/dev/sda4) which contains a volume group with a single logical volume and a mounted filesystem on it, and configuring a fresh volume group using the existing partition and 3 additional disks (/dev/sda, /dev/sdb and /dev/sdc) for use as a LXD storage pool.

Clear existing logical volume(s) (if needed)

In my host I had setup an existing logical volume mounted on /home, called ‘all’ and gave it all remaining space (with 30GB for the ubuntu 20 system on a separate partition).

loop0        7:0    0   62M  1 loop /snap/core20/1611
loop1        7:1    0 67.8M  1 loop /snap/lxd/22753
loop2        7:2    0   47M  1 loop /snap/snapd/16292
sda          8:0    0  1.8T  0 disk 
├─sda1       8:1    0  511M  0 part /boot/efi
├─sda2       8:2    0    3G  0 part /
├─sda3       8:3    0  512M  0 part [SWAP]
├─sda4       8:4    0  1.8T  0 part 
│ └─vg-all 253:0    0  1.8T  0 lvm  /home
└─sda5       8:5    0    2M  0 part 
sdb          8:16   0  1.8T  0 disk 
sdc          8:32   0  1.8T  0 disk 
sdd          8:48   0  1.8T  0 disk

You can see above /home (vg-all) is on sda4. and we want the vg to include that later with sdb, sdc and sdd.

So I’m now logged in as the default ubuntu user. So I set the passwds for ubuntu and root


nano /etc/ssh/sshd_config
add `PermitRootLogin yes`
service ssh reload

I next want to su as root and make sure mount /home never happens and ubuntu user wont be using it and blocking the command with something like ‘device busy’

nano /etc/fstab

Remove the line with /home in it so it wont be looked for to be mounted.


Login as root and see that /home is not mounted

umount /home
umount: /home: not mounted.

List lvs to show current LVM state:

  WARNING: Couldn't find device with uuid 7B1V6G-NVcM-4HMF-PFVO-RqJa-tH6P-urUXEM.
  WARNING: VG ALL is missing PV 7B1V6G-NVcM-4HMF-PFVO-RqJa-tH6P-urUXEM (last written to /dev/sda4).
  LV   VG Attr       LSize  Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  all  vg -wi-ao---- <1.82t

So I see above that the lv ‘all’ is in the folder ‘vg’.
So I can ls -l /dev/vg/all and see it there

Dissable the lv and delete it.

lvchange -an /dev/vg/all       # disable
lvremove /dev/vg/all           # delete

Create new volume group

Make sure no filesystem markers remain on any disks we want to join:

wipefs --all --force /dev/sdb
wipefs --all --force /dev/sdc
wipefs --all --force /dev/sdd
wipefs --all --force /dev/sda4

Now add the disks as physical volumes using pvs then join them together as a volume group vg called ‘ALL’:

pvcreate /dev/sda4 /dev/sdb /dev/sdc /dev/sdd
vgcreate ALL /dev/sda4 /dev/sdb /dev/sdc /dev/sdd

The vg should be ready for LXD to consume!

  VG  #PV #LV #SN Attr   VSize VFree
  ALL   4   0   0 wz--n- 7.27t 7.27t

Lets get up to date LXD:

apt update && apt upgrade -y
snap remove lxd
snap install lxd --channel=latest/stable

lxd init
Would you like to use LXD clustering? (yes/no) [default=no]: 
Do you want to configure a new storage pool? (yes/no) [default=yes]: 
Name of the new storage pool [default=default]: 
Name of the storage backend to use (dir, lvm, zfs, ceph, btrfs) [default=zfs]: lvm
Create a new LVM pool? (yes/no) [default=yes]: no
Name of the existing LVM pool or dataset: ALL
Would you like to connect to a MAAS server? (yes/no) [default=no]: no
Would you like to create a new local network bridge? (yes/no) [default=yes]: 
What should the new bridge be called? [default=lxdbr0]: 
What IPv4 address should be used? (CIDR subnet notation, “auto” or “none”) [default=auto]: 
What IPv6 address should be used? (CIDR subnet notation, “auto” or “none”) [default=auto]: 
Would you like the LXD server to be available over the network? (yes/no) [default=no]: 
Would you like stale cached images to be updated automatically? (yes/no) [default=yes]: 
Would you like a YAML "lxd init" preseed to be printed? (yes/no) [default=no]:

Show the result:

lxc storage list
| default | lvm    | ALL    |             | 1       | CREATED |

Lets have a look at the LXD storage pool created, as I’ve never seen an lvm pool before:

lxc storage show default
  lvm.thinpool_name: LXDThinPool
  lvm.vg_name: ALL
  source: ALL
  volatile.initial_source: ALL
description: ""
name: default
driver: lvm
- /1.0/profiles/default
status: Created
- none

Check that its not mounted and not using a loop device:

df -h
Filesystem      Size  Used Avail Use% Mounted on
udev             32G     0   32G   0% /dev
tmpfs           6.3G  1.6M  6.3G   1% /run
/dev/sda2        29G  2.9G   25G  11% /
tmpfs            32G     0   32G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs            32G     0   32G   0% /sys/fs/cgroup
/dev/loop0       62M   62M     0 100% /snap/core20/1611
/dev/loop2       47M   47M     0 100% /snap/snapd/16292
/dev/sda1       511M  5.3M  506M   2% /boot/efi
tmpfs           6.3G     0  6.3G   0% /run/user/0
/dev/loop1      103M  103M     0 100% /snap/lxd/23270
tmpfs           1.0M     0  1.0M   0% /var/snap/lxd/common/ns

Use lvs to show the new LXD created LVM thinpool on the volume group ALL:

  LV          VG  Attr       LSize  Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  LXDThinPool ALL twi-a-tz-- <7.25t             0.00   10.42

Hope this helps new users with lvm storage.

For more info on LVM with LXD please see LVM - lvm - LXD documentation