Btrfs storage How do I add or remove devices?

LXD
1

As installing docker in containers using zfs is problematic I thought I’d create a btrfs storage.
That all works fine however if I want to add or remove a device from btrfs how do that within the LXD storage context?.

The issue is that created my btrfs storage from a single partition…
#lxc storage create btrfs btrfs source=/dev/ubuntu-vg/lxd-btrfs-0-lv

I’ve created a second btrfs partition and I’ld like to add it to the first…

From a CLI point of view I’d expect todo…
btrfs device add /dev/mapper/ubuntu–vg-lxd–btrfs–1–lv /mnt

But of course I’ve not for this partition mounted… So how do I tell lxd to use both for this storage?

Thanks in advance

2

You can actually do that with btrfs just fine but you’ll need to first mount it somewhere you can see it.

Try:

  • mount /dev/ubuntu-vg/lxd-btrfs-0-lv /mnt
  • btrfs device add /dev/ubuntu-vg-lxd-btrfs-1-lv /mnt
  • umount /mnt
1 Like
3

Thanks for that… Do you think it does any harm to leave it mounted?

4

Nope, the kernel treats additional mounts of a given block device as effectively bind-mounts, so no harm in keeping those around.

5

Brilliant thanks… I’ll add a mount into my next update…

6

Hello,

Can you also help me if i created a btrfs using block device and i want to add a new device?
Thanks in advance.

7

Here’s a how-to on adding/removing devices to/from a Btrfs filesystem from the official Btrfs wiki.