Re: [Libguestfs] Root btrfs partition listed twice?
On Monday, April 28, 2014 10:02:54 AM Matthew Booth wrote:
>> For the record, here's the full filesystem list:
>>> <fs> list-filesystems
>>
>> /dev/sda1: swap
>> btrfsvol:/dev/sda2/@: btrfs
>> btrfsvol:/dev/sda2/boot/grub2/i386-pc: btrfs
[...]
>> btrfsvol:/dev/sda2/.snapshots: btrfs
>> /dev/sda2: btrfs
It looks like /dev/sda2 is both the root of the btrfs filesystem and a
subvolume called '@'. In Fedora, at least when I wrote this, subvolumes
where created underneath the btrfs root, so the btrfs root itself would
never be mistaken for the root filesystem.
Is '@' btrfs magic that means the root? If so, is it always listed? If
/dev/sda2 and btrfsvol:/dev/sda2/@ will always mean the same filesystem,
we should filter out the former if the latter exists. We need to nail
down exactly what '@' means first, though.
Thanks for the comments. It looks like @ is just a naming convention that we
have chosen for the root of the btrfs volume. I've seen the same thing in
Ubuntu (http://askubuntu.com/questions/331233/creating-btrfs-subvolume-like-or-home), and
I suppose it could be in other places as well. Here's the output
of `btrfs subvolume list /`:
ID 257 gen 85 top level 5 path @
ID 258 gen 85 top level 257 path boot/grub2/i386-pc
ID 259 gen 85 top level 257 path boot/grub2/x86_64-efi
[...]
ID 272 gen 85 top level 257 path var/tmp
ID 278 gen 85 top level 257 path .snapshots
and `btrfs subvolume show /`:
Name: @
uuid: 8add32ac-4abf-af49-bdeb-bfbf1ae5ecd8
Creation time: 2014-04-23 13:23:50
Object ID: 257
Generation (Gen): 105
Gen at creation: 7
Parent: 5
Top Level: 5
Flags: -
Snapshot(s): .snapshots/1/snapshot
As this is more than just a SUSE thing, it seems like filtering out the non-
btrfsvol device would be the right approach...
-Mike