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Fibab

Member

Registered: 2024-05-08

Posts: 2

btrfs no subvol uuid

Hi,
I have migrated an old machine from ext4 to btrfs using btrs-convert, which works better than I expected using inplace conversion.
Now I wanted to use btrs send/receive via snap-sync for backups but it does not work as there is no UUID set in the subvolume.

btrfs subvol show /home   
/
	Name: 			<FS_TREE>
	UUID: 			-
	Parent UUID: 		-
	Received UUID: 		-
	Creation time: 		-
	Subvolume ID: 		5
	Generation: 		174257
	Gen at creation: 	0
	Parent ID: 		0
	Top level ID: 		0
	Flags: 			-
	Send transid: 		0
	Send time: 		-
	Receive transid: 	0
	Receive time: 		-
	Snapshot(s):
				.snapshots
				.snapshots/629/snapshot
				.snapshots/635/snapshot
				.snapshots/636/snapshot
				.snapshots/644/snapshot
				.snapshots/645/snapshot
				.snapshots/646/snapshot
				.snapshots/647/snapshot
	Quota group:		n/a

My other devices that I formatted directly as btrfs have a value for UUID. With btrfstune -u I can only set the filesystem uuid, which of course is already set. I couldn't find a way to set/modify the subvol uuid.

ua4000

Member

Registered: 2015-10-14

Posts: 558

Re: btrfs no subvol uuid

I have no solution, but maybe a workaround:
"Snapshot" your current home to a new one, e.g. like this

btrfs subvolume snapshot  /home /home2

Has /home2 an uuid ? If yes, make your home2 to your new home:

mv /home /home_old
mv /home2 /home

Fibab

Member

Registered: 2024-05-08

Posts: 2

Re: btrfs no subvol uuid

btrfs subvolume snapshot  /home /home2

gives me an

ERROR: cannot snapshot '/home': Invalid cross-device link

because my /home is an entire lvm partition of my disk. I know it's not the btrfs way to do this but the structure came from the previous ext4 setup which has been migrated by btrs-convert