Can't find my data on a btrfs partition

[branrjab29]

I recently installed openSUSE Leap 15.4 and it created a VFAT partition for boot, btrfs partition for my data and a swap partition. The directory /home has all my data as expected.

The /etc/fstab entry for /home looks like this:

LABEL=M15-HOME /home btrfs subvol=/@/home 0 0

If I take this drive and mount it on another machine as a USB drive, I have all the partitions but /home is empty.

I searched the entire btrfs partition and did not find my data.

Am I missing something about how to mount the btrfs partition?

 

[dos2unix]

Most of the systems I have that use BRTFS the partitions look like this..

UUID=e71e7fa7-3265-49b7-a08c-1937f60011d3 / btrfs subvol=root,compress=zstd:1 0 0
UUID=4176d238-9934-4ec8-aaca-10e75fa331cf /boot ext4 defaults 1 2
UUID=F6DE-831B /boot/efi vfat umask=0077,shortname=winnt 0 2
UUID=e71e7fa7-3265-49b7-a08c-1937f60011d3 /home btrfs subvol=home,compress=zstd:1 0 0
UUID=e71e7fa7-3265-49b7-a08c-1937f60011d3 /space btrfs subvol=space,compress=zstd:1 0 0
UUID=e71e7fa7-3265-49b7-a08c-1937f60011d3 /var btrfs subvol=var,compress=zstd:1 0 0
UUID=be87c305-a73b-425f-b60a-87f8abfa2a67 none swap defaults 0 0

It seems odd that it would mount based on a label, two different drives could have the same label, how would it know which is which? You can have a label, but the label shouldn't be the mount identifier.

Useful Mount Options of the Btrfs Filesystem

Like any other filesystems, the Btrfs filesystem also has a lot of mount options that you can use to configure the Btrfs filesystem's behavior while mounting the filesystem. How to mount a Btrfs filesystem with your desired mount options are explained in this article.

linuxhint.com

Note that all the BRTFS paritions have the same UUID. It's really just one partition.
We can test that with fdisk...

Disk /dev/nvme0n1: 1.86 TiB, 2048408248320 bytes, 4000797360 sectors
Disk model: INTEL SSDPEKNW020T8
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 2D8D43A1-51FD-44AA-8079-D5065F6995DB

Device Start End Sectors Size Type
/dev/nvme0n1p1 2048 456703 454656 222M EFI System
/dev/nvme0n1p2 456704 6748159 6291456 3G Linux filesystem
/dev/nvme0n1p3 6748160 31913983 25165824 12G Linux swap
/dev/nvme0n1p4 31913984 4000796671 3968882688 1.8T Linux filesystem

Yes, it's the same. I see my /boot/efi, and my /boot, and my swap. Everything else is one partition.

In reality, BTRFS volumes are like subvolumes. So you have to mount them like this.

Upgrading btrfs @home mount with dedicated drive

Hi, I currently have a single disk containing @ (root) and @home subvolumes. I’m using timeshift to take backups of the root partition and snapper (btrfs-assistant) to take backups of /home. Everything is working great except my disk is getting maxed out and so I want to migrate /home to a...

discussion.fedoraproject.org

 

[branrjab29]

Thanks for the responses. I didn't add a LABEL to the btrfs partitions, Leap 15.4 installation did. I think this does tell me what's going on. I didn't keep notes on everything I tried but I think that when I first plugged in the disk, there was a mount problem. I used a mount command to try to mount the partition so I wouldn't think a LABEL could be a problem, but I did get an error about not being able to mount and after some searching found a proposed solution using something like
btrfstune -u /dev/sda1
I think I got a message about it changing the UUID which seems like a bad thing. From there, the disk became unusable.

 

[dos2unix]

Having a label isn't a problem, using it as a mount identifier could be.

Mounting a BTRFS Subvolume

Porque Podemos Let's say there's a BTRFS filesystem happily running things in one location and it becomes desirable to use the same BTRFS filesystem in a different location. Traditionally would require the administrator to create a new partition or logical volume, format it, and mount it in...

www.cloudnull.io

 

[Tolkem]

Maybe you need to read here:

SDB:BTRFS - openSUSE Wiki

en.opensuse.org