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Problems accessing disks from a Synology NAS from a Linux PC

My Synology DS220+ died and I decided that the successor will be a DIY system. Now I'm trying to access the data from the disks that were used in the NAS.

Every tutorial, blog post, forum post I find about that topic boils down to this [KB article from Synology](https://kb.synology.com/en-global/DSM/tutorial/How_can_I_recover_data_from_my_DiskStation_using_a_PC), which doesn't work for me.

I tried this at first with Ubuntu 24.04, then, after finding a comment that the `mdadm` tools on Ubuntu 20.04 and newer are "too new" I tried it with 18.04, and even with 16.04 after someone proclaimed that 18.04 is too new as well. I get the same result in all cases.

Here is the result from my Ubuntu 18.04 VM:

```console
root@ubuntu:~# lsblk
NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0                        11:0    1 1024M  0 rom  
vda                       252:0    0   15G  0 disk 
├─vda1                    252:1    0    1M  0 part 
├─vda2                    252:2    0    1G  0 part /boot
└─vda3                    252:3    0   14G  0 part 
  └─ubuntu--vg-ubuntu--lv 253:0    0   14G  0 lvm  /
vdb                       252:16   0  1.7T  0 disk 
root@ubuntu:~# fdisk -l /dev/vdb
Disk /dev/vdb: 1.7 TiB, 1801763774464 bytes, 3519069872 sectors
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: dos
Disk identifier: 0x00000000

Device     Boot Start        End    Sectors Size Id Type
/dev/vdb1           1 4294967295 4294967295   2T ee GPT
```

Note: `vdb` is the disk in question, Ubuntu has its own logical volume. This is a 4TB WD disk, no idea why it is shown as a 1.7TB with a 2TB partition. This is consistent through all my tries.

```console
root@ubuntu:~# mdadm -AsfRv
mdadm: looking for devices for further assembly
mdadm: cannot open device /dev/sr0: No medium found
mdadm: no recogniseable superblock on /dev/dm-0
mdadm: Cannot assemble mbr metadata on /dev/vdb
mdadm: no recogniseable superblock on /dev/vda3
mdadm: no recogniseable superblock on /dev/vda2
mdadm: no recogniseable superblock on /dev/vda1
mdadm: Cannot assemble mbr metadata on /dev/vda
mdadm: No arrays found in config file or automatically
root@ubuntu:~# vgchange -ay
  1 logical volume(s) in volume group "ubuntu-vg" now active
root@ubuntu:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
unused devices: <none>
root@ubuntu:~# lvs
  LV        VG        Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  ubuntu-lv ubuntu-vg -wi-ao---- <14.00g            
```

The next step would be to mount either the logical volume, or the mdraid device, but I have neither, so I have to stop here.

I had two disk in the DS, both configured as a single volume, no RAID. One of the disks was holding important stuff, of which I have a backup. No loss here. The second disk was holding rather unimportant stuff, where the loss is rather a nuisance, hence no backup. I'd still like to rescue some stuff from it if possible.

I also tried to access the disk by installing Xpenology in a virtual machine, and adding the disk to it. It didn't recognize the disk at all though. I don't know how much of this issue is caused by the virtualization layer, I may try some of this again when the last of the hardware of the new NAS build finally arrives, until then VMs are my only means of trying this.[]()