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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, 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:
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.
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.
I don't know if it is relevant, but for the record, the last version running on my DiskStation was 7.3.1, it didn't come back after installing 7.3.1-86003 Update 1.
1 answer
The following users marked this post as Works for me:
| User | Comment | Date |
|---|---|---|
| GeraldS | (no comment) | Dec 2, 2025 at 12:59 |
As it turns out my problem was two-fold. One problem was my USB SATA adapter, after I got hands on a computer where I could attach the disks directly they showed up with the proper sizes and I got directly to the point where I could actually try to mount the disks.
root@ubuntu:~$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 5.5T 0 disk
├─sda1 8:1 0 2.4G 0 part
├─sda2 8:2 0 2G 0 part
└─sda5 8:5 0 5.5T 0 part
└─md2 9:2 0 5.5T 0 raid1
├─vg1-syno_vg_reserved_area 253:2 0 12M 0 lvm
└─vg1-volume_1 253:3 0 5.5T 0 lvm
sdb 8:16 0 2.7T 0 disk
├─sdb1 8:17 0 2.4G 0 part
├─sdb2 8:18 0 2G 0 part
└─sdb5 8:21 0 2.7T 0 part
└─md3 9:3 0 2.7T 0 raid1
├─vg2-syno_vg_reserved_area 253:0 0 12M 0 lvm
└─vg2-volume_2 253:1 0 2.7T 0 lvm
nvme0n1 259:0 0 465.8G 0 disk
├─nvme0n1p1 259:1 0 1M 0 part
└─nvme0n1p2 259:2 0 465.8G 0 part /
What also did not work at first was mounting the disks, I got errors from btrfs. But after some searching I found this post on Reddit, which solved this issue for me. It's not only the old Ubuntu that is necessary, you also need to install an older kernel than the one shipped latest with it, because a btrfs patch was included in later kernel builds that caused the mounting issue. I installed the package linux-image-4.15.0-108-generic, edited /etc/default/grub to set GRUB_TIMEOUT=5 and commented out GRUB_TIMEOUT_STYLE=hidden so I could select the correct kernel at boot and after that I could mount the Synology disks without problems.
So, to sum up the process to access the Synology disks from a PC:
- Attach the disks to a computer directly (not via USB adapter)
According to other posts on the mentioned Reddit thread this also works on a VM when you pass the disks through directly. I haven't tested this - Install Ubuntu 18.04
- Follow the Synology KB article with the addition of installing and booting into the correct kernel
sudo -i
nano /etc/default/grub
apt-get update
apt-get install -y mdadm lvm2 btrfs-progs linux-image-4.15.0-108-generic
reboot # select the correct kernel
mdadm -AsfR && vgchange -ay
cat /proc/mdstat
lvs
Mount the disks as needed.
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