1

Short story:

A disk with partitions sdb1-sdb4 and filetype ext4 now shows up as sdb with no file type. While trying to mount sdb I get the messages:

mount: /dev/sdb is write-protected, mounting read-only
mount: unknown filesystem type '(null)'

I believe that the power had gone out, but everything else on the server seems to be working fine. I had only mounted it using mount /dev/sdb4 /wdmycloud.

How do I go about accessing the partitions and data that should be on that drive?


Long Story

I have a 3 TB WD mycloud that could no longer be accessed by the network, so after tens of hours trying to make it work I pulled the drive out of its enclosure and plugged it into a USB dock on my CentOS 7, minimal install system.

The disk has several partitions. sdb1, sbd2, sbd3, sdb4, and maybe some others, but the one with my backed up information was sdb4.

I mounted it like so: mount /dev/sdb4 /wdmycloud and then copied my family pictures and videos off of it to my Windows machine via ftp, but left some documents and files to be recovered later as it was taking quite a long time.

Later I came back and the previously mounted folder wdmycloud was empty. I checked the disks with lsblk -f and it reads

NAME            FSTYPE      LABEL UUID                                   
MOUNTPOINT
sda
├─sda1          xfs               76a06aa5-7cc2-437b-837a-31d5b8f46d71   /boot
└─sda2          LVM2_member       YJTbNJ-IOnq-M8V9-l5HF-Yy5E-P2oS-YgD1Ct
  ├─centos-root   xfs               ff6b11a5-ca5e-4be9-a8c0-f31cee1af190   /
  ├─centos-swap   swap              dd47b390-c3e8-43d9-94c7-eff8d085fbf3 [SWAP]
  └─centos-home  xfs               7abd7360-bf08-4dd0-a08d-60df94281a4e   /home
sdb
sr0

I don't remember there being an sr0 device before, but it doesn't mean that it wasn't there. The partitions on sdb seem to be gone. While trying to mount sdb it I get the messages:

mount: /dev/sdb is write-protected, mounting read-only
mount: unknown filesystem type '(null)'

How do I go about accessing the partitions and data that should be on that drive?

Note: I've tried checking the integrity of the drive with fsck. It gives this error:

The superblock could not be read or does not describe a correct ext2 filesystem.

There are (or were) several partitions and the main one is ext4. The others I'm not sure about.

  • General note #1: A (physical) disk generally doesn’t have a filesystem type.  A physical disk typically has partitions (which can be thought of as logical disks).  Each partition can have a filesystem, and they can be all the same type, or a mixture of different types, including (null).  If a disk (e.g., sdb) has a filesystem, that means it doesn’t have partitions.  It is possible to use the entire disk for one filesystem, but it’s not a great idea. … (Cont’d) – G-Man Feb 7 '18 at 18:29
  • (Cont’d) …  General note #2: sr is a common name for an optical disc (CD/DVD) drive.  … … … … …  To get somewhat to the point, if you had a filesystem on sdb4, you should not be trying to mount or fsck sdb.  It looks like your partition table got corrupted, so the operating system can’t find the partitions.  Worst case scenario: the disk is totally erased or overwritten. … (Cont’d) – G-Man Feb 7 '18 at 18:29
  • (Cont’d) …  But it’s quite possible that the partitions, and all their data, are still there — just misplaced.  I’m not sure exactly how to handle this, but (1) look at our data-recovery questions, and see if you can find something that matches your problem.  And (2) research programs like fdisk and GParted, and see if you can figure out how to use them to recover your partition table.   Be very careful — if your data are still on the disk, an error at this point could wipe it out. – G-Man Feb 7 '18 at 18:29

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.