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I have a WD NAS drive, I need to recover some deleted files, so I've taken the drive out and plugged it into an Ubuntu machine to get direct access to the filesystem...

When I check the drive in parted I see:

Model: ATA WDC WD20EURS-63S (scsi)
Disk /dev/sdb: 2000GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt

Number  Start   End     Size    File system  Name     Flags
 3      15.7MB  528MB   513MB                primary
 1      528MB   2576MB  2048MB  ext3         primary  raid
 2      2576MB  4624MB  2048MB  ext3         primary  raid
 4      4624MB  2000GB  1996GB  ext4         primary

However, when I try mounting /dev/sdb4 with ext4...

root# mount -t ext4 /dev/sdb4 /media/2TB
mount: wrong fs type, bad option, bad superblock on /dev/sdb4,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

Any ideas why it wont mount?

Edit: When mounting without -t (for all partitions):

root# mount /dev/sdb /media/2TB
mount: you must specify the filesystem type
root# mount /dev/sdb1 /media/2TB
mount: unknown filesystem type 'linux_raid_member'
root# mount /dev/sdb2 /media/2TB
mount: unknown filesystem type 'linux_raid_member'
root# mount /dev/sdb3 /media/2TB
mount: you must specify the filesystem type
root# mount /dev/sdb4 /media/2TB
mount: wrong fs type, bad option, bad superblock on /dev/sdb4,
   missing codepage or helper program, or other error
   In some cases useful info is found in syslog - try
   dmesg | tail  or so
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The likelihood seems pretty low, but is it possible the kernel is missing ext4 support? – killermist Jun 13 '12 at 14:43
    
Looks like your NAS is using some sort of RAID, do you know what kind? Presumably its mirrored. – madmaze Jun 13 '12 at 14:43
    
There's only 1 drive in the NAS, so I really doubt there was any RAID going on... (it's a 2TB WD "MyBook Live" drive). – Ian Jun 13 '12 at 14:45
    
Also, mkfs.ext4 is available as a command, so I believe ext4 is there... – Ian Jun 13 '12 at 14:45
1  
Is it possible that the partition is false-flagged as ext4 when it is in fact something else, like ntfs (which is fairly common in NAS boxes)? – killermist Jun 13 '12 at 15:01

Check this guide. It’s worth to read the whole site, it’s very useful.

The command(s) you are searching for:

# if your filesystem is corrupted run this, then mkfs...    
mdadm --zero-superblock /dev/sdb1          

# creating /dev/md0    
mdadm --create /dev/md0 --raid-devices=2 --level=raid1 --run --metadata=0.90 /dev/sdb1 missing
  • assumed that your drive is /dev/sdb.
  • I recommend to read the guide before doing anything.
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I’m assuming you need the mdadm Linux software raid utility to deal with the partition #4 listed below from the WD Rescue procedure 2 web page. It is likely it is part of a software RAID array even if it is on a single disk. We see this on the Seagate NAS as well.

Your partition table should look like this:

  • Unallocated space. (This space is used to store individual system specific data, such as MAC address, serial number, etc.)
  • Partition #1, formatted as ext3. (This is the boot partition, with /boot, /root, etc. on it.)
  • Partition #2, formatted as swap (This is the system paging file.)
  • Partition #3, formatted as ext3 (This is the rest of the O/S, /var, etc.)
  • Partition #4, unknown format. (This is the data-store, don't modify or change this!)

The Partition #4 will likely need to be mounted as a RAID array. It is leaking the file system format of ext4 through but is probably still a RAID partition. Take a look at the above website for details on recovering a software raid partition.

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