Monday, December 16, 2013

How to mount disk used by ReadyNAS

The following steps are useful if we want to salvage data stored in the drive in ReadyNAS.
I am not sure if the steps below are going to work on other ReadyNAS models, but it works on my ReadyNAS Duo (Sparc CPU).

Basically, what we need is a SATA-to-USB cable (can be bought on the Internet for couple of bucks).
NETGEAR ReadyNAS partitions the drive into 4 partitions.  In my case, it is detected as /dev/sdc:


[root@r3000 media]# fdisk -l /dev/sdc

Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 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
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               2     4096001     2048000   83  Linux
/dev/sdc2         4096002     4608001      256000   82  Linux swap / Solaris
/dev/sdc3         4608002  1953092233   974242116    5  Extended
/dev/sdc5         4608003  1953092233   974242115+  8e  Linux LVM
[root@r3000 media]# 


There are couple of issues if we try to mount the partitions directly:

  1. ReadyNAS uses non-standard ext3 block-size, which in my case is 16384 bytes (use command "lvsc" to check)
  2. The home directory is partitioned as LV group, so conventional mount command is not gonna work
Here's the steps:
  • Scan the usb for LVM volumes and identify in the output the volume group name that has your READYNAS volume (mine proved to be c):
# vgscan
[root@r3000 media]# vgscan
  Reading all physical volumes.  This may take a while...
  Found volume group "c" using metadata type lvm2
  Found volume group "vg_r3000" using metadata type lvm2
  Found volume group "VolGroup" using metadata type lvm2

  • Activate the group for ReadyNAS (in this case, the group name is "C")
# vgchange -ay c
  • Find the logical volume that  (mine proved to be 'c'):
# lvs
  • root@r3000:/home/root# lvs
      LV   VG   Attr      LSize   Pool Origin Data%  Move Log Copy%  Convert
      c    c    -wi-ao--- 929.09g  
     
  • To display the logical name of the partition, use command "lvdisplay":
# lvdisplay /dev/c
  --- Logical volume ---
  LV Name                /dev/c/c
  VG Name                c
  LV UUID                7HUOrf-B5bL-ur6r-ULsd-yl4m-gCrA-zQc4s9
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                929.09 GiB
  Current LE             29731
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:5


We cannot use regular command "mount" to mount the non-standard blocksize ext3 partition.  Fortunately, there is a tool called "fuse-ext3" running in userspace that can help us.  The tool can be downloaded here.

Here's an example how to mount my ReadyNAS's LV volume:

fuse-ext2 -o sync_read,allow_other,rw+ /dev/c/c /media/readynas2

And here is the command to mount the system (root) partition which has the Linux software (I will post later about how to reset root password without resetting the ReadyNAS to factory default etc.)

fuse-ext2 -o sync_read,allow_other,rw+ /dev/c/c /media/readynas2




5 comments:

  1. Hello,

    Thanks for your job ! I successfully mount my partitions on Lubuntu LiveCD with this useful help.

    Regards

    ReplyDelete
  2. Hello,

    Thanks for your job ! I successfully mount my partitions on Lubuntu LiveCD with this useful help.

    Regards

    ReplyDelete
  3. My ReadyNAS Duo chassis died but the drives were still good. With this article I can attach the drive and copy my stuff to the new one. Thanks!

    ReplyDelete
  4. For completeness the command to unmount when you're done is

    fusermount -u /media/readynas2

    ReplyDelete