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I know the question has been asked so many times but in my case whatever I do as indicated in the following post (all solutions are tried) 'unknown filesystem' is the ultimate reply..

Grub rescue - error: unknown filesystem

I also tried live USB of boot-disk-recovery which too fails to identify my device partition holding Ubuntu 12.04 x32 (which by the way is sdb2) Although it created bootscript which is attached below.

 Boot Info Script e7fc706 + Boot-Repair extra info      [Boot-Info 31Jan2013]


============================= Boot Info Summary: ===============================

 => Syslinux MBR (4.04 and higher) is installed in the MBR of /dev/sda.
 => Grub2 (v1.99) is installed in the MBR of /dev/sdb and looks at sector 1 of 
    the same hard drive for core.img. core.img is at this location and looks 
    for (,msdos2)/boot/grub on this drive.

sda1: __________________________________________________________________________

    File system:       vfat
    Boot sector type:  SYSLINUX 4.05 20120702
    Boot sector info:  Syslinux looks at sector 1030576 of /dev/sda1 for its 
                       second stage. SYSLINUX is installed in the  directory. 
                       According to the info in the boot sector, sda1 starts 
                       at sector 0. But according to the info from fdisk, 
                       sda1 starts at sector 62.
    Operating System:  
    Boot files:        /syslinux/syslinux.cfg /ldlinux.sys

sdb1: __________________________________________________________________________

    File system:       swap
    Boot sector type:  -
    Boot sector info: 

sdb2: __________________________________________________________________________

    File system:       
    Boot sector type:  -
    Boot sector info: 
    Mounting failed:   mount: unknown filesystem type ''

sdb3: __________________________________________________________________________

    File system:       Extended Partition
    Boot sector type:  Unknown
    Boot sector info: 

sdb5: __________________________________________________________________________

    File system:       
    Boot sector type:  Windows Vista: NTFS
    Boot sector info: 
    Mounting failed:   mount: unknown filesystem type ''
mount: unknown filesystem type ''

============================ Drive/Partition Info: =============================

Drive: sda _____________________________________________________________________

Disk /dev/sda: 4003 MB, 4003463168 bytes
124 heads, 62 sectors/track, 1017 cylinders, total 7819264 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes

Partition  Boot  Start Sector    End Sector  # of Sectors  Id System

/dev/sda1    *             62     7,818,695     7,818,634   c W95 FAT32 (LBA)


Drive: sdb _____________________________________________________________________

Disk /dev/sdb: 80.0 GB, 80026360832 bytes
255 heads, 63 sectors/track, 9729 cylinders, total 156301486 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes

Partition  Boot  Start Sector    End Sector  # of Sectors  Id System

/dev/sdb1               2,048     2,000,895     1,998,848  82 Linux swap / Solaris
/dev/sdb2    *      2,000,896    58,644,479    56,643,584  83 Linux
/dev/sdb3          58,646,526   156,301,311    97,654,786   5 Extended
/dev/sdb5          58,646,528   156,301,311    97,654,784   7 NTFS / exFAT / HPFS


"blkid" output: ________________________________________________________________

Device           UUID                                   TYPE       LABEL

/dev/loop0                                              squashfs   
/dev/sda1        3273-D2BD                              vfat       
/dev/sdb1        19d35932-1dbf-4be0-83aa-3d76b646dd80   swap       

================================ Mount points: =================================

Device           Mount_Point              Type       Options

/dev/loop0       /rofs                    squashfs   (ro,noatime)
/dev/sda1        /cdrom                   vfat       (ro,noatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)


========================= sda1/syslinux/syslinux.cfg: ==========================

--------------------------------------------------------------------------------
# D-I config version 2.0
include menu.cfg
default vesamenu.c32
prompt 0
timeout 300
ui gfxboot bootlogo
--------------------------------------------------------------------------------

================= sda1: Location of files loaded by Syslinux: ==================

           GiB - GB             File                                 Fragment(s)

            ?? = ??             syslinux/syslinux.cfg                          1
            ?? = ??             ldlinux.sys                                    1
            ?? = ??             syslinux/chain.c32                             1
            ?? = ??             syslinux/gfxboot.c32                           1
            ?? = ??             syslinux/vesamenu.c32                          1

============== sda1: Version of COM32(R) files used by Syslinux: ===============

 syslinux/chain.c32                 :  COM32R module (v4.xx)
 syslinux/gfxboot.c32               :  COM32R module (v4.xx)
 syslinux/vesamenu.c32              :  COM32R module (v4.xx)

======================== Unknown MBRs/Boot Sectors/etc: ========================

Unknown BootLoader on sdb3

00000000  d6 d6 d6 d6 d6 d6 d6 d6  d6 d6 d6 d6 d6 d6 d6 d6  |................|
*
000001b0  d6 d6 d6 d6 d6 d6 d6 d6  d6 d6 d6 d6 d6 d6 00 fe  |................|
000001c0  ff ff 07 fe ff ff 02 00  00 00 00 18 d2 05 00 00  |................|
000001d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa  |..............U.|
00000200


=============================== StdErr Messages: ===============================

File descriptor 8 (/proc/2401/mounts) leaked on lvscan invocation. Parent PID 7264: bash
  No volume groups found

ADDITIONAL INFORMATION :
=================== log of boot-repair 2013-11-26__17h13 ===================
boot-repair version : 3.198~ppa16~raring
boot-sav version : 3.198~ppa16~raring
glade2script version : 3.2.2~ppa45~raring
boot-sav-extra version : 3.198~ppa16~raring
File descriptor 8 (/proc/2401/mounts) leaked on lvs invocation. Parent PID 4002: /bin/sh
No volume groups found
boot-repair is executed in live-session (Boot-Repair-Disk 32bit 24avr2013, raring, Ubuntu, i686)
ls: cannot access /home/usr/.config: No such file or directory
CPU op-mode(s):        32-bit, 64-bit
noprompt cdrom-detect/try-usb=true file=/cdrom/preseed/lubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash --

=================== os-prober:


=================== blkid:
/dev/loop0: TYPE="squashfs"
/dev/sda1: UUID="3273-D2BD" TYPE="vfat"
/dev/sdb1: UUID="19d35932-1dbf-4be0-83aa-3d76b646dd80" TYPE="swap"

=================== UEFI/Legacy mode:
This live-session is not EFI-compatible.
SecureBoot maybe enabled.


=================== PARTITIONS & DISKS:



=================== parted -l:

Model: Kingston DT 101 G2 (scsi)
Disk /dev/sda: 4003MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type     File system  Flags
1      31.7kB  4003MB  4003MB  primary  fat32        boot, lba


Model:  Mass Storage Device (scsi)
Disk /dev/sdb: 80.0GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type      File system     Flags
1      1049kB  1024MB  1023MB  primary   linux-swap(v1)
2      1024MB  30.0GB  29.0GB  primary                   boot
3      30.0GB  80.0GB  50.0GB  extended
5      30.0GB  80.0GB  50.0GB  logical   ntfs

=================== parted -lm:

BYT;
/dev/sda:4003MB:scsi:512:512:msdos:Kingston DT 101 G2;
1:31.7kB:4003MB:4003MB:fat32::boot, lba;

BYT;
/dev/sdb:80.0GB:scsi:512:512:msdos: Mass Storage Device;
1:1049kB:1024MB:1023MB:linux-swap(v1)::;
2:1024MB:30.0GB:29.0GB:::boot;
3:30.0GB:80.0GB:50.0GB:::;
5:30.0GB:80.0GB:50.0GB:ntfs::;


=================== mount:
/cow on / type overlayfs (rw)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type devtmpfs (rw,mode=0755)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
/dev/sda1 on /cdrom type vfat (ro,noatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)
/dev/loop0 on /rofs type squashfs (ro,noatime)
none on /sys/fs/cgroup type tmpfs (rw)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev)
none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
none on /run/shm type tmpfs (rw,nosuid,nodev)
none on /run/user type tmpfs (rw,noexec,nosuid,nodev,size=104857600,mode=0755)
gvfsd-fuse on /run/user/lubuntu/gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,user=lubuntu)


=================== ls:
/sys/block/sda (filtered):  alignment_offset bdi capability dev device discard_alignment events events_async events_poll_msecs ext_range holders inflight power queue range removable ro sda1 size slaves stat subsystem trace uevent
/sys/block/sdb (filtered):  alignment_offset bdi capability dev device discard_alignment events events_async events_poll_msecs ext_range holders inflight power queue range removable ro sdb1 sdb2 sdb3 sdb5 size slaves stat subsystem trace uevent
/dev (filtered):  agpgart alarm ashmem autofs binder block bsg btrfs-control bus char console core cpu cpu_dma_latency disk dri ecryptfs fb0 fd full fuse fw0 hidraw0 hidraw1 hidraw2 hpet input kmsg kvm log mapper mcelog mem net network_latency network_throughput null oldmem port ppp psaux ptmx pts random rfkill rtc rtc0 sda sda1 sdb sdb1 sdb2 sdb3 sdb5 sg0 sg1 shm snapshot snd stderr stdin stdout uinput urandom usb v4l vga_arbiter vhost-net video0 zero
ls /dev/mapper:  control

=================== df -Th:

Filesystem     Type       Size  Used Avail Use% Mounted on
/cow           overlayfs  1.5G   19M  1.5G   2% /
udev           devtmpfs   1.5G   12K  1.5G   1% /dev
tmpfs          tmpfs      300M  816K  299M   1% /run
/dev/sda1      vfat       3.8G  496M  3.3G  14% /cdrom
/dev/loop0     squashfs   431M  431M     0 100% /rofs
none           tmpfs      4.0K     0  4.0K   0% /sys/fs/cgroup
tmpfs          tmpfs      1.5G  8.0K  1.5G   1% /tmp
none           tmpfs      5.0M     0  5.0M   0% /run/lock
none           tmpfs      1.5G     0  1.5G   0% /run/shm
none           tmpfs      100M   12K  100M   1% /run/user

=================== fdisk -l:

Disk /dev/sda: 4003 MB, 4003463168 bytes
124 heads, 62 sectors/track, 1017 cylinders, total 7819264 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: 0x00011134

Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *          62     7818695     3909317    c  W95 FAT32 (LBA)

Disk /dev/sdb: 80.0 GB, 80026360832 bytes
255 heads, 63 sectors/track, 9729 cylinders, total 156301486 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: 0x7add7add

Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     2000895      999424   82  Linux swap / Solaris
/dev/sdb2   *     2000896    58644479    28321792   83  Linux
/dev/sdb3        58646526   156301311    48827393    5  Extended
/dev/sdb5        58646528   156301311    48827392    7  HPFS/NTFS/exFAT


Error: no partitions

=================== Default settings
Recommended-Repair
This setting would reinstall the  of .
Additional repair would be performed:  repair-filesystems

=================== Settings chosen by the user
Boot-Info
This setting will not act on the MBR.



No change has been performed on your computer.

While I attach this sdb (as external) to any running OS following observations were made:

In Linux Mint's gPArted: Partitions /sdb1 (ext4) & /sdb5 (ntfs) both have exclamation marks! (thus my ntfs too is corrupted somehow)

In Win7 /sdb5 also can't be accessed rather windows offer me to format it to use it. chkdsk can't access this ntfs partition!

I have tested my hd for bad sectors but it's healthy & why it shouldn't be its only ~3 months old. Now I have tried whatever I can for the last 2 days but now you guys I look upon for assistance

UPDATE 1 I have tried fsck.ext4 -v /dev/sdb2 but bad superblock error was returned. Used mke2fs -n /dev/sdb2 to get a list of backup superblocks & finally upon each block number e2fsck -b <block_number> /dev/xxx was performed with no success :(

Source for above method

UPDATE 2 Used testdisk utility & performed deep search for lost partitions & then tried to list files upon each found partition some of the NTFS partiton allowed me to enter them but there were no files only "System Volume Information" stuff (some files I put in my /dev/sd5 should be there!). It displayed that hd structure is present but I can't hook up in the Linux partition nether testdisk was able to list files of that particular partition

UPDATE 3 This is the 3rd day & still I can't get it to work so I am writing a prologue of how did my problem really started...This 80gb drive though is my internal PC drive but frequently I also attach this as an external drive to my laptop. The drive was working fine for about 3 months.

Under linux Mint (in my laptop) I attached it 3 days before (& I often do that) as an external USB drive. There I transferred ~16gb of data to its NTFS partition /dev/sdb5. It went smoothly with ~25mb/sec rate & then I (what I do always) issued through context menu 'Safely remove drive' & it removed drive (I think that was what supposed to happen) nothing special! but later when I tried to boot it nightmare started...

After a quick Google search I must acknowledge that Linux may also corrupt your Grub & all even when drive isn't properly unmounted, thats really a shame to find because in windows I just pull out my USBs when transfer finishes but yes in *nix I do have found that even when transfer is completed & you pull out drive only to find nothing has been transferred! Bad luck if you used cut/paste

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1 Answer

Several problems:

  1. Windows really wants to be on a primary partition, not a logical partition in the extended partition, and that's the partition which should have the boot flag, not the linux partition, which does not care. * Oh its just for data, nevermind.
  2. Maybe you really don't have a filesystem on sdb2. Everything seems to indicate that. So just reinstall Ubuntu there (After fixing the Windows partition problem).

With no blkids being listed for the partitions, it does not look good for recovery. I suppose you could check the partition with dd, grab a few blocks at a time in locations spread across the partition, and look for strings, to see if the data even exists. But if it's just configuration data, definitely not worth the effort. For more valuable data, if the usual tools don't help, there's always brute force, dd the whole partition, split it up into manageable chunks, look for strings of interest, then edit the chunk with the interesting stuff -- a massive undertaking.

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There is no windows, there is just linux! /dev/sdb5 is just a logical NTFS storage drive! I know I can reinstall ubuntu but then why should I bother to question here. Are all my configurations are gone/unrecoverable? –  nightcrawler Nov 28 '13 at 14:02
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