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anurag7
November 20th, 2012, 07:21 AM
Hi all, I have a single boot system with Ubuntu 11.10 and i'm unable to boot into it due to error unknown filesystem : grub rescue at prompt.
I tried to repair grub with a live usb stick as per the steps i found on forums but could not proceed further. These are the outputs of some of the commands:

sudo fdisk -l

Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 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: 0x0007f28c

Device Boot Start End Blocks Id System
/dev/sda1 * 2048 972847103 486422528 83 Linux
/dev/sda2 972849150 976771071 1960961 5 Extended
/dev/sda5 972849152 976771071 1960960 82 Linux swap / Solaris

Disk /dev/sdb: 4004 MB, 4004511744 bytes
116 heads, 51 sectors/track, 1322 cylinders, total 7821312 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/sdb1 * 32 7821311 3910640 b W95 FAT32

sudo fdisk -l /dev/sda1

Disk /dev/sda1: 498.1 GB, 498096668672 bytes
255 heads, 63 sectors/track, 60556 cylinders, total 972845056 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

Disk /dev/sda1 doesn't contain a valid partition table

sudo mount /dev/sda1 /mnt
mount: you must specify the filesystem type

sudo mount -t ext4 /dev/sda1 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/sda1,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

dmesg|tail
[ 66.881963] wlan0: associated
[ 66.889048] ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
[ 77.024032] wlan0: no IPv6 routers present
[ 475.357268] EXT3-fs (sda1): error: can't find ext3 filesystem on dev sda1.
[ 475.366696] EXT2-fs (sda1): error: can't find an ext2 filesystem on dev sda1.
[ 475.373330] EXT4-fs (sda1): VFS: Can't find ext4 filesystem
[ 475.388623] FAT-fs (sda1): invalid media value (0x00)
[ 475.388629] FAT-fs (sda1): Can't find a valid FAT filesystem
[ 475.404278] SQUASHFS error: Can't find a SQUASHFS superblock on sda1
[ 481.117560] EXT4-fs (sda1): VFS: Can't find ext4 filesystem


I'm pretty much a newbie to linux. It looks like the partition /dev/sda1 has lost some header information relating to filesystem. Is there any way i can recover from here or if i attempt to reinstall ubuntu on same partition can my data be saved?

Moose
November 20th, 2012, 07:33 AM
Have you made/deleted/edited any partitions since you installed your os?

PowerBarry43
November 20th, 2012, 11:55 AM
Hi

You could try downloading a supergrub boot disk which would allow you to boot into your installed Ubuntu if it's intact. from there you could run a sudo update-grub which would probably fix.

Hope this helps

Barry