View Full Version : [ubuntu] Unknown Filesystem : Grub Rescue > on boot

January 1st, 2014, 03:02 PM
Hi Guys,

Booted to my laptop today to find the boot fail with the following prompt :
Unknown filesystem :
GRUB rescue >

My system is dual boot Win7 and Ubuntu 12.10 (?) and has been for quite some time. I'm not sure what has bought on the error, an update in either Win or Ubuntu ? Anyhoo...

Some Googling pointed me to the Boot-Repair-disk which I have burnt and run using the 'Fix Most Common Problems' button and also 'Advanced' with fix filesystem errors selected.
Both fixes failed with the laptop still booting to the above prompt.

Dump of Boot-Repair log is at

Any and all help appreciated

January 2nd, 2014, 02:24 AM
I've tried to boot manually from the rescue prompt without success using

set root=(hd0,5)
set prefix=(hd0,5)/boot/grub
insmod normal

which after a 5 second pause, again brings up 'Unknown filesystem'.

Should I have posted this in the 'Boot-Rescue' thread ?

As a last resort I've started to download the 13.10 iso :/

January 2nd, 2014, 05:47 AM
fdisk -l:

Disk /dev/sda: 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 / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x38d9e056

Device Boot Start End Blocks Id System
/dev/sda1 63 80324 40131 de Dell Utility
Partition 1 does not start on physical sector boundary.
/dev/sda2 * 81920 29044735 14481408 7 HPFS/NTFS/exFAT
/dev/sda3 29044736 418846719 194900992 7 HPFS/NTFS/exFAT
/dev/sda4 418848766 1953523711 767337473 5 Extended
Partition 4 does not start on physical sector boundary.
/dev/sda5 418848768 1941209087 761180160 83 Linux
/dev/sda6 1941211136 1953523711 6156288 82 Linux swap / Solaris

The numbers in 'blue' should be divisible by 8, or they should be multiples of 8 only.
You should adjust the above numbers to be multiples of 8. 'Fixparts (http://www.rodsbooks.com/fixparts/)' Utility will help you.
If it doesn't then you will have to change them manually, for windows partition USE any bootable 'Partition management' tool and for Linux use Gparted.
Run 'Boot-Repair' again and see if it helps.
NOTE: USE your 12.10 DVD to run 'Boot-Repair'. If the version of GRUB is not same on your 'repair disc' and 12.10 then there could be issues.

Also you have accumulated more than 20 unused kernels, you may want to clean up your system later.