I installed Ubuntu 12.04 on my external USB drive, where I have a 700GB NTFS partition followed by the new 6GB ext4 partition and a swap partition (all primary). The GRUB MBR is also installed to the external hard disk.
Since my BIOS puts the external drive as first disk when booting, I removed my internal hard disk before installation in order to avoid ordering problems.
Now when I boot from the external drive, GRUB is stuck at the rescue console with the error "unknown filesystem".
grub rescue> ls
(hd0) (hd0,msdos3) (hd0,msdos2) (hd0,msdos1)
ls (hd0,<any of them>)/ gives me "unknown filesystem", thus also "insmod normal"
GRUB doesn't seem to be able to read my Linux partition as you can see above?! How can I solve this?
Additional info:
bootinfoscript says (this is with the internal drive in again, but that does not make a difference):
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.
sdb1: __________________________________________________________________________
File system: ntfs
Boot sector type: Windows Vista/7: NTFS
Boot sector info: No errors found in the Boot Parameter Block.
Operating System:
Boot files:
sdb2: __________________________________________________________________________
File system: ext4
Boot sector type: -
Boot sector info:
Operating System: Ubuntu 12.04 LTS
Boot files: /boot/grub/grub.cfg /etc/fstab /boot/grub/core.img
sdb3: __________________________________________________________________________
File system: swap
Boot sector type: -
Boot sector info:
Best Answer
I also experienced that issue. But I've found a workaround for this.
My USB drive has first NTFS partition of 430GB (sdg1) followed by Linux partition of 10 GB (sdg2) (all primary). I installed Ubuntu (or afterwards Trisquel) to it and had the same error about unknown filesystem.
It was that grub was unable to "see" Linux partition after such "large" NTFS partition. I don't know the exact limitations of GRUB2, but my 430GB was above it.
Here is the workaround:
Install grub to USB HDD with root directory at /dev/sdg1 (NTFS partition). You then will have grub.cfg in /boot/grub/ on that partition.
Copy kernel and inirtd image to /boot/ubuntu/ at /dev/sdg1.
Change grub.cfg to have root at 'hd0,msdos1' and to load kernel and initrd from /boot/ubuntu/.
Done.
Here is my grub.cfg entry, for example:
PS: this workaround won't work with every distro (with ArchBang, for example).