Problem: continually getting "grub rescue" with "unknown filesystem" at boot. Attempted update-grub (see below) and boot-repair (see below) to no avail.

History: I am attempting a transfer of the contents from a small drive with dual-boot to a larger drive. The original drive was composed of 3 primary partitions:

sda1 windows XP
sda2 ubuntu 14.04.5
sda3 swap

My objective was to increase the windows partition size, and the ubuntu partition size. Doing this required moving the ubuntu partition.

Operations So Far: I dd'd directly from my old drive sda to the new drive sdb, shutdown, detached the original drive from the system leaving the new drive attached, rebooted to Live CD. The new drive is now sda. Using Live CD Gpartd, I first ONLY moved the swap partition sda3 to the end of the drive. I rebooted and verified that both Windows and Ubuntu booted successfully.

At this point, my drive looks like this:

sda1 windows
sda2 ubuntu
unallocated space
sda3 swap

Next, with Live CD Gpartd, I moved the ubuntu partition (sda2) to the right and increased its size (it retained its UUID).

sda1 windows
unallocated space
sda2 ubuntu
sda3 swap

In this state Ubuntu isnt bootable, but I tried anyway and got "grub rescue" with "unknown filesystem". Then I booted Live CD and performed the following:

sudo mount /dev/sda2 /mnt
sudo mount --bind /dev /mnt/dev
sudo mount --bind /sys /mnt/sys
sudo mount --bind /proc /mnt/proc
sudo chroot /mnt
<< verified /boot/grub contained grub.cfg, grubenv >>
sudo update-grub
<< completed successfully >>
sudo umount /mnt/dev
sudo umount /mnt/sys
sudo umount /mnt/proc
sudo umount /mnt/
<< reboot >>

Got "grub rescue" with "unknown filesystem". An "ls" showed expected partitions, but querying each returned "unknown filesystem".

I attempted boot-repair and my results are at: http://paste.ubuntu.com/24087678/

I also tried stepping over the newly moved and resized ubuntu partition with a clean ubuntu install on top of the ubuntu partition. As part of the install, I reformatted sda2 to ext4, kept the same swap partition. This also failed and booting returned "grub rescue" with "unknown filesystem".

When booting from Live CD or from my old drive, and inspecting the new drive, both the windows partition and ubuntu partition have coherent file systems and all files are present and readable.

I'm not using UEFI.

** Update ** Then I tried re-installing XP to sda1 in order to get the Windows bootloader. XP boot was successful. Then I dd'd my old sda1 to the new drive's sda1. Again XP boot was successful. I used GParted from a Live CD to increase sda1 by the adjacent unallocated space. XP boot was successful. Now my new drive layout is as desired but Ubuntu not bootable yet:

sda1 windows XP
sda2 ubuntu 14.04.5  << not bootable -- only have XP bootloader >>
sda3 swap

I installed Ubuntu 16.04.2 to sda2 and expected to get the dual-boot menu but again FAIL!!! Instead I get "grub rescue" with "unknown filesystem". In grub rescue, "ls" shows all expected partitions (including 2 other IDE drives I have attached).

(hd0) (hd0,msdos3) (hd0,msdos2) (hd0,msdos1)
(hd1) (hd1,msdos2) (hd1,msdos1)
(hd2) (hd2,msdos1)

When I "ls" each one, it reports "Filesystem is unknown".

Thanks for the help.

  • I see XP. How old is system? Are drives set for IDE or AHCI, should be AHCI. Some old BIOS with only IDE could not boot a file on a drive beyond 137GB. IDE mode may emulate that error. Old work around was either smaller / (root) inside first 100MB with separate /home or data partition(s), or separate /boot fully inside first part of drive. Windows may need drivers if you want to keep XP. I had to retire my XP as new SSD only worked with AHCI and XP only with IDE. – oldfred Mar 2 '17 at 1:16
  • It's an AHCI XP installation (with the first partition offset by 1,048,576 to achieve the proper SSD alignment). The boot drive is AHCI, and there are 2 other IDE drives which are not being modified. – Ken Conrad Mar 2 '17 at 7:24
  • May be best to see details, you can run from Ubuntu live installer or any working install: Post the link to the Create BootInfo summary report. Is part of Boot-Repair: help.ubuntu.com/community/Boot-Info and: sourceforge.net/p/boot-repair/home/Home With Multiple drives do not use Boot-Repair's auto fix. That installs one grub to all drives. You may want advanced mode, and choose an install and its drive manually. – oldfred Mar 2 '17 at 14:35
  • My boot info: Boot Info This was captured after another failed attempt to freshly install 16.04 to sda2 after changing UUIDs for ubuntu and swap partitions, sda2,sda3 -- got black screen boot repair. – Ken Conrad Mar 9 '17 at 17:14
  • I still wonder if your old BIOS only boots from files located in the first 137GB of drive? Many old systems had that issue, when newer larger hard drives were added to them. Some even booted, but then on update, new kernel or other boot file was beyond the 137GB limit. Your boot file are at 211GB on drive. See line 486 in report. – oldfred Mar 9 '17 at 18:08

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Browse other questions tagged or ask your own question.