How to fix "error: unknown filesystem. grub rescue>

Question

I'm not exactly sure what I did. I believe I installed ubuntu over windows on my acer netbook. I then tried to install linux mint, but it wouldn't start installing.

I turned the netbook off and back on. Now I get the error.

I have read alot of other questions like this but in my case I cannot boot a CD. If I put a ubuntu CD or a linux mint CD into my external cd/dvd drive and change my BIOS to boot the CD-ROM first, it just gives me the same error screen.

Update copied from comment dated 2012-05-26 02:54:29Z

Here are some results from my commands:

grub rescue>ls (hd0) (hd0,msdos5) (hd0,msdos1) 
grub rescue>ls (hd0,msdos5) unknown filesystem 
grub rescue>ls (hd0,msdos1) unknown filesystem 
grub rescue>ls (hd0) unknown filesystem 

Answer 1

Boot your system from the Ubuntu Live CD and try this, it worked wonders for me.

• Ubuntu Boot Repair Utility

Answer 2

first to boot into Ubuntu from iso.

1.Locate the Ubuntu partition and the folder containing the Grub modules.

The Grub folder containing the modules must be located so the correct modules can be loaded. This folder would have been created during the initial installation of Ubuntu and should be located in the Ubuntu partition. This folder would normally be located at either (hdX,Y)/boot/grub or (hdX,Y)/usr/lib/grub/i386-pc Find your existing Ubuntu partition and the module folder.

ls                               # List the known drives (hdX) and partitions (hdX,Y)
ls (hdX,Y)/                      # List the contents of the partition's root
ls (hdX,Y)/boot/grub             # Normal location of the Grub 2 modules.
ls (hdX,Y)/usr/lib/grub/i386-pc  # Alternate location of the Grub 2 modules.

• ls - should return all known drives (hdX) and partitions (hdX,Y)
• ls (hdX,Y)/ - should show the contents of the root directory of the partition.
• If you get an "error: unknown filesystem" this is not your Ubuntu partition.
• If this is the Ubuntu partition, you will see the Ubuntu folders, including lost+found/, home/, boot/ and vmlinuz and initrd.img. Use this address as the first part of the next command.
• ls (hdX,Y)/boot/grub - should display several dozen *.mod files. This is the folder you are looking for.
• If you don't find the modules, try the alternate location: ls (hdX,Y)/usr/lib/grub/i386-pc

2.Load the modules.

set prefix=(hdX,Y)/<path to modules>

• This command must correctly point to the folder containing the Grub modules. The address should be the one in the previous section which displayed the modules.

Examples:

set prefix=(hd0,5)/boot/grub 
set prefix=(hd1,1)/usr/lib/grub/i386-pc

• Load modules:

  insmod linux insmod loopback insmod iso9660 insmod fat # If ISO is located on fat16 or fat32 formatted partition. insmod ntfs # If ISO is located on an NTFS formatted partition. insmod nftscomp # If NTFS compression is used on the partition. Load if you aren't sure.

• A "file not found" error means that the path in the prefix is incorrect or the specific module does not exist. The prefix setting may be reviewed with the set command. Rerun the "set prefix=" command with the proper path.

3.Locate the Ubuntu ISO file.

• Using the combinations of ls commands, locate the Ubuntu ISO image.

4.Create the loopback device. loopback loop (hdX,Y)/<path to ISO>/<ISO-name.iso>

• Example:

  loopback loop (hd1,1)/path/to/ubuntu-10.04.1-desktop-i386.iso

5.Load the Linux kernel and initrd image.

set root=(loop)

linux /casper/vmlinuz boot=casper iso-scan/filename=/<ISO-name.iso> noprompt noeject

initrd /casper/initrd.lz

• If the path to the ISO or filename is not correct, the boot will halt at the BusyBox screen and produce a message stating "can't open /dev/sr0: No medium found".
• Note: If the ISO file is not in the / folder, include the path in the iso-scan/filename= entry. See second example.

• Examples:

  linux /casper/vmlinuz boot=casper iso-scan/filename=/ubuntu-10.04.1-desktop-i386.iso

  linux /casper/vmlinuz boot=casper iso-scan/filename=/my-iso/ubuntu-10.04.1-desktop-i386.iso

6.Boot.

• That should be it. If the commands ran without any messages/errors, the commands were accepted as entered. It's now time to boot:

  boot

further info here

Now do this after booting ::

here is post with same problem and is solved as below,

1.sudo mount /dev/sdaX /mnt

here sdaX is your boot partition. you can get list with sudo blkid like this,

/dev/sda1: LABEL="Windows XP" UUID="96A4390DA438F0FB" TYPE="ntfs" 
/dev/sda3: LABEL="Ubuntu 11.04" UUID="b61fcae3-7744-45b4-95b9-7528d50a3652" TYPE="ext4" 
/dev/sda5: LABEL="Se7en" UUID="A2DC9D71DC9D4109" TYPE="ntfs" 
/dev/sda6: LABEL="Development" UUID="DEB455A1B4557CC9" TYPE="ntfs" 
/dev/sda7: LABEL="EXTRA" UUID="D8A04109A040F014" TYPE="ntfs" 
/dev/sda8: LABEL="SONG" UUID="46080FCD080FBAC7" TYPE="ntfs" 
/dev/sda9: LABEL="BACKUPS" UUID="766E-BC99" TYPE="vfat" 

note: sdaX must be linux partition.

2.sudo grub-install --boot-directory=/mnt/boot /dev/sda

3.sudo update-grub

Answer 3

I got those steps working fine.

1. set root=(hd0,1)
2. set prefix=(hd0,1)/boot/grub
3. insmod normal
4. normal

The system works fine, but after the update-grub and grub-install doesn't work? Any idea?

This is a Ubuntu server 12.04 (Precise) installation, with a 2 disk raid.

Answer 4

These steps solved the issue. I am having Windows 7 & Ubuntu 10.04. After running steps on the below I don't need to run these every time and able to boot OSs normally:

1. set root=(hd0,6)
2. set prefix=(hd0,6)/boot/grub
3. insmod normal
4. normal
5. sudo update-grub (Run this in terminal after getting into Ubuntu)
6. sudo grub-install /dev/sda (Run this in terminal after getting into Ubuntu)

Answer 5

Your external CD/DVD is probably a USB device. You probably cannot tell BIOS to boot from it. When you start the ACER wacth for a message at the bottom (or top) of the screen saying something like "F2 to enter Setup, F12 for a Boot Menu". When you know what you need to press for the Boot Menu, put the CD in your external device, turn on or reboot the machine and slowly mash that key until you get a temporary menu allowing you to boot from the external CD.

You may need to use gparted from the CD to examine your hard drive and decide what to do to fix it so you can use it. That's beyond what I can describe here