bugGNU GRUB - Bugs: bug #27069, Unknown filesystem error with...

 
 

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bug #27069: Unknown filesystem error with non-first partition of disk

Submitter:  Shaun Reich <sreich>
Submitted:  Tue 21 Jul 2009 06:40:50 PM UTC
   
 
Category:  Filesystem Severity:  Major
Priority:  5 - Normal Item Group:  Software Error
Status:  Invalid Privacy:  Public
Assigned to:  None Originator Name: 
Open/Closed:  Closed Release:  Bazaar - trunk
Release:  SVN Reproducibility:  Every Time
Planned Release:  None

Sat 17 Apr 2010 05:05:58 PM UTC, comment #2: 

This is a BIOS having 128GiB limitation. When USB subsystem in GRUB matures it will have a way to workaround it. But since USB-related tasks are already on task tracker and this bug is actually a BIOS bug I close this bug.

Vladimir Serbinenko <phcoder>
Group administrator
Thu 14 Jan 2010 02:27:28 AM UTC, comment #1: 

I ran into a similar problem recently. I think I know what's going on.

I installed (Ubuntu) Linux onto the end of a 500GB USB external hard drive, connected to a laptop. When I rebooted after the install, I got the "unknown filesystem" error. But if I then connected the same hard drive to a desktop machine I had, the Linux system booted correctly.

The problem, I believe, is just a plain old BIOS barrier limitation---it can't boot off the drive if the necessary /boot files are farther than a certain amount (137GB?) from the first sector. BIOS barriers may seem like a historical concern (137GB was an issue way back in 2001), but this came up on a fairly recent-model laptop, new enough to have a Core 2 Duo processor. It's plausible that BIOS code to boot off USB drives sometimes doesn't receive the same amount of attention as code to boot off standard IDE/SATA drives.

Of course, the reason why I wanted to install Linux at the tail end of the drive in the first place was so that the first partition would be a ~440GB FAT32 filesystem. And the reason for that is because, when the USB drive is plugged into a Windows system, Windows will only take notice of the first partition---and I wanted the drive to be useful as a data vehicle on non-Linux systems. (I'm not sure how MacOS X handles things, but I wouldn't be surprised if it did the same thing.)

The solution I eventually found online pointed out that Windows only cares about the first partition---i.e. partition number 1 in the drive's partition table (*)---but that partition does not also have to be the first one in the drive's actual physical layout. That is to say, I created a partition table (using fdisk(8)) that has the partitions out of order. The big FAT32 partition goes right up to the end of the disk, yet the system lists it as /dev/sdx1. Windows picks it up exactly as desired, and Linux boots happily, BIOS barrier or no.

(*) Alternately, this could be read as "the lowest-numbered partition in the partition table," but that is not something I took the time to confirm.

With all that said, I think this can be categorized not as a bug in GRUB2, but nonetheless as an operating hazard that the program could probably deal with in a better way---even if it's just printing a warning at an appropriate point in time.

Daniel Richard G. <iskunk>
Tue 21 Jul 2009 06:40:50 PM UTC, original submission:  

Hello,

I have been fiddling with the GRUB2 for a while now, thinking they were mostly problems with what I was doing...I have covered many bases, however.

First of all, I have been formatting my drives and converting them to Ext4..my 250 GB External(USB) was what I started with. I wanted to create an install of Linux on this, so as to serve as an up-to-date sort of LiveCD, thusly -- I wanted GRUB2 on it, so it can boot by itself.

So I created a new partition table on it, then created Partition #1 (235) GB then created Partition #2 (15 GB).

Both are Ext4, and the first is completely blank (I didn't add a thing to it), the second is where that Linux install is located, I installed Linux on it without installing GRUB at all...

I then booted into my normal install and installed GRUB2 onto it(first by chrooting into it, according to the link to the wiki via the IRC channel). After restarting, and selecting (via BIOS), to boot to that External drive, it came up with an error saying "GRUB Rescue \n Unknown Filesystem".

I even unplugged my other hard disks to be fully certain that it was not a different hard disk.

I then installed GRUB2 from SVN, hoping that it would resolve my problems and I installed it to the correct drive(even wiping the /boot/grub before hand), same error.

Well, I was experimenting with the rescue mode -- excellent work on this by the way, I'm glad I can try and debug the problem instead of it just saying there was some error in Stage 1 , etc...

So I typed 'ls' at the rescue prompt.

This listed my drives and their partitions, I only had 1 drive connected at that moment, so it would only find the External..

I typed 'set' and prefix=(hd0,2)/boot/grub and root=(hd0,2)

Well this looked fine, as the second partition is the only one that matters..so I tried to dig further...

I tried 'ls (hd0,2)/', but it comes up with the same error I have been getting...

I then tried 'ls (hd0,1)/' and listed was 'lost+found" (the ext-created folder). Well this means it had no problem listing the first partition... I even put some files on that partition and it read them fine.. I did not try putting GRUB2 on this first partition, as I would really rather not (I'm anal like that and like to have what I use the most categorized).

Also tried, was re-creating the partition table and remaking the partitions...I also tried recreating the second partition as ext3...same problem.

I think that's everything..let me know if you need more info, as I really *really* want this fixed quickly as I want to convert everything to ext4, get stuff setup, and get back to coding...

Thanks.

Shaun Reich <sreich>

 

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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2010-04-17 phcoder StatusNone Invalid
        Open/ClosedOpen Closed
        ReleaseNone Bazaar - trunk

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