Re: [Info-mtools] What does it take to support FAT12 dialects?

[Pali Rohár]

On Wednesday 19 May 2021 13:29:20 Alexander Huemer wrote:
> On Wed, May 19, 2021 at 05:32:36PM +0200, Pali Rohár wrote:
> > On Wednesday 19 May 2021 12:31:54 Alexander Huemer wrote:
> > > On Wed, May 19, 2021 at 05:10:13PM +0200, Pali Rohár wrote:
> > > > Hello! Is linux kernel able to mount image and access content of this
> > > > filesystem? Can you provide example of such image? I can look at it...
> > > 
> > > I have to admit that I didn't try before. Indeed, the kernel seems to be 
> > > able to mount a 1.2M image just fine! At least an `ls` shows content and 
> > > the md5sum of a known file is correct.
> > 
> > Ok, so my guess is that this 1.2M image is close-to-standard and if
> > mtools cannot read it, it could be some issue in mtools.
> > 
> > > A 2.4M image is being mounted, but `ls` shows garbage, and this is 
> > > ending up in the kernel ring buffer:
> > 
> > Just a question: Is this image clean and not corrupted? Because it does
> > not have valid information in FAT12/16 boot sector.
> 
> To the best of my knowledge the image is not corrupted. This image is 
> used to 'boot' the machine and was used for that successfully in several 
> situations.

Ok, thanks for confirmation! Then it would mean that this image is not
standard FAT12/16 and existing FAT12/16 tools would not be able to read
it.

So some kind of non-standard modification would be needed for reading
it.

Is there any public software which can generate filesystem in this
format?

> > > May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: 
> > > invalid start cluster (i_pos 0, start 0000abda)
> > > May 19 15:17:28 void kernel: FAT-fs (loop0): Filesystem has been set 
> > > read-only
> > > May 19 15:17:28 void kernel: FAT-fs (loop0): error, invalid access to FAT 
> > > (entry 0x00000a53)
> > > May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: 
> > > invalid start cluster (i_pos 0, start 00007007)
> > > May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: 
> > > invalid start cluster (i_pos 0, start 0000a389)
> > > May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: 
> > > invalid start cluster (i_pos 0, start 000070d1)
> > > May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: 
> > > invalid start cluster (i_pos 0, start 000070d1)
> > > May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: 
> > > invalid start cluster (i_pos 0, start 0000129f)
> > > May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: 
> > > invalid start cluster (i_pos 0, start 0000fdff)
> > > May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: 
> > > invalid start cluster (i_pos 0, start 000071d1)
> > > May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: 
> > > invalid start cluster (i_pos 0, start 000070d1)
> > > May 19 15:17:28 void kernel: FAT-fs (loop0): error, fat_get_cluster: 
> > > invalid start cluster (i_pos 0, start 0000129f)
> > > 
> > > I'll provide images off-list.
> > 
> > I have received them. I will try to look at it.
> 
> Thanks!
> 
> > > Thank you!
> > > 
> > > -Alex
> > > 
> > 
> > -- 
> > Pali Rohár
> > pali.rohar@gmail.com

-- 
Pali Rohár
pali.rohar@gmail.com