FAT12 format does not honor the -R option

FAT12 format does not honor the -R option

[Michael T. Kloos]

"mkfs.vfat -F 12 -R 2 /dev/loop0" does not seem to honor the -R option.  
It just defaults to 0x20 for the reserved sector count. I can hexedit 
the FS to move the file allocation table contents and change 0x20 to 
0x02 in the reserved sector count field. Mounting this seems to work 
fine under the Linux FAT driver from my limited experimentation.  It 
just seems like a waste of space reserving that many sectors in a FAT12 
FS where it is most likely to be used in space constrained 
applications.  Is this a bug or is it working around some compatibility 
issue with 2 reserved pages?


Thanks,
----Michael

Re: FAT12 format does not honor the -R option

[Karel Zak]

On Fri, Jan 15, 2021 at 11:01:45AM -0500, Michael T. Kloos wrote:
> "mkfs.vfat -F 12 -R 2 /dev/loop0" does not seem to honor the -R option. 

For mkfs.vfat see https://github.com/dosfstools/dosfstools. It's not
maintained by util-linux project.

 Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

Re: FAT12 format does not honor the -R option

[Michael T. Kloos]

If anyone is curious, I found the answer.  Per this thread:

https://github.com/dosfstools/dosfstools/issues/67

You have to use the -a option to disable alignment.  There is discussion 
in the thread of the addition of a warning to indicate to the user of 
this unexpected behavior and how to resolve it.

On 1/15/21 11:28 AM, Karel Zak wrote:
> On Fri, Jan 15, 2021 at 11:01:45AM -0500, Michael T. Kloos wrote:
>> "mkfs.vfat -F 12 -R 2 /dev/loop0" does not seem to honor the -R option.
> For mkfs.vfat see https://github.com/dosfstools/dosfstools. It's not
> maintained by util-linux project.
>
>   Karel
>