Reformat an NTFS disk to FAT32?

[Bruce Labitt]

Ben Scott wrote:
> On Sun, Apr 20, 2008 at 11:11 AM, Bruce Labitt <bruce.labitt at verizon.net> wrote:
>   
>> I've looked around for this and I see a way or two to do this.
>>     
>
>   As usual, I'm going to ask: Why are you doing this?  What are you
> trying to accomplish?  :-)
>
>   
Now that I think about this, all that I want is a format that I can read 
and write to for the WinXP machines that I have to live with and with 
linux.  The disk does not need to be bootable from XP.  Unfortunately 
when I received the disk it already was preformatted NTFS.  I don't have 
any ntfs tools on my old distro.  (I want the disk so I can store  stuff 
so I can migrate to a home copy of Scientific Linux.)  I just want to 
have FAT32 on it so I can somewhat indiscriminately use the disk for 
both linux and windoze.
>>  One could use mkdosfs, but the documentation indicates that
>> the disk won't be bootable.
>>     
>
>   Any FAT filesystem created by mkdosfs won't be bootable, because all
> mkdosfs does is create a filesystem.  It doesn't install an operating
> system.
>
>   What OS are you looking to boot from the FAT partition?  Or are you?
>   
Nope - don't really need to.
>   Generally speaking, if you're looking to install a bootable OS, I
> recommend using the tools native to that OS to do so.
>
>   In the world of Microsoft, to install a bootable MS-DOS, you boot
> from floppy or CD.  You use FDISK to create the partition, then
> rebooted (still from floppy/CD) (DOS only checked the partition table
> at boot).  Then you ran "SYS C:" (where "C:" is the partition you just
> created).  That installed a boot loader and copied the DOS sustems
> files (IO.SYS and MSDOS.SYS) to the proper places, along with the
> shell (COMMAND.COM).
>
>   Windows NT and descendants generally require you to run the
> full-blown GUI "SETUP" routine.  The OS is too complicated; there's no
> trivial install possible.
>
>   Windows 3.x/95/98/ME load on top of DOS, and aren't really magic
> beyond that, but getting a working install going in the first place
> still needs the "SETUP" routine.
>
>   
>>  I think it should be possible in fdisk ...
>>     
>
>   fdisk only works with partitions, not filesystems.
>
>   You might want to use a more sophisticated tool, like qtparted or
> gparted or even parted (command line), which handles more of this
> stuff for you.  If you'd rather know the gory details:
>
>   Generally speaking, creating a mountable filesystem is a two-step process.
>
>   First, you create a partition for the filesystem to live in.  A
> partition designates a "slice" of the disk for some particular task
> (like holding a filesystem).  Each partition has a type code which
> helps the OS identify what's supposed to be in the partition.  That's
> the type you're seeing in fdisk.  Setting the partition type doesn't
> do anything other than change the "type" field in the partition table;
> it's up to other things to make the contents of the partition actually
> match the type.
>
>   Step two is create the filesystem in the partition.  A filesystem
> contains all the housekeeping information to keep track of files,
> directories, permissions, last-modified-time, free space, and so on.
> Under *nix, one generally uses the some kind of "mkfs" tool to do
> this.  (In the Microsoft world, one uses "FORMAT" for all the
> Microsoft filesystems.)  "mke2fs" creates Linux EXT2 and EXT3
> filesystems.  "mkdosfs" creates FAT and FAT32 filesystems.  "mkswap"
> marks a swap partition (which isn't technically a filesystem, but
> serves the same purpose for this discussion).
>   
I don't want a multiple partitions, just a single FAT32...  So from your 
description above I'd change the partition to "c" FAT32 LBA.  And then 
mkdosfs -F 32 ...
>   If the partition type doesn't match the filesystem you actually
> write to the partition, things may actually still work, depending on
> the OS, the tools you're using, and what you wrote there.  For
> example, the ext2 and ext3 drivers in the kernel don't care what the
> partition table says; they look for a signature in the superblock.
> But tools which look for ext2/3 filesystems to mount for you may only
> look at the partition table.  Microsoft's OSes generally require the
> partition table to be correct, or Bad Things happen.
>
>   
>>  I'm sure which of the million format options available is "FAT32".
>>     
>
>   There are several partition types for FAT32; which one to use
> depends on the disk geometry.  If the disk is big enough that it can
> no longer use CHS (cylinder, head, sector) to address disk blocks, and
> instead *must* use LBA (linear block addressing), FAT partitions get
> different type codes.  (Why?  Because MS-DOS, which Windows 98/ME
> still boot from, couldn't figure it out without help.)
>
>   You have to use the LBA types for partitions located above the
> roughly 8 GB limit of the classic INT13 BIOS interface.  Partitions
> which exist entirely below the 8 GB line use the non-LBA type.  (I
> think.  It's been a long time.)
>
>   According to my fdisk, the non-LBA FAT32 is type 0x0B, while the LBA
> FAT32 is 0x0C (don't enter the "0x" prefix when working in fdisk).
>
>   
My eyes must have glazed over when I saw all the W95 options - they all 
looked the same.  So c looks like the "right" one.  (For "W95 FAT32 
(LBA)). 

So what are options 1b and 1c ???

>   To get an idea of just what a mess this is, you can see the list of
> the approximately 15 different "size barriers" here:
>
> http://www.storagereview.com/guide2000/ref/hdd/bios/size.html
>
> -- Ben
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