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SubjectRe: Linux & FAT32 label
On Monday 20 November 2017 12:12:56 Karel Zak wrote:
> On Sun, Nov 19, 2017 at 01:44:40PM +0100, Pali Rohár wrote:
> > On Thursday 09 November 2017 22:21:31 Pali Rohár wrote:
> > > So from all tests and discussion I would propose new unification:
> > >
> > > 1. Read label only from the root directory. If label in root directory
> > > is missing then disk would be treated as without label. Label from
> > > boot sector would not be read.
> > >
> > > --> Reason: Windows XP and mlabel ignores what is written in boot
> > > sector. Windows XP even do not update boot sector, so label
> > > stored in boot sector is incorrect after any change done by
> > > Windows XP.
> > >
> > > This logic is used by all tested MS-DOS and Windows versions,
> > > plus also by mtools on Linux.
> > >
> > > 2. Write label to to both location, boot sector and root directory.
> > >
> > > --> Reason: MS-DOS 6.22, MS-DOS 7.10, Windows 98 and also mtools on
> > > Linux do this. This is also what is written in FAT specification.
> > >
> > > It also provides backward compatibility with old dosfslabel
> > > versions which read label only from boot sector.
> > >
> > > 2. Process 'NO NAME ' label in root directory as 'NO NAME' name. Not
> > > as empty label.
> > >
> > > --> Reason: 'NO NAME ' is regular entry in root directory and both
> > > Windows XP and mlabel handle it in this way.
> > >
> > > 3. Process 'NO NAME ' label in boot directory as empty label. Not as
> > > label with name 'NO NAME'.
> > >
> > > --> Reason: On Windows XP when formatting empty disk and label is not
> > > specified then 'NO NAME ' is stored to boot sector.
> > >
> > > Also in FAT specification is written that empty label is stored
> > > as 'NO NAME '.
> > >
> > > With this change we would get compatibility with MS-DOS, Windows (both
> > > DOS-based and NT-based) and also with Linux mtools, modulo problems DOS
> > > code page.
> > >
> > > There are just two negatives:
> > >
> > > 1) Labels set by old dosfslabel versions (which stored them only to boot
> > > sector) would not be visible. But they are already not visible on
> > > MS-DOS or Windows machines, and also via mlabel (from mtools).
> > >
> > > 2) Behavior of blkid and fatlabel would be changed as both tools have
> > > different as proposed above, and based on tests they also differ each
> > > from other.
> > >
> > > Andreas, Karel, what do you think about it?
> >
> > Also for other people, do any have comments on my proposed solution?
>
> Go ahead and send patch :-) (also with LABEL_FATBOOT=)

Now I implemented changes for dosfstools project, pull request is there:
https://github.com/dosfstools/dosfstools/pull/73

Just waiting for the Andreas response...

Andy, you wanted some manpage update. I did it in this commit:
https://github.com/dosfstools/dosfstools/pull/73/commits/3f4f122b7ec8eeb4a0ae0db8e94b8829f51d1163
Can you check if changes in manpage are OK?

--
Pali Rohár
pali.rohar@gmail.com

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