[Parted-maintainers] Bug#380226: libparted does not resize NTFS

[David Cantrell]

On Mon, 2007-01-22 at 22:51 +0100, Frans Pop wrote:
> Hello David,
> 
> First of all, thank you for your interest in helping solve this.

Apologies for it taking so long.  The GNU parted team has shifted around
a bit in the past year or so.

> On Monday 22 January 2007 22:01, David Cantrell wrote:
> > libparted does not resize NTFS at the moment, so it's not the cause of
> > the problem.  But I'm not sure what you are using libparted with.  What
> > software are you using that invokes libparted?  Where can I find the
> > source for it?
> 
> Correct. We use ntfsresize to resize the file system. The only thing we 
> need libparted for is to resize the physical partition the NTFS file 
> system is on.
> 
> The actual resize operation is done in the following steps:
> - run ntfsresize to determine if the NTFS partition is clean and what the
>   range is it can be resized to
> - ask user for new partition/file system size
> - if smaller than current, resize NTFS file system using ntfsresize
> - resize physical partition using libparted
> - resize NTFS file system up to new size of physical partition
> 
> This procedure works fine for pre-Vista NTFS partitions.
> With Vista partitions the issue we currently have is that Windows for some 
> reason no longer creates the partition starting on the second sector of 
> the disk and that libparted, because of the current constraints, changes 
> the starting sector of the physical partition which, of course, makes the 
> file system inaccessible.

That's right.  On DOS disk labels, the starting primary partition was
always aligned to sector 0x3F (or 63), but Vista has changed that to
accomodate large disks.  Vista now aligns to sector 0x800 by default
(2048), but it's actually configurable by the administrator.
Unfortunately, it will only present more problems for people like you
and me down the road.  The best we can do is accomodate other operating
systems as much as possible.  See this for more information:

http://support.microsoft.com/kb/923332

> The software we use for this in the installer is a fairly complex beast 
> called partman, which consists of various components. Most of it is 
> scripted, but the interaction with libparted is done through a program 
> called parted_server.

The parted(8) interactive program that comes with GNU parted can do what
you are describing in the above steps.  But you cannot do a partition
resize since resize via parted(8) is intended to resize the filesystem
and partition in one step.  Since libparted lacks NTFS support, we
prevent the user from doing that.

But you can remove the partition and recreate it with a higher end
boundary, which effectively resizes the physical partition for you and
then you can run ntfsresize on that.

When resizing a Vista NTFS partition, be sure to start at sector 2048.
In the parted(8) interactive program, this can be done by specifying
1049kB as the starting location.  See command_line_get_sector() in
parted/ui.c to see how 1049kB is translated to the correct starting
sector.  See do_mkpart() in parted/parted.c to see how to add a
partition using libparted.

I think you could modify you parted_server program to work with these
limitations in mind.

Now, I have made a patch for parted-1.8.2 that will preserve the
starting sector of 2048 on Vista partitions when you are creating the
DOS disklabel.  That should be added to the parted package in Debian for
this to work.

Does any of that help?

> P.S. If you would like to discuss this, feel free to look for me on IRC. I 
> am "fjp" on #debian-boot on OFTC.

I am dcantrell on FreeNode in #parted and various other places.  Or
kg6cii on AIM.  Email here.

-- 
David Cantrell <dcantrell at redhat.com>
Red Hat / Westford, MA