Re: General Linux Laptoppin'

[Bryan J. Smith <b.j.smith@ieee.org>]

Captive is it.

Understand that is it _never_ safe to write to a NTFS filesystem _unless_ you have all of require the meta-data information on it.
In the case of NTm this is the SAM registry with SIDs.

In the NT world, there is _nothing_ like Captive, no way for one NT system to read another's registry.
The most you have is NT5+ using Logical Disk Manager (LDM) disk labels (partition table format, LDM = "Dynamic Disk"), which offers 4 improvements over the legacy PC BIOS ("Basic/Standard Disk").

One feature is the ability to store SIDs in hidden areas of the disk label for a NTFS filesystem.
This allows another NT5+ installation to read these all-important SID info,
so it can safely write to a NTFS file system without having the same SAM registry.
Now the info doesn't guarantee you won't screw up the meta-data (e.g., ACLs, etc...),
but it _does_ prevent one NT installation from corrupting the NTFS filesystem used by another.

The Linux NTFS/LDM project is working hard to implement this feature as well.
LDM is an important support requirement for dual-booting, especially since LDM solves the LBA32/ATA48 geometry issues were starting to see
(especially with buggy BIOSes where NT4SP4-NT5.1 just ignore the Int13h geometry).
With LDM, Linux can read the exact geometry assumed by NT (especially for >137GB drives), and the explicit SID info for a NTFS filesystem,
allowing safe writting to the disk label (partition table) as well as any NTFS filesystems in it.

Until then, the kernel has to make assumptions on geometry,
ones where NT4SP4-NT5.1 conflicts with new >137GB ATA48 / Int13h Extended geometry
(as well as some of its own versions, let alone DOS/Win9x).
And it has to rely on user-space tools like Captive, that reads the registry to discover SAM/SID info so it can safely change meta-data structures on a NTFS filesystem.

These are not Linux issues, but a core BIOS/NTFS design issues,
ones where Microsoft can only accomodate by moving to a new partition table format for NT itself.


-- 
Bryan J. Smith (currently mobile)
b.j.smith@ieee.org

-----Original Message-----
From:  Casey Boone 
Date:  05-2-1 8:56
To:  silug-discuss@silug.org
Subj:  Re: General Linux Laptoppin'

the only user space driver i am aware of uses microsoft's own ntfs drivers

are you thinking of something other than captive ntfs?

Casey


On 31 Jan 2005 15:37:54 -0800, Bryan J. Smith <b.j.smith@ieee.org> wrote:
> Linux can write NTFS.
> It just won't by default because it's dangerous to do so from any OS installation (even NT), except the one that created it with its SAM/SIDs.
> There is a user-space driver for Linux that reads the SAM/SIDs so it can safely do so.
> 
> --
> Bryan J. Smith (currently mobile)
> b.j.smith@ieee.org
> 
> -----Original Message-----
> From:  Robert Citek
> Date:  05-1-31 14:18
> To:  silug-discuss@silug.org
> Subj:  Re: General Linux Laptoppin'
> 
> On Monday, Jan 31, 2005, at 16:03 US/Central, Ray Holtz wrote:
> > Then a minute later I took a regular Windows XP CD and did a complete
> > reinstall of XP.  I put XP on a 40% partition with NTFS, made a 10%
> > fat32 partition, then a day or two later installed Redhat 8 on the
> > other 50% of the drive.  The fat32 partition is a nice spot to place
> > files you want to be writable to both OSes.  Even though Linux can
> > read NTFS it can't write to it, so the Fat32 partition comes in handy
> > so I can work with files from both sides of the hard drive.
> 
> You can probably do away with the fat32 since Windows can read ext2/3
> (not write) and Linux can read NTFS (not write).  BTW, Mac OS/X can
> read and write to ext2.  More info:
> 
>    http://www.cwelug.org/cgi-bin/wiki.cgi?Filesystems
> 
> Regards,
> - Robert
> http://www.cwelug.org/downloads
> Help others get OpenSource.  Distribute FLOSS for
> Windows, Linux, *BSD, and MacOS X with BitTorrent
> 
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