[ILUG] Mounting XP Partition

[Rick Moen]

Quoting Ciaran Johnston (cj at nologic.org):

> The "ro" part means read-only. I don't know what kernel you have, but
> allowing write access to ntfs can be dangerous - I'm not sure it even
> works fully.

NTFS writing from Linux _was_ briefly dangerous because of recklessly
written code in the older (now obsolete), original NTFS filesystem
driver.  There's a persistent misconception that that situation still 
exists, although it's long gone.

Some time around 1995, Martin von Löwis wrote the older driver with
write-mode support included, and made two serious design errors:  (1)
The driver wasn't SMP-safe, and (2) it didn't bother to check the NTFS
filesystem's version string before writing to it.  (It was written to 
cope with the then-current v1.2 NTFS format used by NT4.)  Worse, the
author then orphaned his code.

Shortly after that (around year 2000), Win2k and then WinXP came out
with revised NTFS version specs -- NTFS versions 3.0 and 3.1,
respectively.  The old driver, making the catastrophic assumption that
its understanding of NTFS filesystem semantics was good for all time,
blithely wrote its data to disk using v1.2-filesystem assumptions, and
thereby corrupted entire partitions.  Thus the perception, which
persists to this day, that Linux NTFS write-mode is dangerous.


Over the last couple of years, Anton Altaparmakov of the Linux-NTFS
Project wrote a completely new, from-scratch driver implementation that
avoided the old one's errors and was duly cautious in the areas where
the old one was reckless:  It's SMP-safe and carefully checks filesytem
versions before doing anything.  (Moreover, it understands all NTFS
versions issued to date.)  _Also_, Altaparmakov went back and patched
the older driver to insert safeguards, so that it would (appropriately)
refuse to write to post-v1.2 NTFS filesystems.

The new driver was introduced with the 2.5.11 beta kernel and fully
released in the 2.6.x production series, but also has been backported to
2.4.x.  

Because Altaparmakov is being extremely cautious, write mode is subject
to some stringent limitations while broader functionality is being
tested for safety:  At the moment, the new driver's write support is
willing to alter-in-place existing files on NTFS, but will balk at
changing a file's length, or adding or deleting existing files.  Those
limitations may make write mode effectively useless for (say) dual-boot
file-sharing, but at least it's good enough for recovering lost
Administrator passwords -- and _definitely_ is well-tested and safe.

Whether any arbitrary Linux installation's NTFS write support (if any)
is safe depends, of course, on which driver is present.  The Linux-NTFS
Project's "status" page may be helpful in that area:
http://linux-ntfs.sourceforge.net/status.html

-- 
Cheers,               No trees were destroyed in the sending of this message. 
Rick Moen             We do concede, though, that a large number of electrons 
rick at linuxmafia.com   were terribly inconvenienced.