Read-only NTFS

I noticed a comment that somebody posted, indicating that Windows cannot
mount NTFS read-only (except in WinXP or later). Unfortunately this is
exactly what I want to do. Does anybody know a way to get around this
limitation.

Cliff

Oh, sure you can do it. Just simply build a disk filter and a file system
filter (ah, I love waving the magic wand). The file system filter rejects
ALL user level write requests. The disk filter then caches any writes to
the media off to the side and satisfies subsequent read requests from that
cache on the side. When you reboot, discard that “cache on the side”

There is the trick of how to deal with memory mapped files, because if you
don’t prohibit them up-front (but instead reject the paging I/O operations)
you will get the lost-delayed-write-data popup messages. It is best if you
can just prohibit these entirely. For example, you could try stripping out
write access requests on files as the request is passed down (if you reject
it you will fail applications that ask for too many rights but never use
them. Stripping it out, though, will prohibit write operations, including
mapping a file for write access.) I believe that this approach will work,
but I’ve never personally implemented it.

But yes, you can eventually make this work. It is a very large effort and
unless you have a HUGE installed base, you’d be better off buying a bulk set
of XP licenses and upgrading everyone.

Regards,

Tony

Tony Mason
Consulting Partner
OSR Open Systems Resources, Inc.
http://www.osr.com

-----Original Message-----
From: xxxxx@telus.net [mailto:xxxxx@telus.net]
Sent: Monday, June 02, 2003 6:19 PM
To: File Systems Developers
Subject: [ntfsd] Read-only NTFS

I noticed a comment that somebody posted, indicating that Windows cannot
mount NTFS read-only (except in WinXP or later). Unfortunately this is
exactly what I want to do. Does anybody know a way to get around this
limitation.

Cliff


You are currently subscribed to ntfsd as: xxxxx@osr.com
To unsubscribe send a blank email to xxxxx@lists.osr.com

I ran into the same problem. Someone from OSR (Tony?) suggested some
kind of filter.

I use a file system filter that block write/append/delete access to the
FileObject. This filter however cannot block write operations to
“\\.\”. Maybe I do something wrong here.

About the disk filter. I dont know how to do it. So for all disk write
requests, I set
IoStatus.Staus = STATUS_SUCCESS
IoStatus.Information = Parameters.Write.Length
and complete the request without writing the data.
Everything seems to work ok.

Chu Bun

wrote in message news:xxxxx@ntfsd…
>
> I noticed a comment that somebody posted, indicating that Windows cannot
> mount NTFS read-only (except in WinXP or later). Unfortunately this is
> exactly what I want to do. Does anybody know a way to get around this
> limitation.
>
> Cliff
>
>
>
>

Send writes to the bit bucket. For temporary reasons, this is enough.

Max

----- Original Message -----
From:
To: “File Systems Developers”
Sent: Tuesday, June 03, 2003 2:18 AM
Subject: [ntfsd] Read-only NTFS

> I noticed a comment that somebody posted, indicating that Windows
cannot
> mount NTFS read-only (except in WinXP or later). Unfortunately this
is
> exactly what I want to do. Does anybody know a way to get around
this
> limitation.
>
> Cliff
>
>
>
> —
> You are currently subscribed to ntfsd as: xxxxx@storagecraft.com
> To unsubscribe send a blank email to xxxxx@lists.osr.com