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Msdos hidden files viewable from linux?




On Tue, 24 Oct 1995 mchale at zk3.dec.com wrote:

> Is there a way to get the hidden files on an msdos partition viewable?
> the files are on a large hard drive;
> I looked at mtools but it cautions about using it on hard drives, and
> it didnt seem to be what I wanted.
> 
> I'm trying to backup the dos partion using tar..
> thanx
> -jim
> 
> 

Just a note on what you are trying to do. I backup both my DOS and Linux
hard disks to Q150 cartridge tape using gnutar. In the case of DOS I use
the ASPI (SCSI) tar port of gnutar. The Tar program ignores the DOS hidden
files. This at first concerned me until I searched my DOS disc for hidden
files ( dir /a:h /p /s) and discovered that on my system the only hidden
files were the system IO.SYS and MSDOS.SYS files. These are files you
would never backup but would be contained on a system rescue floppy. 
Incidentally, with Linux you can mount your DOS disc as a DOS type and view
and manipulate any file except hidden ones as if they were Linux (Unix)
files. In fact you can backup your files under DOS and restore them under
Linux using gnutar and the mounted disc (file system). If you need to
backup an unusual hidden file, you can change it to a normal one with the
DOS ATTRIB command. and convert it back later.

Barry

; Thu, 26 Oct 95 00:58:39 -0000
Date: Thu, 26 Oct 95 00:25:00 -0000
Message-ID: <8ebc506 at bilow.bilow.uu.ids.net>
From: mikebw at bilow.bilow.uu.ids.net (Mike Bilow)
Subject: Msdos hidden files viewable from linux?
To: linux-sig at bcs.org
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Albert Cahalan wrote in a message to Mike Bilow:

 AC> Note that it is _impossible_ to correctly backup and restore
 AC> DOS system files without low-level disk access (read:
 AC> dangerous).  The system bit means that the file is sensitive
 AC> to it's physical position on disk.

The "system" bit does not imply this.  In fact, as of DOS 4.0, only
IO.SYS/IBMIO.COM was sensitive to physical location, and only the first cluster
of it.  MSDOS.SYS/IBMDOS.COM was also sensitive to physical location in DOS 3.3
and earlier.  COMMAND.COM has never been sensitive to physical location.

Worse, several DOS-based copy-protection schemes, such as Everlock, depend upon
storing information about the physical location of files which do not have the
"system" bit set or any other special marking present.  As a result, backing up
and restoring a program which uses the Everlock copy-protection scheme will
prevent it from working, one of the things which has contributed to its demise.

 AC> As far as I know, you
 AC> can't back up and restore /boot or the kernel either,
 AC> because lilo gets confused.  The same goes for msdos.sys and
 AC> io.sys.  Maybe someone could write a program to fix the boot
 AC> sector to point to these files.

DOS 4.0 and later actually works pefectly well if you clear the "hidden" and
"system" bits from IO.SYS and MSDOS.SYS.  You can even copy IO.SYS, MSDOS.SYS,
and COMMAND.COM to a blank floppy and it will be bootable, as long as IO.SYS
and MSDOS.SYS occupy the first two records of the root directory and IO.SYS
starts in the first logical cluster of data space.  The SYS.COM program makes
sure that these conditions hold in addition to just copying the files.
 
-- Mike





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