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Re: Problem installing Debian 1.3

<tko@westgac3.dragon.com> wrote:

 > Thanks, the thought here is that if a partition is a primary Linux
 > partition rather than a Linux partition sitting in a DOS extended
 > partition, perhaps a virus looking for DOS partitions will leave the LINUX
 > partitions alone. Whereas, viruses would recognise the extended partition
 > as a DOS partition and reek havoc on the DOS, thus trashing any Linux
 > partition residing within.

 > Thus a rescue floppy might allow you to at least recover Linux.
 > Any thoughts on this?

  I think I detect some confusion here - if not, I apologise for
explaining the obvious.  A Linux partition "sitting in a DOS extended
partition" can only exist if the extended partition has a DOS (FAT)
filesystem, with umsdos installed to it.  I presume this is not what you

  In general, extended partitions are not linked to DOS in any way.  An
entry for an extended partition in the MBR's partition table points to
*a second partition table* in a secondary MBR, somewhere else on disk.
This table can contain up to two entries: one for a normal partition (of
any type - e.g. DOS, type 6, or Linux, type 83) and an optional extended
partition entry that points to the next partition table.  (If this means
anything to you, this system resembles a linked list).

  As you can see, if Linux is installed to an extended partition, it
will have a partition of type 83, as usual - you just won't find it in
the MBR, but in some extended MBR somewhere.  If a virus is specifically
looking to destroy a _DOS_ filesystem it won't touch Linux (it wouldn't
go through the partition table anyway, it doesn't need to).  Of course,
if it destroys the information on where the partitions reside (i.e., the
partition table of the MBR of any subsequent extended MBRs), then Linux
won't be able to find the partition it is installed to anymore and can't
boot.  This could theoretically be fixed by booting from a recue floppy
and restoring the partition structure to it's original state.


Gertjan Klein <gklein@xs4all.nl>
The Boot Control home page: http://www.xs4all.nl/~gklein/bcpage.html

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