Re: Partition 1 does not end on cylinder boundary
From: Rod Smith (rodsmith_at_nessus.rodsbooks.com)
Date: 04/10/04
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Date: Sat, 10 Apr 2004 13:16:56 -0400
In article <facb01db.0404092147.bf3bd9e@posting.google.com>,
rdgentry1@cablelynx.com (P Gentry) writes:
>
> rodsmith@nessus.rodsbooks.com (Rod Smith) wrote in message news:<rmj55c-e0m.ln@speaker.rodsbooks.com>...
>
>> 2) DOS/Windows FDISK can't "see" non-FAT logical partitions in an
>> extended partition. I've never seen FDISK overwrite or wipe out
>> such partitions, but I don't believe I've ever deliberately tried to
>> make that happen, either.
>
> FDISK simply states "non-DOS partition" as the type.
That's how FDISK displays non-FAT *PRIMARY* partitions. FDISK, at least
in Microsoft products and in my experience, simply doesn't display
non-FAT *LOGICAL* partitions as existing at all. I just checked this on a
system running Windows Me; when I used FDISK to display the logical
partitions on the disk, it showed the D: FAT partition, but not the half
dozen or so non-FAT logical partitions that are on the disk. (FreeDOS's
FDISK, though, seems to display non-FAT logical partitions. I can't check
DR-DOS's FDISK at the moment, but I recall it being like Microsoft's
FDISK on this score. I've never used PC-DOS, so I can't comment on its
FDISK.) I've seen numerous posts from people who want to delete non-FAT
logical partitions from DOS or Windows but who can't, at least not using
DOS/Windows' FDISK.
>>> Word to the wise -- do _not_ mix MS and non-MS partitions in the
>>> extended partition!
>>>
>>> In an extended partition with non-MS table entries, a Win based disk
>>> util will likely as not trash your tables or actually _zero_ areas of
>>> a neighboring partition
...
> I know _exactly_ what caused my problems -- FDISK! It begins zeroing
> sectors _before_ you give it the final go ahead! And there is no way
> to back out or recover when you get the message "Unable to delete
> partition" -- you're already toast. But your Win partition has been
> strangley resized/enlarged.
In which case, cautioning against using both Microsoft and non-Microsoft
logical partitions in an extended partition is overkill; you should
instead caution against the use of FDISK on disks that are so
partitioned. I wouldn't disagree with such advice, either; the
DOS/Windows FDISK program is woefully inadequate for any multi-OS
configuration. Your advice against mixing Microsoft and non-Microsoft
logical partitions presents an overly-broad picture of the risk, which
can lead people to jump through potentially more troublesome or dangerous
hoops to avoid a problem that's much more easily avoided by not using
DOS/Windows' FDISK. For instance, somebody might read your advice and buy
multiple disks or try to cram Linux exclusively onto primary partitions
(limiting the number of partitions, which could lead to additional effort
when doing a major upgrade or even lost data if the user forgets to back
something up when doing such an upgrade). I'm all for exercising caution,
but presenting very cautious advice without the reasons for the caution
can be as bad as or worse than presenting no or even recklessly
UNcautious advice.
>> > If you _must_ muck around with partitions on an existing dual boot
>> > installation, I highly recommend parted to fdisk or sfdisk
>>
>> Ordinarily I have no qualms with parted, but given the fact that I've
>> seen it do odd things with CHS geometries, I'm a bit wary of using it on a
>> disk that's already displaying such problems. My hunch is that it might
>> just restore the original Linux CHS geometry, and when the OP goes to
>> install Windows again, it'll convert it back to its own values. That's
>> just a guess, though.
>
> You seem to labor under the illusion that CHS is somehow
> _standardized_.
I'm under no such illusion; it's just that, to avoid problems, it helps
if all your OSs and tools use the same CHS geometry for a specific disk,
and GNU parted sometimes doesn't agree with other tools, which can cause
problems. As the OP's already got inconsistencies on this score, it seems
to me that parted is more likely than usual to cause further problems.
-- Rod Smith, rodsmith@rodsbooks.com http://www.rodsbooks.com Author of books on Linux, FreeBSD, and networking
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