Re: fdisk without mkfs?

["J. Scott Kasten" <jsk titan tetracon-eng net>]

Fdisk only updates some table entries in the frst sector of the drive, it does
nothing to the partitions themselves.  If a new partition happens to start on
the same track as an old partition, the file system there may still appear
to be valid, however, don't trust it!!!  Create the new file system or you'll
likely be sorry later.  A really sorry example is what happens when you
start manuvering around Windows partitions.

Suppose you have a 10GB drive covered by one windows partition as it comes
from the store in a new PC.  You decide to split the drive 50/50 between
windows and Linux, and just choose to do your own custom windows load
after the repartitioning rather than using partition magic or something to
resize it.  Thus you fire up Linux fdisk, delete the old 10GB windows
partition, create a new 5GB windows partion as #1, then add your Linux
and swap stuff in the remaining 5GB.  You spend your next hour installing
Linux, reboot, then start a fresh windows install.  However, you're horrified
to find that the DOS format utility just reformatted the entire 10GB drive
and ruined all your hard work.  Reason: the old windows file system was
still there, DOS/Windows only uses the partition table to locate the
partition starting address, the file system header within the partition
was never touched, DOS gets the SIZE info from there and happily reformats
it's 10GB partition.

Solution: If it's a windows partion that has been adjusted, either use a
tool like partion magic, or use linux to kill it by doing something like
"dd if=/dev/zero of=/dev/hda1 bs=512 count=10" to wipe the partion header
info out so windows is forced to read the partition table to get the
correct size.  For linux or any other os, use a proper mkfs util to do it.

On Sat, Oct 30, 1999 at 03:20:02AM -0700, Todd A. Jacobs wrote:
> I'm a little confused about something. The other day, I fdisked a new
> partition, and then successfully mounted it without running mkfs first.
> The filesystem seemed to work fine, despite the fact that I never actually
> created one. Can anyone shed some light on this for me?
> 
> -- 
> Todd A. Jacobs
> Network Systems Engineer
> 
> 
> 
> -- 
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-- 
J. Scott Kasten

jsk AT tetracon-eng DOT net

"If you stand for nothing, you're likely to fall for anything."