On Wed, Sep 05, 2001 at 08:46:08AM -0400, Declan Moriarty wrote:
> On Tuesday 04 September 2001 14:31, you wrote:
> > Tom Oehser wrote:
> > > > > idea in backing up all the empty space.
> > > >
> > > > How about compression? Isn't the empty space zeroed?
> > >
> > > No. It is full of detritus. Deleting a file just flips a bit in the
> > > directory. You have to make a big file of zeros that fills it if you
> > > want to dd a partition efficiently.
> >
> > Hmm. That might not be that bad of a thing to have to do. Mount
> > the partition at /mnt/C then do cat /dev/null> /mnt/C/ZEROES.000
> > until it fills up, then unmount it, then do the dd into gzip into backup
> > media.
>
> I take your correction about /dev/null being /dev/zero. I was just thinking
> "What does he know that I don't?" I always saw /dev/null as the linux
> equivelant of the Write Ony Memory, whose datasheet I still have
>
> That aside, why bother what is on the disk? In a FAT system, the disk gets
> filled from end to end, bits get wiped in the middle by a user deleting, and
> then it gets filled again. If you dd, you get the entire disk, whether it's
> full or not; if you use cp or tar, you just get the files.
Zeroing out unused areas of the hard drive give you a consistent data
pattern in them. This makes compression much better.
If you use cp or tar, you may have problems with file permissions, as
Mess-DOS file permissions don't map nicely to Unix ones. This is also
a potential problem with Samba backups.
Also, make danged sure you get the registry, system.dat and user.dat
in \windows. They are hidden and system files, and must be present for
the system to run.
Have we got enough here that I can write up a tech note for Linux
Journal? I'll give proper credit, of course.
>
> --
> Regards,
>
>
> Declan Moriarty
>
>
>
>
> Applied Researches - Ireland's Foremost Electronic Hardware Genius
>
> A Slightly Serious(TM) Company
>
> Success covers a multitude of blunders - G.B. Shaw.
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