Ed G. schrieb:
> > I would never use dd to copy complete installations unless the discs
> > were identical and the machines' BIOSes had the same idea of the disc
> > geometry. YMMV.
>
> When I did my "brain transplant" from my old to my new PC I was
> very concerned about this, especially since many people, like you,
> cite disk geometry as the reason why one can't simply use dd to
> copy partitions.
>
> Having given the matter more thought, I wonder if the disk geometry
> argument isn't specious. I would expect disk geometry to be a
> spoiler only if C/H/S addressing were embedded in the partition
> data, e.g, if individual clusters were identified by their C/H/S
> coordinates.
>
> This is not the case with Linux, nor as far as I know Windows 98,
> which both use logical block addressing rather than C/H/S. As far
> as I know this is not the case with DOS either: C/H/S values are
> present in only one place, namely the partition table while the dos
> partition itself uses logical addressing to identify clusters.
>
> This would seem to imply that so long as you make byte for byte
> copies of the individual partitions rather than the whole disk (e.g.,
> hda1, hda2, hda3 instead of hda), disk geometry shouldn't be an
> issue. This is born out by my experience copying individual dos
> partitions to linux files e.g, by using:
>
> dd if=/dev/hda1 of=dos_partition.raw
>
> I am able to mount these files via the loopback device and access
> the contents of the dos partition without a problem. Since files
> don't have any "disk geometry", let alone the "right" one, this
> shouldn't work, it seems to me, if what people say about disk
> geometry were really true.
>
> I don't mean to be rude, but I really don't see why disk geometry is
> an issue. Perhaps you can help me understand why it is. Have I
> missed something? Have you personally had bad experiences
> using dd to copy partitions?
This is a good idea. Can I make a 500 MB partition(with the batch version
of fdisk: sfdisk) on any HD with
at least 500 MB and than dd a 500MB partition installed on
an other HD. If this is possible, must the partition start at the
same logical sector as on the original install. The question is
how are the sectors addressed within the FS (ext2, OS/2 HPFS,
DOS FAT, NTFS), relative to the start of the partition or with
absolute values. I think they use absolute values because
partition moving tools like partition magic must know the FS
of the moved partition.
An other question:
Have somebody used a CDR with tomsrtbt? For me it is not
importend to have a filesystem on the CD. A raw dd from
my partition would be good for backup reasons. OK, if I have
a full installed Linux system I can use that. However, if I
can go to a friend with a W95 System :-( I connect an
ATAPI CD-Writer , insert my special CDR tomsrtbt and
start an backup of his partition (If the compressed image
has only 500 MB). For this reason a HD filed with zero's is
a good idea as Pierre mentioned.
I than can leave a tomsrtbt restore disk with a automatic
restore script for him. If something gets broken, he put
the disk and CDR I created into the PC and starts.
If the CD has a filesystem:
mount /dev/hdc /cdrom
dd if=/cdrom/imageofw95 | gzip -d9v | dd of=/dev/hda
Or if a raw write to the CDR is possible and there is
no filesystem nessesary:
dd if=/dev/hdc | gzip -d9v | dd of=/dev/hda
This way all filesystems (HPFS, NTFS or other)
can be backuped. There is no need for support
for this filesystem in the kernel.
With netcat and an linux box connected to the net
this creating process must be possible.
Bye
Robert Risch
