[hfs-user] Partition and Boot block Structures in a HFS CD image

Simon Bazley sibaz@sibaz.com
Tue, 26 Feb 2002 14:51:32 +0000

I'm not sure about the partition stuff, Floppy disks don't need
partition info, so I'd guess you don't need it on a CD either, but I may
be wrong.
Both HFS and HFS+ state that the MDB (or VDB) must reside at sector 3
(sector 2 if you start with 0) and that sectors are 512 bytes.
The bit before that should contain the device driver, for the hard disk,
which I'm assuming will be ignored if its all zero's (and hence not
My understanding is that a device may have a driver and not be bootable
(as the system files are stored elsewhere in HFS+), in which case you're
just loading a driver to read the disk.  I guess that in HFS+ you could
have no device driver, but still have a system file, and hence be
bootable on modern macs.
Its a pretty sure bet though that 0's indicate no driver and no bootable
disk on HFS.  Floppy disks have zeros for the first 2 sectors.  Checkout
flexiblebtree from sourceforge and look at the diskimage.img file, it is
an example of a floppy disk as produced by a mac.  Use the BinList
application to list the first 3 sectors and you'll see 2 sectors of
zeros and 1 with a MDB in it.


Biswaroop Banerjee wrote:

>  Hi all,   Can anybody give me a judgement??  If i am creating a file
> which contains a HFS filesystem image which will be then written to a
> CD.  THis image is not a Bootable Cd so should the file contain
> partition and boot block structures.  Should i just write "zeros" in
> the first two sectors of the image (i.e. 512 *2 = 1024 bytes) in the
> file, and then write down the MDB structure in the image file
> after 1024 bytes??  Waiting for replies..  regards  Biswaroop
> Banerjee