Re: DD bs=4M option on USB mem-stick creates false format

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

Greg Wooledge wrote:
> If the disk-image came
> from a 4 GB disk, and you write it onto an 8 GB disk, then the 8 GB
> disk will *believe* that it is a 4 GB disk, because it has the metadata
> from a 4 GB disk.

The device size is not determined by the image data which get written to it.
I assume that firmwares and operating systems obtain it by SCSI commands
from the stick hardware.

The device file in Linux is simply a string of the determined number
of blocks.

The partition tables are simply data written to those blocks.
Their block addresses and the meaning of their bytes is subject to
conventions of software producers.

I understand Microsoft and IBM specified the MBR partition table.
Later Intel specified EFI and GUID Partition Table (GPT) as replacement
of BIOS and MBR partition table.
Apple had its own Apple Partition Map. Sun has disklabels. SGI had MIPS
Volume Headers. FreeBSD installs its slices inside MBR partitions.


Have a nice day :)

Thomas