Re: USB3 3TB HDD boot

[Chris Murphy]

On Mar 15, 2013, at 8:51 AM, Lennart Sorensen <address@hidden> wrote:

> On Thu, Mar 14, 2013 at 08:56:18PM -0600, Chris Murphy wrote:
>> Right, for a 4Kn drive, to read LBA 1 and get the GPT header I'd need:
>> 
>> sudo dd if=/dev/disk3 skip=8 count=1 2>/dev/null | hexdump -C
> 
> Wouldn't using 'bs=4096' make things simpler and more obvious?

How would it?

These structures are still predicated on a 512 byte block. The MBR is always 
512 bytes, but on a 4096/4096 4Kn drive, LBA 0 is 4096 bytes. So if I don't 
want to see 3584 bytes of useless garbage, I can't set the dd block size to 
4096, or I get extra information.

If I want to see just the GPT header, which while only ~92 bytes, by spec it 
gets its own sector, there's far less superfluous information using a bs of 512 
bytes than 4096 bytes.


Chris Murphy