[GTALUG] MBR and GTP Drives

[Lennart Sorensen]

On Mon, Oct 09, 2017 at 10:53:13AM -0400, Scott Sullivan via talk wrote:
> On 07/10/17 08:53 PM, Howard Gibson via talk wrote:
> >     From fdisk, I could see that the Western Digital drive was GTP.  The new Seagate drive identified itself as "dos", which means it is MBR.  Best Buy offered me a newer Seagate at a slightly lower price but one is claimed explicity to support Linux, and it supports some older protocols.  When I told the people at the store I wanted MBR, not GTP, they just stared at me.
> 
> Partitioning is not a property of the hardware, but of the data written to
> it. Manufactures my preformat a disk with MBR or GPT but your under no
> obligation to use it.
> 
> As you've pointed out, you can change it after the fact, but that is a
> destructive operation. MBR and GPT are mutually exclusive. Picking on must
> be done before installation or writing of data you'll want to keep.
> 
> I've developed a habit of zeroing the area where the two partition tables
> may live. Then letting my system boot normally, the install will offer to
> partition the disk appropriately for the type of disk, and manner in which
> we booted (UEFI vs MBR).
> 
> dd bs=1M count=5 if=/dev/zero of=/dev/sdX
> \  \     \       \            \- Your disk.
>  \  \     \       \- A special device file that is infinite zeros
>   \  \     \ 5 blocks worth from 'if', number is larger then needs to be
>    \  \ Copy in block sizes of 1 megabyte
>     \ 'Convert and Copy'

Remember the GPT is at the start AND end of the disk.  You have to wipe
both or the second copy of the GPT may bite you later.

-- 
Len Sorensen