Re: Differences in Primary GPT Header

[Jim Meyering]

Tobias Arp wrote:
> i am using parted  2.1 aand i have some questions about gpt partitions.
> I have created a gpt partion on a harddisk. After creating a ntfs file system 
> on this partition i got full access to this drive.
> I could read and write successfully on it.
> I viewed the primary gpt header on my linux computer and printed it.
> Then i put this harddisk on my windows 7 pc. The harddisk is detected 
> successfully and i can access all files.
> But  after having the drive in my windows computer changes are made to the 
> primary gpt header.
>
> Following values aree changed:
>
> Offset 0x20 = Backup LBA
> Offset 0x30 = Last usable LBA
>
> Both are decreased for about 30 sectors.
> Windows does it.

Thanks for the report.

> When i look into the documentation of gpt partitions it seems to be right 
> what windows has done.

Why?

Please provide more information, e.g., the output of this:
(assuming your disk is /dev/sda)

    # parted -s /dev/sda u s print free

That will tell us the size in sectors of your disk.

Then tell us the actual values from your primary table by running this:
(again, assuming /dev/sda)

    # od -w8 -Ad --skip=$((512+32)) -N24 -td8 /dev/sda