[parted-devel] How large is a GPT?

[Jim Meyering]

Phillip Susi wrote:
> On 12/28/2011 05:50 PM, Håkon Løvdal wrote:
>> Since the first partition starts at 1MB there is space available in front
>> of this, so I want to create this BIOS Boot Partition so that it starts
>> right after the GPT and spans up til the start of the /boot partition.
>
> FYI, you shouldn't need a dedicated /boot partition.

True, but it can be useful.

>> So my question then is, how do I find the exact size of the GPT?
>> Should I leave some free space between the GPT and the BIOS
>> Boot Partition, and if so how much?
>
> The GPT is usually in the first 64kb so you can create a bios_grub
> partition between sector 129 and 2048.

64kb is not large enough on a disk with 4KB sectors.

Technically, the primary GPT header occupies sectors 1..33 of
your disk.  The 0'th sector is the so-called protective MBR.
That means you can start the BIOS boot partition at sector 34,
aka "34s".  With parted, that "34s" notation works regardless
of whether you're using a drive with 512-byte sectors (most common)
or a newer one with 4k-byte sectors.

If you'd prefer to make your BIOS boot partition start on a more
even boundary, you can leave a gap so that you start it on say,
sector 128, or 256, etc.  However, that does leave a gap that shows
up as being free.  Shouldn't matter, but you never know...