On 28/09/2025 at 11:17, Pascal Hambourg wrote:
However the reported metadata and free space geometries are wrong when the GPT partition entry array does not start at LBA 2: they are reported as if the partition array started at LBA 2, like in the above example. This is confusing and gets in the way of my intent to check if the GPT metadata overlap with the boot loader area.
After some testing and code reading, I understand that the partition entry array will be relocated at LBA 2 on write regardless of the original on-disk PartitionEntryLBA, so the reported metadata geometry reflects what would be written to disk and may be different from the original on-disk metadata layout.
Note: IMO relocating the partition entry array is dangerous if the original partition table layout was carefully crafted to reserve space for the boot loader between the GPT header and the partition entry array: any change to the partition table will relocate the partition entry array and overwrite the boot loader.
What about free space geometry ? Shouldn't it reflect actually usable space and be bounded to the data area (between FirstUsableLBA and LastUsableLBA) ?
