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Scenario: BIOS computer (Not EFI) HDD with GPT partition table

I'm trying to follow these instrutions: https://wiki.archlinux.org/index.php/GRUB#GUID_Partition_Table_.28GPT.29_specific_instructions

I want to know if what i've done is correct:

Parted report:

mint@mint ~ $ sudo parted /dev/sda unit s print
Model: ATA TOSHIBA MK6476GS (scsi)
Disk /dev/sda: 1250263728s
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start       End          Size        File system     Name                 Flags
 1      34s         2047s        2014s                       BIOS boot partition  bios_grub
 2      2048s       526335s      524288s     ext2            Linux filesystem     legacy_boot
 3      526336s     34080767s    33554432s   linux-swap(v1)  Linux swap
 4      34080768s   570951679s   536870912s  ext4            Linux filesystem
 5      570951680s  1250263039s  679311360s  ext4            Linux filesystem

Gdisk report:

mint@mint ~ $ sudo gdisk -l /dev/sda
GPT fdisk (gdisk) version 0.8.8

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.
Disk /dev/sda: 1250263728 sectors, 596.2 GiB
Logical sector size: 512 bytes
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 1250263694
Partitions will be aligned on 8-sector boundaries
Total free space is 655 sectors (327.5 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1              34            2047   1007.0 KiB  EF02  BIOS boot partition
   2            2048          526335   256.0 MiB   8300  Linux filesystem
   3          526336        34080767   16.0 GiB    8200  Linux swap
   4        34080768       570951679   256.0 GiB   8300  Linux filesystem
   5       570951680      1250263039   323.9 GiB   8300  Linux filesystem

Thank you in advance!

1 Answer 1

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Yes your partitions are aligned correctly.

The way you can tell is to divide the start sector of each partition by 8. If you wind up with a whole number, it's aligned. If you get a decimal point, then it's not aligned. The only exception is the 1st partition. It's not aligned but it doesn't matter since that's your EFI partition (madatory on GPT disks).

So why divide by 8? For years hard drives had a sector size of 512 bytes (1/2 KB). In recent years, the sector size has increased to 4 KB, but for compatibility purposes it still reports 512 byte sectors. A 4KB physical sector represents eight logical (virtual) sectors.

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  • You're correct on everything but one small detail: The first partition is a BIOS Boot Partition, not an EFI (System) Partition (ESP). Neither a BIOS Boot Partition nor an ESP is required on GPT disks, although the former is helpful when using GRUB on a BIOS-bootable GPT disk, and the latter is needed to boot in EFI mode. Alignment on a BIOS Boot Partition is unimportant. It could make a difference on an ESP, but not much of a difference.
    – Rod Smith
    Jul 31, 2014 at 19:51

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