BIOS boot partition: Difference between revisions

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| accessdate = 2014-06-26

| website = gnu.org

}}</ref>

<ref>

{{cite web

| url = https://sourceforge.net/p/gptfdisk/code/ci/master/tree/parttypes.cc

| title = parttypes.cc in the gptfdisk source code

| accessdate = 2023-05-03

| website = gptfdisk project on sourceforge.net

}}</ref> (which, when written to a GPT in the required little endian fields, forms the ASCII string "<code>Hah!IdontNeedEFI</code>").<!-- See talk page for some notes on endianness confusion. --> In the context of GPT on a BIOS-based computer, a BIOS boot partition is similar in some respects to the [[EFI system partition]], which is used by systems based on [[Extensible Firmware Interface|EFI]]. The EFI System partition holds a filesystem and files used by the UEFI, while the BIOS boot partition is used in BIOS-based systems and accessed without a filesystem by holding raw binary code.

The size requirements for a BIOS boot partition are quite low so it can be as small as about 30&nbsp;KiB; however, as future boot loaders might require more space, 1&nbsp;MiB might be a reasonable BIOS boot partition size. Due to the [[1 MB partition alignment|1&nbsp;MiB partition alignment]] policies used by most modern disk partitioning tools to provide optimum performance with [[Advanced Format]] disks, [[Solid-state drive|SSD devices]] and certain [[RAID]] configurations, some room is left allowing the placement of a BIOS boot partition between the GPT and the first partition aligned that way (34&ndash;2047 for 512-byte sectors; 6&ndash;255 for 4096-byte sectors). If created by utilizing that free space, the BIOS boot partition would be out of the GPT alignment specification,<ref>See buthttps://uefi.org/specs/UEFI/2.10/05_GUID_Partition_Table_Format.html, that"GPT ispartitions notshould verybe important{{citationaligned needed|date=Juneto 2017|reason=Whothe sayslarger itof: isGPT unimportant?partitions Isshould thisbe justaligned opinionto orthe islarger itof: declareda in– theThe partitioningphysical standardblock /boundary, bootloader'sif documentation?any; Evenb if– itThe isoptimal *written*transfer tolength rarelygranularity, itif isany."</ref> *read*but everythat boot,is andnot anythingvery thatimportant clobberssince: it(a) willthe preventalignment therule systemis from"should" beingand ablenot to"must" boot.}}(b) sincethe itrule is writtenbased toon a performance consideration, which for a very infrequentlysmall partition used only at system boot bears no real consequence.

== Creation ==

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== External links ==

* [https://www.gnu.org/software/grub/manual/html_node/BIOS-installation.html#BIOS-installation BIOS installation], part of the GRUB2 documentation

* [http://www.funtoo.org/wiki/GUID_Booting_Guide The Funtoo Linux GUID Booting Guide]

* [http://www.rodsbooks.com/gdisk/booting.html Booting from GPT], part of the GPT fdisk documentation

* [http://www.rodsbooks.com/gdisk/bios.html Legacy BIOS issues with GPT], February 22, 2014, by Rod Smith