EFI System Partition: Difference between revisions

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Revision as of 15:46, 2 October 2022 (view source) Ori (talk \| contribs) m (Clarify the ESP acronym, as it is not directly explained that it refers to the EFI System Partition) ← Older edit		Latest revision as of 10:07, 10 June 2024 (view source) Mintsuki (talk \| contribs) mNo edit summary
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Line 1: The '''EFI System Partition (ESP)''' is a dedicated partition on [[GPT]]. Usually a small one (32-256MiB), located at the beginning of the disk and its partition record at the beginning of the GPT. == Identify == Unlike normal bootable partitions, which have the attribute flag bit 2 set, ESP is identified by ~~it's~~its GUID, which is C12A7328-F81F-11D2-BA4B-00A0C93EC93B == Format == ~~In theory~~The ESP can be formatted to any [[FAT]] file system, [[FAT12]]/[[FAT16\|16]]/[[FAT32\|32]]. InOften ~~reality~~[[NTFS]] ~~most~~may ~~firmware~~also ~~only~~be ~~support~~supported. ~~FAT32,~~There's ~~and~~one ~~some~~notable ~~platforms~~exception, ~~with~~some ~~limited~~older ~~resources~~Apple ~~may~~machines ~~support~~(like ~~[[FAT16]]~~iMac ~~too.~~and ~~[[FAT12]]~~MacBooks) isuse ~~very~~a ~~rarely~~special ~~implemented,~~firmware ~~and~~which ~~it's~~only ~~safe~~accepts to[[HFS+]] ~~assume~~file ~~it won't work~~system on athe EFI ~~real~~System ~~hardware~~Partition. ~~There's one notable exception, Apple machines (like iMac and MacBooks) use a special firmware which only accepts [[HFS+]] file system on the EFI System Partition.~~ == Access == In the EFI Shell, the ESP is the very first file system, denoting as ''FS0:''. [[GRUB]] and [http://elilo.sourceforge.net ELILO] recognize ESP, and they install their files there by default. Other boot loaders, like [http://www.rodsbooks.com/refind/ rEFInd] can only work if ESP exists. From ~~you~~your application, you can use the [[Loading files under UEFI\|EFI_SIMPLE_FILESYSTEM_PROTOCOL]] to access files on the ESP ~~programatically~~programmatically. == Important Files on ESP == * FS0:\STARTUP.NSH - an EFI Shell script, similar to MS-DOS autoexec.bat * FS0:\BOOTMGR.EFI - the EFI boot manager * FS0:\BOOT\~~BOOTX86~~BOOTIA32.EFI - the default ~~x86_32~~IA-32 (32-bit x86) boot loader * FS0:\BOOT\BOOTX64.EFI - the default ~~x86_64~~x86-64 boot loader To avoid filename clashes, you should not create files in the root directory of ESP. The specification mandates that root directory is for vendor directories, like FS0:\APPLE, FS0:\MICROSOFT etc. Some applications (like GRUB) just creates a one level directory without vendor parent directory. Feel free to create a directory for your own OS, and put your files there. Line 34 ⟶ 32: [[Category:Firmware]] [[Category:UEFI]] [[Category:Disks]]