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ESP

ESP stands for EFI system partition.
The ESP is a partition with a FAT file system (FAT12, FAT16 or FAT32, FAT32 is recommended). One ESP must be present in all GPT formatted disks.
Usually, the ESP is around 200-250 MB and resides on a disk's first partition (e.g. /dev/sda1).
The partition code of an ESP is EF02 (gdisk).
parted shows such a partition with the /boot flag. (Note: in a MBR partitioned harddisk, the boot flag has a different meaning).
https://wiki.archlinux.de/title/UEFI_Installation claims that the minimum size of the EFI partition is 512 MiB because FAT32 requires at least that much.
In the Ubuntu family of Linux, the ESP is typically mounted on /boot/efi.

Contents

The ESP contains the boot loader for all installed operating systems, the device drivers and system programs that run before the operating system is started.
This is one of the big advantages of UEFI over BIOS: Every operating system can install the files it needs into the ESP.
On Windows, the ESP can be mounted with mountvol … /s:
C:\> mountvol z: /s
C:\> tree /a
Z:\
└───EFI
    ├───Microsoft
    │   ├───Boot
    │   │   │   BCD                       <- This file can be manipulated with bcdedit.exe (and is referred to as store)
    │   │   │   winsipolicy.p7b
    │   │   │   bootmgfw.efi              <- The microsoft provided boot manager: it loads an OS based on BCD entries. On my current system, this file is binary identical to \EFI\Boot\bootx64.efi
    │   │   │   bootmgr.efi
    │   │   │   kdnet_uart16550.dll
    │   │   │   kdstub.dll
    │   │   │   kd_02_10df.dll
    │   │   │   kd_02_10ec.dll
    │   │   │   kd_02_1137.dll
    │   │   │   kd_02_14e4.dll
    │   │   │   kd_02_15b3.dll
    │   │   │   kd_02_1969.dll
    │   │   │   kd_02_19a2.dll
    │   │   │   kd_02_1af4.dll
    │   │   │   kd_02_8086.dll
    │   │   │   memtest.efi
    │   │   │   boot.stl
    │   │   │   kd_07_1415.dll
    │   │   │   kd_0C_8086.dll
    │   │   │   cbmr_driver.efi
    │   │   │   SecureBootRecovery.efi
    │   │   │   kd_02_1414.dll
    │   │   │   kd_02_15ad.dll
    │   │   │   kd_02_1d0f.dll
    │   │   │   boot.pnd.stl
    │   │   │
    │   │   ├───bg-BG
    │   │   │       bootmgfw.efi.mui
    │   │   │       bootmgr.efi.mui

        …
    
    │   │   │
    │   │   ├───CIPolicies
    │   │   │   └───Active
    │   │   │           {5DAC656C-21AD-4A02-AB49-649917162E70}.cip
    │   │   │           {82443e1e-8a39-4b4a-96a8-f40ddc00b9f3}.cip
    │   │   │           {CDD5CB55-DB68-4D71-AA38-3DF2B6473A52}.cip
    │   │   │
    │   │   ├───ko-KR
    │   │   │       bootmgr.efi.mui
    │   │   │       memtest.efi.mui
    │   │   │       bootmgfw.efi.mui

        …

    │   │   ├───Fonts
    │   │   │       segmono_boot.ttf
    │   │   │       segoen_slboot.ttf
    │   │   │       segoe_slboot.ttf
    │   │   │       chs_boot.ttf
    │   │   │       cht_boot.ttf
    │   │   │       jpn_boot.ttf
    │   │   │       kor_boot.ttf
    │   │   │       malgunn_boot.ttf
    │   │   │       malgun_boot.ttf
    │   │   │       meiryon_boot.ttf
    │   │   │       meiryo_boot.ttf
    │   │   │       msjhn_boot.ttf
    │   │   │       msjh_boot.ttf
    │   │   │       msyhn_boot.ttf
    │   │   │       msyh_boot.ttf
    │   │   │       wgl4_boot.ttf
    │   │   │
    │   │   ├───Resources
    │   │   │   │   bootres.dll
    │   │   │   │
    │   │   │   ├───de-DE
    │   │   │   │       bootres.dll.mui

        …

    │   │   │
    │   │   └───qps-plocm
    │   │           memtest.efi.mui
    │   │
    │   └───Recovery
    │           BCD
    │
    ├───Boot
    │       bootx64.efi                   < On my current system, this file is binary identical to \EFI\Microsoft\Boot\bootmgfw.efi
    │
    ├───Dell
    │   ├───Bios
    │   │   └───Recovery
    │   │           BIOS_BIR.RCV
    │   │           BIOS_PRE.rcv
    │   │           BIOS_CUR.RCV
    │   │
    │   └───logs
    │           diags_previous.xml
    │           diags_current.xml
    │
    ├───GRUB
    │       grubx64.efi
    │
    └───debian
            shimx64.efi
            grubx64.efi
            mmx64.efi
            fbx64.efi
            BOOTX64.CSV
            grub.cfg

Misc

The paritition type UUID («GPT GUID») for an EFI System Partition is c12a7328-f81f-11d2-ba4b-00a0c93ec93b.

See also

partition
On Windows, the EFI System Partition can be mounted with mountvol … /s

Wikipedia Link

Index

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