EFISystempartitionOrdner

The EFI System Partition (ESP) is a special partition used by UEFI firmware to locate and load bootloaders and related boot-time utilities. It resides on GPT disks and is required for systems that boot in UEFI mode. The ESP is typically formatted as FAT32 and marked with the boot and esp attributes. Its size is generally small, commonly around 100 to 300 MB, though larger ESPs may be used for multiple operating systems.

Contents and structure: The ESP stores EFI executables organized in subdirectories under the path /EFI. Windows installations place bootloaders such as Bootmgfw.efi in /EFI/Microsoft/Boot, along with the BCD data file. Linux distributions place their bootloaders under /EFI/{Distribution}, for example /EFI/ubuntu, and include components like shim.efi and grubx64.efi. A fallback loader such as /EFI/Boot/bootx64.efi can be used if a specific loader is unavailable. Different operating systems can share the same ESP in multiboot configurations.

UEFI boot process and usage: On UEFI systems, the firmware loads an EFI executable from the ESP to start the OS boot process. The firmware maintains a boot order that can be configured in the UEFI setup or by boot managers. In dual-boot environments, multiple bootloaders may reside on a single ESP, with the active bootloader selecting the appropriate OS.

Management and cautions: The ESP is essential for booting; altering or deleting bootloader files can render a system unbootable. It is common to mount the ESP for maintenance (for example, to update bootloaders) but should be done carefully, and backups are advisable before major changes.