EFI System Partition
also: ESP, EFI Boot Partition, UEFI System Partition
A small, FAT32-formatted partition required on UEFI systems that stores bootloader files and firmware configuration, analogous to the MBR in BIOS-based systems.
The EFI System Partition (ESP) is a dedicated partition present on all UEFI-based computers that contains the bootloader, kernel images, and other files needed for the system to boot. It is formatted with FAT32 to ensure compatibility with UEFI firmware, which has built-in FAT32 support.
On a typical Linux system, the ESP is mounted at /boot/efi and contains a directory structure like /EFI/BOOT/ or /EFI/ubuntu/ (depending on the distribution) where files such as grubx64.efi or shimx64.efi are stored. The partition is usually 100–512 MB in size.
When you install Linux on a UEFI system, the installer typically creates or reuses an existing ESP. The bootloader (like GRUB2 or systemd-boot) reads the kernel and initial ramdisk from this partition and passes control to the kernel to continue the boot process.