grubx64efi

grubx64.efi is the 64-bit UEFI executable of the GNU GRUB bootloader for x86_64 systems. It is the primary bootloader binary used on many Linux distributions when booting in UEFI mode. The file is an EFI application that the UEFI firmware loads from the EFI System Partition during system startup.

Functionality and role: grubx64.efi provides a boot menu, reads configuration data from grub.cfg or via its command line, loads modules, and loads the chosen kernel with its parameters and initial RAM disk. It can boot multiple operating systems, chainload other bootloaders, and support custom boot entries. Its behavior is driven by the GRUB configuration and the available modules.

Architecture and capabilities: As part of GNU GRUB, grubx64.efi uses a modular architecture. The set of features available to a given binary depends on the compiled modules, including filesystem drivers, device handling, network support, cryptsetup/LUKS, and various boot methods. It supports a wide range of filesystems commonly used on Linux and other OSes, such as ext2/3/4, btrfs, XFS, NTFS, and VFAT, among others.

Secure boot and compatibility: In Secure Boot environments, grubx64.efi is typically loaded through a signed chain that may involve a shim, and keys can be enrolled to authorize GRUB. Proper signing and key management are required for the boot process to proceed on Secure Boot systems.

Installation and file locations: grubx64.efi is installed by distribution tools such as grub-install and placed on the EFI System Partition. Typical locations include EFI/GRUB/grubx64.efi or EFI/BOOT/bootx64.efi, with boot entries registered in the firmware. A fallback copy may exist to support various firmware implementations.

Licensing and development: grubx64.efi is maintained as part of the GNU GRUB project and released under the GNU General Public License. Development is active and community-driven, with contributions from volunteers and major Linux distribution maintainers.