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EFI FileSystem drivers
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EfiFs - EFI File System Drivers

This is a GPLv3+ implementation of standalone EFI File System drivers, based on the GRUB 2.0 read-only drivers.

For additional info as well as precompiled drivers, see


  • Visual Studio 2019 (Windows) MinGW (Windows), gcc (Linux) or EDK2.
  • A git client able to initialize/update submodules
  • QEMU v2.7 or later if debugging with Visual Studio (NB: You can find QEMU Windows binaries here)



  • Fetch the git submodules with git submodule init and git submodule update.
    NOTE This only works if you cloned the directory using git.
  • Apply 0001-GRUB-fixes.patch to the grub\ subdirectory. This applies the changes that are required for successful compilation of GRUB.

Visual Studio (non EDK2)

  • Open the solution file and hit F5 to compile and debug the default driver.

gcc (non EDK2)

  • Run make in the top directory. If needed you can also issue something like make ARCH=<arch> CROSS_COMPILE=<tuple> where <arch> is one of ia32, x64, arm or aa64 (the official UEFI abbreviations for an arch, as used in /efi/boot/boot[ARCH].efi) and <tuple> is the one for your cross- compiler, such as arm-linux-gnueabihf-. e.g. make ARCH=aa64 CROSS_COMPILE=aarch64-linux-gnu-


  • Open an elevated command prompt and create a symbolic link called EfiFsPkg, inside your EDK2 directory, to the EfiFs source. On Windows, from an elevated prompt, you could run something like mklink /D EfiFsPkg C:\efifs, and on Linux ln -s ../efifs EfiFsPkg.
  • From a command prompt, set Grub to target the platform you are compiling for by invoking:
    • (Windows) set_grub_cpu.cmd <arch>
    • (Linux) ./ <arch>
      Where <arch> is one of ia32, x64, arm or aarch64.
      Note that you MUST invoke the set_grub_cpu script every time you switch target.
  • After having invoked edksetup.bat (Windows) or (Linux) run something like:
    build -a X64 -b RELEASE -t <toolchain> -p EfiFsPkg/EfiFsPkg.dsc
    where <toolchain> is something like VS2015 (Windows) or GCC5 (Linux).
    NB: To build an individual driver, such as NTFS, you can also use something like:
    build -a X64 -b RELEASE -t <toolchain> -p EfiFsPkg/EfiFsPkg.dsc -m EfiFsPkg/EfiFsPkg/Ntfs.inf
  • Note that, provided that you cloned a recent EDK2 from git, you should be able to use VS2019 as your EDK2 toolchain, including for buidling the ARM or ARM64 drivers, with something like:
    build -a AARCH64 -b RELEASE -t VS2019 -p EfiFsPkg/EfiFsPkg.dsc
  • A Windows script to build the drivers, using EDK2 with VS2019 is also provided as edk2_build_drivers.cmd.


If QEMU is installed, the Visual Studio solution will set up and test the drivers using QEMU (by also downloading a sample image for each target file system). Note however that VS debugging expects a 64-bit version of QEMU to be installed in C:\Program Files\qemu\ (which you can download here). If that is not the case, you should edit .msvc\debug.vbs accordingly.

For testing outside of Visual Studio, make sure you have at least one disk with a target partition using the target filesystem, that is not being handled by other EFI filesystem drivers. Then boot into the EFI shell and run the following:

  • load fs0:\<fs_name>_<arch>.efi or wherever your driver was copied
  • map -r this should make a new fs# available, eg fs2:
  • You should now be able to navigate and access content (in read-only mode)
  • For logging output, set the FS_LOGGING shell variable to 1 or more
  • To unload use the drivers command, then unload with the driver ID

Visual Studio 2019 and ARM/ARM64 support

Please be mindful that, to enable ARM/ARM64 compilation support in Visual Studio 2019, you MUST go to the Individual components screen in the setup application and select the ARM compilers and libraries there, as they do NOT appear in the default Workloads screen:

VS2019 Individual Components

Additional Notes

This is a pure GPLv3+ implementation of EFI drivers. Great care was taken not to use any code from non GPLv3 compatible sources, such as rEFInd's fsw_efi (GPLv2 only) or Intel's FAT driver (requires an extra copyright notice).

Bonus: Commands to compile EfiFs using EDK2 on a vanilla Debian GNU/Linux 10.x

As root:

apt-get install nasm uuid-dev gcc-multilib gcc-aarch64-linux-gnu gcc-arm-linux-gnueabihf
cd /usr/src
git clone
git clone
cd efifs
git submodule update --init
cd grub
patch -Np1 -i ../0001-GRUB-fixes.patch
cd ../../edk2
git submodule update --init
ln -s ../efifs EfiFsPkg
make -C BaseTools
export GCC5_ARM_PREFIX=arm-linux-gnueabihf-
export GCC5_AARCH64_PREFIX=aarch64-linux-gnu-
source --reconfig
./EfiFsPkg/ X64
build -a X64 -b RELEASE -t GCC5 -p EfiFsPkg/EfiFsPkg.dsc
./EfiFsPkg/ IA32
build -a IA32 -b RELEASE -t GCC5 -p EfiFsPkg/EfiFsPkg.dsc
./EfiFsPkg/ AARCH64
build -a AARCH64 -b RELEASE -t GCC5 -p EfiFsPkg/EfiFsPkg.dsc
./EfiFsPkg/ ARM
build -a ARM -b RELEASE -t GCC5 -p EfiFsPkg/EfiFsPkg.dsc
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