Ntfs2btrfs

Ntfs2btrfs is a tool which does in-place conversion of Microsoft's NTFS filesystem to the open-source filesystem Btrfs, much as btrfs-convert does for ext2. The original image is saved as a reflink copy at image/ntfs.img, and if you want to keep the conversion you can delete this to free up space.

Although I believe this tool to be stable, please note that I take no responsibility if something goes awry!

You're probably also interested in WinBtrfs, which is a Btrfs filesystem driver for Windows.

Thanks to Eric Biggers, who successfully reverse-engineered Windows 10's "WOF compressed data", and whose code I've used here.

Usage

On Windows, from an Administrator command prompt:

ntfs2btrfs.exe D:\

Bear in mind that it won't work with your boot drive or a drive containing a pagefile that's currently in use.

If you are using WinBtrfs, you will need to clear the readonly flag on the image subvolume before you can delete it.

On Linux, as root:

ntfs2btrfs /dev/sda1

Installation

On Windows, go to the Releases page and download the latest Zip file, or use Scoop.

For Linux:

• Arch
• Fedora (thanks to Conan-Kudo)
• Gentoo - available as sys-fs/ntfs2btrfs in the guru repository
• Debian (thanks to alexmyczko)
• Ubuntu (thanks to alexmyczko)
• openSUSE (thanks to David Sterba)

For other distributions or operating systems, you will need to compile it yourself - see below.

Changelog

• 20240115

  • Fixed compilation on GCC 14 (-Werror=incompatible-pointer-types now enabled by default)

• 20230501

  • Fixed inline extent items being written out of order (not diagnosed by btrfs check)
  • Fixed metadata items being written with wrong level value (not diagnosed by btrfs check)
  • ADSes with overly-long names now get skipped

• 20220812

  • Added --no-datasum option, to skip calculating checksums
  • LXSS / WSL metadata is now preserved
  • Fixed lowercase drive letters not being recognized
  • Fixed crash due to iterator invalidation (thanks to nyanpasu64)
  • Fixed corruption when NTFS places file in last megabyte of disk

• 20210923

  • Added (Btrfs) compression support (zlib, lzo, and zstd)
  • Added support for other hash algorithms: xxhash, sha256, and blake2
  • Added support for rolling back to NTFS
  • Added support for NT4-style security descriptors
  • Increased conversion speed for volume with many inodes
  • Fixed bug when fragmented file was in superblock location
  • Fixed buffer overflow when reading security descriptors
  • Fixed bug where filesystems would be corrupted in a way that btrfs check doesn't pick up

• 20210523

  • Improved handling of large compressed files

• 20210402 (source code only release)

  • Fixes for compilation on non-amd64 architectures

• 20210105

  • Added support for NTFS compression
  • Added support for "WOF compressed data"
  • Fixed problems caused by sparse files
  • Miscellaneous bug fixes

• 20201108

  • Improved error handling
  • Added better message if NTFS is corrupted or unclean
  • Better handling of relocations

• 20200330

  • Initial release

Compilation

On Windows, open the source directory in a recent version of MSVC, right-click on CMakeLists.txt, and click Compile.

On Linux:

mkdir build
cd build
cmake ..
make

You'll also need libfmt installed - it should be in your package manager.

Compression support requires zlib, lzo, and/or zstd - again, they will be in your package manager. See also the cmake options WITH_ZLIB, WITH_LZO, and WITH_ZSTD, if you want to disable this.

What works

• Files
• Directories
• Symlinks
• Other reparse points
• Security descriptors
• Alternate data streams
• DOS attributes (hidden, system, etc.)
• Rollback to original NTFS image
• Preservation of LXSS metadata

What doesn't work

• Windows' old extended attributes (you're not using these)
• Large (i.e >16KB) ADSes (you're not using these either)
• Preservation of the case-sensitivity flag
• Unusual cluster sizes (i.e. not 4 KB)
• Encrypted files

Can I boot Windows from Btrfs with this?

Yes, if the stars are right. See Quibble.