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.

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

• 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.