GitHub - maharmstone/ntfs2btrfs
Probably need to not care too much about your data :)
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.
github.com/maharmstone/ntfs2bt…GitHub - maharmstone/ntfs2btrfs
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