It is also possible to produce bit-reproducible filesystems with recent mkfs.ext2 from e2fsprogs-1.47.1, thanks to [a SDE patch](https://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git/commit/?id=b6e2913061577ad981464e435026d71a48fd5caf) and added [support for tarball input](https://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git/commit/?id=7e3a4f0a33e9859af2bf44e8e1e278c8b10313cc) that lets tar normalize various metadata.
export SOURCE_DATE_EPOCH=1234
tar --sort=name --mtime=@$SOURCE_DATE_EPOCH --clamp-mtime --pax-option=exthdr.name=%d/PaxHeaders/%f,delete=atime,delete=ctime -cf /tmp/root.tar -C $rootdir .