// Best effort at populating Devmajor and Devminor.
	if h.Typeflag == TypeChar || h.Typeflag == TypeBlock {
		dev := uint64(sys.Rdev) // May be int32 or uint32
		switch runtime.GOOS {
		case "aix":
			var major, minor uint32
			major = uint32((dev & 0x3fffffff00000000) >> 32)
			minor = uint32((dev & 0x00000000ffffffff) >> 0)
			h.Devmajor, h.Devminor = int64(major), int64(minor)
		case "linux":

//	Uname/Gname       |    32B | unlimited |       32B
//	ModTime           | uint33 | unlimited |     int89
//	AccessTime        |    n/a | unlimited |     int89
//	ChangeTime        |    n/a | unlimited |     int89
//	Devmajor/Devminor | uint21 |    uint21 |    uint57
//	------------------+--------+-----------+----------
//	string encoding   |  ASCII |     UTF-8 |    binary
//	sub-second times  |     no |       yes |        no

	fmtNum(v7.modTime(), modTime.Unix())

	ustar := tw.blk.toUSTAR()
	fmtStr(ustar.userName(), hdr.Uname)
	fmtStr(ustar.groupName(), hdr.Gname)
	fmtNum(ustar.devMajor(), hdr.Devmajor)
	fmtNum(ustar.devMinor(), hdr.Devminor)

	return &tw.blk
}

// writeRawFile writes a minimal file with the given name and flag type.
// It uses format to encode the header format and will write data as the body.

	if format > formatV7 {
		ustar := tr.blk.toUSTAR()
		hdr.Uname = p.parseString(ustar.userName())
		hdr.Gname = p.parseString(ustar.groupName())
		hdr.Devmajor = p.parseNumeric(ustar.devMajor())
		hdr.Devminor = p.parseNumeric(ustar.devMinor())

		var prefix string
		switch {
		case format.has(FormatUSTAR | FormatPAX):
			hdr.Format = format
			ustar := tr.blk.toUSTAR()
			prefix = p.parseString(ustar.prefix())