If a segment with the NOHDR attribute set becomes the first loadable segment in the output object, the ELF and program headers will not be included within the segment.
The NOHDR attribute differs from the top level HDR_NOALLOC directive in that HDR_NOALLOC is a per-segment value, and only has an effect if the segment becomes the first loadable segment. This feature exists primarily to provide feature parity with the older mapfiles. See Appendix E, System V Release 4 (Version 1) Mapfiles for more details.
The HDR_NOALLOC directive is recommended in preference to the segment NOHDR attribute.