Thanks for the link.
I have been using rawrite n+1 times already in the past and so far without problems with writing an image. The images have been for 1.44MB floppy. The howto was no help in this case at first sight.
The \images\cdboot.img in 5.5 ISO is 1440KB and writes fine.
The \dosutils\autoboot\cdboot.img in 6.0u ISO is 2880KB big. There is no \images\cdboot.img.
I see, that the link you gave talks about \images\boot.img so I guess it should be the correct file to look for. I made a mistake assuming, that the image name should be cdboot.img and not just boot.img.
I will try the \images\boot.img on 6.0u ISO that is 1440KB - maybe it works.
Whatfor is the \dosutils\autoboot\cdboot.img? For making a bootable CD?