Bootable CD - change root dir

Is there a way to change the root directory with sinit -r ? I want to build a rescue cd and all relevant files are stored in the /qnx directory. At the Moment I have a floppy for testing and mount /dev/fd0 as / . But change root ist not so easy.

Have you tried using prefix ?

Yes I have trying prefix, but a booting floppy is a slow medium. Prefix can´t detach /. (resource bussy) etc… I don´t know, is this just as with a CD?

You don’t need to “detach /”, you can just “replace” it:

prefix -R /=/qnx/

Yes this is the problem and was my first action. I have trying this at the begin of the sysinit file. I became this error: prefix: Can´t detach prefix (/) : Resource busy. At the moment trying all on a floppy - for testing. Also I have trying this in the boot image with the same result.