I tested the command on my dm900 and resized the rootfs partition twice: 1GB -> 2GB -> 1GB
The Box is still alive and the partition table and sizes are the same as before the flash expansion.
That is great to know, thanks again and wise of you not to post the command line before it's been tested. I also searched extensively before asking about the command so I was pretty confident it could’t be found anywhere on the internet Too bad important information like this got lost with the closing of the OoZooN board. This time I will store the command line locally (fingers crossed the Newnigma2 board and the Merlin Board which is presently being reorganised will remain available for many years to come ) if I ever need to repartition again.