I have worked out the dd command to copy my work in progress 4Gb image: dd if=/dev/sdb of=cubietruck.img bs=512 count=6268927 and restore it with: dd if=/home/rgm/arm/Centos/cubietruck.img of=/dev/sdb bs=4M; sync But I would like to compress this, making a .xz file that is expanded with xzcat. I have not figured this out, so am asking for a bit of help (I have had to increase the root partition so backing up is a larger file now). thanks