[Solved] RasPiKey: no disk space / readonly / can not write file

RasPiKey was provision with a compressed disk image, which may not use all disk space (16GB/32GB) in RasPiKey. You can expand the file system to use all space available.

You can do it with raspi-config:

sudo raspi-config

Enter the "Advanced Options", and choose "Expand Filesystem". Confirm your selection and wait. You will soon see the "Root partition has been resized" message. After rebooting, the file system is expanded and no space is wasted.