To install to the internal eMMC plug your SD into your PC’s SD card reader…
Make sure the card is not mounted, mine shows up as “sdc” so i do the following:
sudo umount /dev/sdc1
sudo umount /dev/sdc2
Write the image to SD:
xzcat ubuntu-core-16-nanopi-air.img.xz | sudo dd of=/dev/sdc bs=32M
Attach the serial cable to the board and fire up screen:
sceen /dev/ttyUSB0 115200
Put the card in the board, attach the antenna, apply power and run through the configuration wizard.
Remove power and plug the SD back into your PC, wait til it auto-mounts (or mount it manually if you have this turned off on your desktop)
cp ubuntu-core-16-nanopi-air.img.xz /media/<user>/writable/user-data/<user>/
Unmount the SD and plug it back into the board … boot it.
Log in with the ssh credentials you received when doing the first configuiration:
xzcat ubuntu-core-16-nanopi-air.img.xz | sudo dd of=/dev/mmcblk1 bs=16M
Shut down the board and remove the card … now boot again and it will boot to eMMC and run the configuration from scratch for the internal install.