Update README.md

README.md

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 # radxa-rock-lite-ubuntu
 Build Ubuntu SD card image for Radxa Rock Lite
+
+Based on the following links:
+
+* https://wiki.radxa.com/Rock/Linux_Mainline
+* https://wiki.radxa.com/Rock/U-Boot#For_SD_card
+* https://wiki.radxa.com/Rock/make_sd_image
+
+Kernel version: 4.4.221
+Ubuntu version: latest 16.04
+
+## Build
+
+`./build.sh`
+
+This will build 3 files:
+
+* u-boot-sd.img
+* parameter.im
+* boot.img
+
+## Root FS
+
+* https://github.com/sgjava/ubuntu-mini#create-ubuntu-root-filesystem-mk808-mk802iv-etc
+
+## Prepare SD card and flash
+```
+dd if=/dev/zero of=/dev/disk/by-id/YOURDISK bs=1M count=1
+export START_SECTOR=131072
+
+fdisk /dev/disk/by-id/YOURDISK  << EOF
+n
+p
+1
+$START_SECTOR
+
+w
+EOF
+
+dd if=u-boot-sd.img of=/dev/disk/by-id/YOURDISK conv=sync seek=64 
+dd if=parameter.img of=/dev/disk/by-id/YOURDISK conv=sync seek=$((0x2000))
+dd if=boot.img of=/dev/disk/by-id/YOURDISK conv=sync seek=$((0x2000+0x2000))
+dd if=rootfs.ext4 of=/dev/disk/by-id/YOURDISK-part1 conv=sync
+```