This is using Android 4.2 Bootable SD image for pcDuino3.
I used dd in Ubuntu to write to the 32GB card in usb card-reader in PC.
Put the SD card into the pcDuino, apply power and wait for the installation to complete.
Choose your language, time, zone, etc and get wi-fi/ethernet working in Settings. Make sure all is working ok.
Shutdown, remove power and remove SD card.
Put the SD card back in the card-reader and launch Gparted.
I have to assume you know how to move/resize partitions in Gparted.
The partitions shown will be as in 1st attachment.
You will see that there is only 256MiB for the “SD card storage” in the fat16 partition
and 1024MiB (512 + 512) for the system/data partitions.
In your file manager, copy the contents of the fat16 volume to a temporary folder on your hard drive, ensure you are showing hidden folders, see the 2nd attachment.
Using Gparted, format all the “unknown” partitions to ext4, keeping the same size. This is necessary to be able to move/resize other partitions.
Move and resize the partitions to achieve that shown in 3rd attachment. Note that the fat partition needs to be recreated as a fat32 partition, because of the 2GiB (4GiB?) restriction on fat16.
I resized the 512MiB ext4 partitions to 4GiB each, keeping all other ext4 partitions the original size.
Lastly, paste the original fat16 contents back into the fat32 volume.
Return the SD card to the pcDuino, switch on. In Settings -> Storage you should see about 4GB in “Internal Storage” and 21GB in “SDcard”. Enjoy.
Note: quite handy to know that if you remove the SD card, the pcDuino will boot back into the prior NAND image, which in my case is the original shipped Lubuntu.