Saturday, 25 July 2015

pcDuino3 - using 32GB SD Card as main drive - by Ross Devitt

The pcDuino3B has 1GB Flash memory and 4GB RAM.  With the pcDuino's version of lubuntu installed there's about 1.5GB of free spance for the home partition for user files.  This rapidly shrinks as it fills up with cacheed stuff, especially if you run a browser.

Luckily it is easy to write a shell script to clear the cache regularly and I am playing around with ways to do this at boot.  In the mean time it is a nuisance that such a great and versatile little computer is hamstrung by this lack of usable space.

Ok, first the good news!  According to these instructions on the Linksprite website it is possible to expand the usefuless of the pcDuino3 by cloning the OS to a 32GB micro SD card.

Now the bad news.

It is bullshit.  It might work for some people, but it doesn't work.


I'll put any updates here close to the top of the post so they can be found easily.  
I have jsut tried a third method to create a bootable 32GB microSD.  I used a utility called unetbootin, which usually works with almost anything.  It found the pcDuino .img file, and it even wrote it to the card.  But no way was it interested in booting.

Ok, back to the original post:
By following the steps exactly as written, I managed to end up with a 32GB microSD card with a dead partiton table.  It would not show up on any computer.  So I tried a 16GB card and ended up with a dead microSD card.  After that I wondered if I had a couple of dud cards, so I bought a brand new Sandisk Ultra microSD card and tried that.

Sure enough after carefully following the steps exactly I had another dead card.  Luckily Gparted on my Linux computer enabled me to rebuild the cards, Testing each one as I finished to make sure I could write a file to it and delete the file again.

Tried the thing again and managed to get one card that went through the motions of booting, but locked in a loop that asked for a sh file it expected to find on a USB disk. However reading the file told me it would overwrite the on-board nand and that is not somethign I wasnte to do accidentally.

I found another site that offered a more traditional way to burn a bootable 32GB micro SD using the following method.

sudo dd if=/home/user/file.img of=/dev/sdX bs=1M
     FIRST - UNMOUNT sdb1
     umount /dev/sdb1
     THEN - write the image
Wonderful!  I now had about 8MB of my 32GB disk used.  But still not bootable.

A bit of googling suggests this is a pretty common problem and nobody has devised a solution to it yet.  My guess is that there is somethign missing from the instructions at

My advice - forget about trying to use a 32GB card if it doesn;t work the first time and if you are worried aboout destroying partitions on the microSD cards.

However all is not lost.  Although I was not able to fix the lack of storage, I was able to delete some cache files and fix one other problem - which will be addressed in the following post.

And I am still trying to find a solution to the bootable 32GB micro SD problem.  If I could only find the thing as an iso instead of an img file.

Cheers,  RossD.

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