The Arduino YUN shield is a shield that combines an additional stand alone processor and WIFI. It runs a cut down Linux distro called OpenWRT. This WIFI / OpenWRT setup is most often found in things like Wifi routers. Arduino originally combined this with a Duemilanove on a single board to make the Arduino YUN, but the good folks at Geeetech and Dragon split the YUN interface out onto a seperate Arduino shield so that it could be used with a variety of different Arduino boards. The cool thing about these setups is that the Linux side of the package can talk to the Arduino side, which not only means that you have effectively given your Arduino WIFI capabilities but also makes it very easy to make IOT devices that need things like WIFI / Web interface / External Logging / Network Logging, well you get the idea, the list goes on. It's truly a very powerful tool.

If you want to use the YUN to install additional programs or datalog you will need to expand the existing memory as it is woefully small. You can do this using an external USB drive

First I decided to update the firmware to a more recent version. The Geeeetech Iduino Yun shield that I have was relatively old (Although when I bought it, it had just come out) and I could not find any firmware update files for it available from Geeetech. The Iduino seems to be based on the Dragino Yun shield, but the hardware did not appear to exactly match any of the Dragino versions. I was therefore hesitant to use any of the Dragino firmware files. The same applied to the Arduino YUN firmware. Whilst the Geeetech and Dragon Shields both use the Arduino firmware, they also implement additional code to cater for a variety of boards (the Arduino Yun is effectively an all-in-one based on the arduino duemilanove), so I decided not to try just in case i bricked the device. So my first step - upgrading the firmware to a current version, basically failed at the first hurdle. (NOTE: the arduino firmware uses different pins and is not compatible)

Connecting to the Geeetech Iduino YUN

A basic overview of the iduino-YUN shield is available on the Geeetech WIKI which covers initial set up and connect in more detail, but for a quick and dirty step-by-step follow these steps...

Reset iduino by holding button for over 30 secs

Connect to iduino ad-hoc network by wireless ( it will create a WIFI network you can connect to) 

Now navigate to the device in your browser NOTE - Default IP address of the YUN Shield is

Log in - the default password - iduino


Updating the firmware

Next - If like me you have an older version you will need to update the firmware (Later Dragino IOT firmware will also work but there are some caveats) you can skip this step if you don't need to update.

Go to: 

Download the relevant sysupdate file (I used Version 4.1.2)

Go to Admin interface in browser - System > System > Firmware update

Select the file you just downloaded and update the firmware - Uncheck the box to 'keep settings'

Once the unit has updated and rebooted it will create a different ad-hoc WIFI network (remember we've just re-flashed the firmware so our previous settings are not available)

Join Dragino-A84041140790 wireless net (or whatever the dragino WIFI net that's just been created is called)

browse to

log in - password is dragino


Configure the wireless network

Go to System > Wireless parameters

Add your local wifi details and then press 'configure / restart'

Then rejoin your local wifi net on your computer

Now you should be able to connect to iduino by IP in your browser - you will need to check with your router what ip address has been assigned to the iduino, it will most likely be something like - 192.168.x.x 

You should also now be able to connect via SSH to 192.168.x.x:22 using your favourite SSH client. The username / password is: root / iduino You will need to use SSH for the following steps.


Using an external USB / SD Card to increase memory.

If you want to use your YUN for anything worthwhile you will likely want to install other software on it or have some room to store stuff so the first thin that you need to address is the lack of storage space. This is easily done by utilising some form of external drive.

Newer versions of the YUN shield come with an SD slot. The version I have only has a USB port. The Arduino YUNs also have an SD slot. The following should work for any board with access to either an SD or USB port as it essentially does not care where the devices are located, they are just referenced as mount points.

First, lets see what we have to start with...

In your browser, go to the Iduino and navigate to System > Advanced configuration > System > Mountpoints to view existing partitions and mount points along with space used. It will show you what existing filesystems are mounted and their sizes



Setting up the USB  

I used a Sandisk 32gb USB 3.0 memory stick simply as it was physically the smallest I could find. You could also use an external hard drive or anything else that suited your project.

We'll be formatting the drive and then telling the Yun to use it instead of the internal memory, which will give us heaps of space to install additional programs and save data.

Now is the time to plug it in.


First we need to update the packages list. Issue the following command via your SSH client

opkg update


Next install the utilities to format in EXT4 (note these packages were appropriate for my older YUN shield, they should also work for later versions but are untested)

opkg install e2fsprogs mkdosfs fdisk rsync


Next clear the partition table

dd if=/dev/zero of=/dev/sda bs=4096 count=10


Create the data partition - this is allocated 1024Meg (1 Gb) This is available to the Arduino and so must be formatted as FAT (which we will do in a sec)

(echo n; echo p; echo 1; echo; echo +1024M; echo t; echo c; echo w) | fdisk /dev/sda


Create the swap partition (1024 Meg) NOTE: system RAM is only 64Meg so you may need to assign more swap depending on your intended use.

(echo n; echo p; echo 2; echo; echo +1024M; echo t; echo 2; echo 82; echo w) | fdisk /dev/sda


Create the linux partition (remaining space)

(echo n; echo p; echo 3; echo; echo; echo w) | fdisk /dev/sda


Next format the data partition to FAT32

mkfs.vfat /dev/sda1


Format the swap partition

mkswap /dev/sda2


and format the linux partition to Linux EXT4

mkfs.ext4 /dev/sda3


Now we have the relevant partitions we need to copy the existing data from the device onto the USB stick 

We start with creating the Arduino folder structure

mkdir -p /mnt/sda1

mount /dev/sda1 /mnt/sda1

mkdir -p /mnt/sda1/arduino/www


Next we copy the files from Arduino Yun flash to the USB

mkdir -p /mnt/sda3

mount /dev/sda3 /mnt/sda3 

rsync -av  --exclude=/mnt/ --exclude=/www/sd /overlay/ /mnt/sda3/



Setting up FSTAB

So up until now we've formatted and partitioned the USB and we've copied the filesystem from the YUN into the Linux partition we created. Next we need to change which filesystem mount-points the device uses when it boots up. We want it to use our newly created USB partitions as our 'external root' or 'extroot' as it is referred to on the OpenWrt project page.  To do this the /etc/config/fstab file needs to be modified so that the appropriate mount points are used on boot. you can use the command...

block detect > /etc/config/fstab 

you will need to edit the file with vim:

vim /etc/config/fstab

Or if like me you prefer nano you can install it with the following command

opkg update && opkg install nano


I needed to change the targets to /data and /overlay extend delay_root and also enable each option...


config 'global' option anon_swap '0' option anon_mount '0' option auto_swap '1' option auto_mount '1' option delay_root '35' option check_fs '0' config 'mount' option target '/data' option uuid 'CD16-9E2C' option enabled '1' config 'swap' option device '/dev/sda2' option enabled '1' config 'mount' option target '/overlay' option uuid 'a48cb511-2aca-4bcc-bbab-fd872383239e' option enabled '1'


Next we need to enable fstab at boot

/etc/init.d/fstab enable


 then reboot by issuing the following command



Wait until the WIFI LED on the board is flashing to indicate that it has rejoined the WIFI network and rejoin your SSH & browser sessions

Check the mounted filesystems - either in the admin interface System > Mount Points or on the command line using the df command...


root@dragino-140790:~# df
Filesystem 1K-blocks Used Available Use% Mounted on rootfs 29184600 565376 27156392 2% / /dev/root 8960 8960 0 100% /rom tmpfs 30560 636 29924 2% /tmp tmpfs 512 0 512 0% /dev /dev/sda3 29184600 565376 27156392 2% /overlay overlayfs:/overlay 29184600 565376 27156392 2% / /dev/sda1 511720 16 511704 0% /data

As you can see both overlay and rootfs are now the size of the linux partition we created earlier

TIP: Before we go any further it's worth checking that the swap is actually enabled in the Dragon admin panel under System > Mount Points, without the swap enabled file actions will be a LOT slower as the unit only has limited ram, in fact installation of larger apps will likely fail.

Congrats, now you have some room to use. Now we can start to install other stuff.