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Topic: Dragino Yun Shield - Expand Disk Space with USB - Solution + Tutorial (Read 417 times) previous topic - next topic


i just managed to expand the Disk Space of the Dragino Yund Shield (which comes without SD-Card!), using a standart USB-Stick and a Arduino Mega 2560.

What i did:

1) Remove the jumper, to get the Arduino out of reset mode:

2) Include in the Sketch YunDiskExpander "#include <Console.h>"

3) Change the Setup:
Code: [Select]

  while (!Console);

4) Replace in the Sketch YunDiskExpander "Serial" with "Console", don´t change "Serial1"


Copy my the Code of the next post:

5) Upload the Sketch using Arduino IDE, your Board connected via USB and selected as without shield (Exaple: Mega 2560 on Com 3)

6)Reconnect the jumper on the Arduino Board:

7) Connect Arduino to power source by DC Plug.

8.) In Arduino IDE select YunShield with WiFi connection (Example Yun SHield on

9) Open Serial Monitor, make sure BaudRate in 115200 an NewLine selected.

10) IMPORTANT: The questions from Arduino as in the original tutorial wont be asked (Example "Do you wish to proceed")!

So follow the totorial blind
Original Tutorial

11) When ready wait min. 15 Seconds to avoid errors, then reconnect power source and wait to boot up.

12) enjoy you powerfull extendet Yun Shield!

 :smiley-cool: Have fun!  :smiley-cool:

Code: [Select]

   Yún Shield Disk Space Expander
  * Arduino Board
  * Dragino Yun Shield
  * USB Stick
  * internet connection

  This sketch configure the USB Stick to expand the disk space
  of the Yún Shield. Upload, open the Console Monitor and follow
  the interactive procedure.

  Warning: your USB Stick will be formatted and you will lose
  the files it contains. Be sure you have backed it up before
  using it for expanding Yún's Shield disk space.
  created Apr 2014
  by Federico Fissore & Federico Vanzati
 >> modded by HandyFreak Okt 2014 for DraginoYun Shield

  This code without any responsibility of damages or errors, successfully tested by me with Mega 2560.

#include <Process.h>
#include <Console.h>   //Console class provide the interactive between IDE and Yun Shield

#define DEBUG 0

void setup() {
  while (!Console);

  Console.print(F("This sketch will format your USB Stick and use it as additional disk space for your Arduino Yun.\nPlease ensure you have ONLY one USB-Stick plugged in: no other drives, hard drives or whatever.\nDo you wish to proceed (yes/no)?"));

  Console.println(F("\nStarting Bridge..."));








  Console.print(F("\nWe are done! Yeah! Now reconnect to power to apply the changes."));

void loop() {
  // This turns the sketch into a YunSerialTerminal
  if (Console.available()) {
    char c = (char)Console.read();
  if (Serial1.available()) {
    char c = (char)Serial1.read();

void halt() {
  while (true);

void expectYesBeforeProceeding() {

  while (!Console.available());

  String answer = Console.readStringUntil('\n');

  Console.print(F(" "));
  if (answer != "yes") {

int readPartitionSize() {
  int partitionSize = 0;
  while (!partitionSize)
    Console.print(F("Enter the size of the data partition in MB: "));
    while (Console.available() == 0);

    String answer = Console.readStringUntil('\n');
    partitionSize = answer.toInt();
    if (!partitionSize)
      Console.println(F("Invalid input, retry"));
  return partitionSize;

void debugProcess(Process p) {
  #if DEBUG == 1
  while (p.running());

  while (p.available() > 0) {
    char c = p.read();

void haltIfSDAlreadyOnOverlay() {
  Process grep;

  grep.runShellCommand(F("mount | grep ^/dev/sda | grep 'on /overlay'"));
  String output = grep.readString();
  if (output != "") {
    Console.println(F("\nMicro SD card is already used as additional Arduino Yun disk space. Nothing to do."));

void haltIfSDCardIsNotPresent() {
  Process ls;
  int exitCode = ls.runShellCommand("ls /mnt/sda1");

  if (exitCode != 0) {
    Console.println(F("\nThe USB Stick is not available"));

void haltIfInternalFlashIsFull() {
  Process awk;

  awk.runShellCommand(F("df / | awk '/rootfs/ {print $4}'"));
  int output = awk.parseInt();
  if (output < 1000) {
    Console.println(F("\nYou don't have enough disk space to install the utility software. You need to free at least 1MB of Flash memory.\nRetry!"));

void installSoftware() {
  Console.print(F("\nReady to install utility software. Please ensure your Arduino Yun is connected to internet.\nReady to proceed (yes/no)?"));

  Console.println(F("Updating software list..."));

  Process opkg;

  // update the packages list
  int exitCode = opkg.runShellCommand("opkg update");
  // if the exitCode of the process is OK the package has been installed correctly
  if (exitCode != SUCCESSFUL_EXIT_CODE) {
    Console.println(F("err. with opkg, check internet connection"));
  Console.println(F("Software list updated. Installing software (this will take a while)..."));

  // install the utility to format in EXT4
  exitCode = opkg.runShellCommand(F("opkg install e2fsprogs mkdosfs fdisk rsync"));
  if (exitCode != SUCCESSFUL_EXIT_CODE) {
    Console.println(F("err. installing e2fsprogs mkdosfs fdisk"));
  Console.println(F("e2fsprogs mkdosfs fdisk rsync installed"));

void partitionAndFormatSDCard() {
  Console.print(F("\nProceed with partitioning USB Stick (yes/no)?"));


  Process format;

  //clears partition table
  format.runShellCommand("dd if=/dev/zero of=/dev/sda bs=4096 count=10");

  // create the first partition
  int dataPartitionSize = readPartitionSize();

  Console.println(F("Partitioning (this will take a while)..."));
  String firstPartition = "(echo n; echo p; echo 1; echo; echo +";
  firstPartition += dataPartitionSize;
  firstPartition += "M; echo w) | fdisk /dev/sda";


  // create the second partition
  format.runShellCommand(F("(echo n; echo p; echo 2; echo; echo; echo w) | fdisk /dev/sda"));


  // specify first partition is FAT32
  format.runShellCommand(F("(echo t; echo 1; echo c; echo w) | fdisk /dev/sda"));




  // format the first partition to FAT32
  int exitCode = format.runShellCommand(F("mkfs.vfat /dev/sda1"));
  if (exitCode != SUCCESSFUL_EXIT_CODE) {
    Console.println(F("\nerr. formatting to FAT32"));

  // format the second partition to Linux EXT4
  exitCode = format.runShellCommand(F("mkfs.ext4 /dev/sda2"));
  if (exitCode != SUCCESSFUL_EXIT_CODE) {
    Console.println(F("\nerr. formatting to EXT4"));

  Console.println(F("USB Stick correctly partitioned"));

void createArduinoFolder() {
  Console.print(F("\nCreating 'arduino' folder structure..."));
  Process folder;

  folder.runShellCommand(F("mkdir -p /mnt/sda1"));
  folder.runShellCommand(F("mount /dev/sda1 /mnt/sda1"));
  folder.runShellCommand(F("mkdir -p /mnt/sda1/arduino/www"));


void copySystemFilesFromYunToSD() {
  Console.print(F("\nCopying files from Arduino Yun flash to USB Stick..."));
  Process copy;

  copy.runShellCommand(F("mkdir -p /mnt/sda2"));
  copy.runShellCommand(F("mount /dev/sda2 /mnt/sda2"));
  copy.runShellCommand(F("rsync -a --exclude=/mnt/ --exclude=/www/sd /overlay/ /mnt/sda2/"));


void unmount() {
  Process format;
  format.runShellCommand(F("umount /dev/sda?"));
  format.runShellCommand(F("rm -rf /mnt/sda?"));

void enableExtRoot() {
  Console.print(F("\nEnabling USB Stick as additional disk space... "));

  Process fstab;

  fstab.runShellCommand(F("uci add fstab mount"));
  fstab.runShellCommand(F("uci set fstab.@mount[0].target=/overlay"));
  fstab.runShellCommand(F("uci set fstab.@mount[0].device=/dev/sda2"));
  fstab.runShellCommand(F("uci set fstab.@mount[0].fstype=ext4"));
  fstab.runShellCommand(F("uci set fstab.@mount[0].enabled=1"));
  fstab.runShellCommand(F("uci set fstab.@mount[0].enabled_fsck=0"));
  fstab.runShellCommand(F("uci set fstab.@mount[0].options=rw,sync,noatime,nodiratime"));
  fstab.runShellCommand(F("uci commit"));



I tried this with the Dragino Yun shield that I have.  It did not work correctly.  The partitions were created and the files copied.  However, upon the restart, the flash drive was not mounted.   It appears the flash drive (/dev/sda) was not detected and mounted.   I have the latest version of the Dragino OpenWrt.  I am using version Dragino-V2 common-1.3.5 of OpenWrt.   I suspect the problem is related to the version.

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