Troubleshooting Reinstall Duo

Location of the FEL button on the MOD Duo

Different MOD Duo models
LEFT: older model with nand flash; RIGHT: newer model with eMMC

Troubleshooting section dedicated to the MOD Duo.

Please note that there are 2 different kinds of MOD Duo units - older ones with nand flash and newer ones with eMMC.
The new unit models have their name (like "MOD Duo") written and engraved above the right display.
Knowing which type of unit you have is important as the re-installation/reset procedure is not the same for each one.
(MOD Duo X units are always of the newer eMMC type)

For older Duo models:
You can first try to reinstall the bootloader, which will keep all data intact, but if the issue is somewhere else the MOD will continue to not boot.
This is the best option, if it works. (and applies to your unit, of course)
If that does not work, you can perform a factory reset, which will erase all your data.

For all Duo models:
You can reinstalling the OS over USB, optionally formatting/reset the user data partition as well.
This method only works on Linux at the moment.

Reinstall bootloader

NOTE: Only for older MOD Duo units with nand flash

Requirements: Linux or macOS, basic command-line knowledge

To begin:

1. Click and hold down the FEL button on the back of the MOD Duo (in tiny hole), while you power it on.
2. Hold it for 2 seconds, then release (The screens will freeze with the MOD logo and name)
3. Connect the MOD Duo to your computer via USB cable
4. Download https://github.com/moddevices/CT_NandBoot/archive/master.zip and extract it
5. Open a terminal and 'cd' to the directory where master.zip was extracted, ie:

cd ~/Downloads/CT_NandBoot-master/

If you're running macOS, run:
./bootfix.osx

If you're running Linux 64bit, run:
./bootfix
(sudo will likely be needed here)

For non-64bit Linux systems, run 'make clean' and 'make' beforehand.

After the command finishes running, just power the MOD off and on again.
If it still doesn't boot after 2 minutes, a factory reset or OS reinstall via USB is needed.

MOD Duo Factory Reset

NOTE: Only for older MOD Duo units with nand flash

Requirements: Linux or macOS, basic command-line knowledge
For a factory reset under Windows, see Troubleshooting_Reinstall_via_LiveSuit. (applies only to older MOD Duo units with nand flash)

To begin:

1. Click and hold down the FEL button on the back of the MOD Duo (in tiny hole), while you power it on.
2. Hold it for 2 seconds, then release (The screens will freeze with the MOD logo and name)
3. Connect the MOD Duo to your computer via USB cable
4. Download this file: http://download.moddevices.com/releases/modduo/reset/modduo-latest-reset-image.raw
5. Download https://github.com/moddevices/CT_NandBoot/archive/master.zip and extract it
6. Open a terminal and 'cd' to the directory where master.zip was extracted, ie:

cd ~/Downloads/CT_NandBoot-master/

If you're running macOS, run:
./bootfix.osx -w ~/Downloads/modduo-latest-reset-image.raw
(adjust the path to 'modduo-latest-reset-image.raw' as needed)

If you're running Linux 64bit, run:
./bootfix -w ~/Downloads/modduo-latest-reset-image.raw
(adjust the path to 'modduo-latest-reset-image.raw' as needed, sudo will likely be needed here)

For non-64bit Linux systems, run 'make clean' and 'make' beforehand.

Continuing:

1. Wait until the 'bootfix' process finishes
2. Power off and on the MOD Duo (by replugging the power cable)
3. Wait until its LEDs turn blue, after around 30 seconds. If the LEDs don't light up after one minute, replug the power cable once again
4. Wait until the LEDs turn red, then green. This should take around 10 minutes.

Once the LEDs are green, the MOD Duo has finished its factory reset.
Power it off and on again one last time, and it will be good as new :)

If the LEDs are still blue for too long (actually they go to red and then return to blue) or the display shows the message "copy file, eject and unplug", please execute all this process again starting from the bootfix command.

Reinstall via USB boot

Requirements: Linux, basic command-line usage

To begin:

1. Click and hold down the FEL button on the back of the MOD Duo (in tiny hole), while you power it on.
2. Hold it for 2 seconds, then release (The screens will freeze with the MOD logo and name)
3. Connect the MOD Duo to your computer via USB cable
4. Download http://download.moddevices.com/releases/modduo/tools/mod-boot-fel-restore-v2.tar.gz and extract it
5. Open a terminal and 'cd' to the directory where mod-boot-fel-restore.zip was extracted, ie:

cd ~/Downloads/mod-boot-fel-restore/

If not you're running 64bit, install sunxi-tools from your Linux distribution, and copy /usr/bin/sunxi-fel to the current directory, overriding the existing file there.

Continuing, we will run a command with different environment variables depending on the target unit.

For the new MOD Duo units with eMMC, run:
EMMC=1 ./boot-fel-restore.sh

For non-kickstarter units, run:
MARS=1 ./boot-fel-restore.sh

For kickstarter units, run:
./boot-fel-restore.sh

(NOTE: it might be possible that kickstarter units have the "MARS" model, and a non-kickstarter one not.
It is not possible to tell which kinda unit it is just by looking at it externally, so if the command with "MARS" does not work for you, try the one without and vice-versa.)

1. After the script finishes, wait for around 2 minutes and the MOD Duo will boot into recovery mode.
2. Install a MOD OS release as usual.

Note: You can find all MOD OS software releases in the Releases section.