Convert RetroPie SD Card Image to NOOBS Image

NOOBS (New Out of Box Software) is an easy way to set up an SD card for a Raspberry Pi. It has the added benefit of making it easy to set up the Pi to boot multiple operating systems. Here's how to convert a RetroPie SD Card image to a NOOBS-compatible image.

These instructions are largely based on the instructions for creating a custom OS image on the NOOBS GitHub repository

You will need read access to all partitions of the flashed SD card. While RPi's instructions imply they can be followed directly from the Pi itself, you may be able to find plugins for your primary computer's operating system to allow read access to the ext-formatted partition of the SD card. This will allow you to use the full power of your computer to create the compressed disk image and probably save you hours.

For OS X users, here is a tutorial for mounting the filesystem, and you can install the tar and xz commands using Homebrew.

  1. Download the latest RetroPie image and flash an SD card (or other volume) with it
  2. Download the latest NOOBS release. You will need the full NOOBS download (not NOOBS Lite) since we will be using the included Raspberry Pi OS image as a base.
  3. While that downloads, write down the full sizes of the two partitions on the RetroPie SD card ('boot' and 'retropie' as of this writing). You will need them later. (OS X users: type diskutil list at the command line to get this easily, Linux users: type df -h in the terminal.)
  4. Create the .tar file of the main RetroPie filesystem (the 'retropie' partition). From the command line on your primary computer, navigate to where the 'retropie' partition is mounted (on OS X, try cd /Volumes/retropie). The command is sudo tar -cvpf ~/Desktop/retropie.tar ./* and this will create the retropie.tar file on your desktop.
  5. Write down the size of retropie.tar in megabytes.
  6. Navigate to your desktop (or wherever you saved the tarball) with cd ~/Desktop/ and compress the tarball with the command xz -9 -e -v retropie.tar. This will take some time.
  7. Now we need to do the same thing to the 'boot' partition, but tar apparently doesn't like FAT-formatted volumes. So... Copy the contents of the 'boot' partition to a folder on your hard drive. I used ~/Desktop/rpi/boot.
  8. From the command line, navigate to the 'boot' folder you just created. The command is sudo tar -cvpf ~/Desktop/boot.tar ./* and this will create the boot.tar file on your desktop.
  9. Write down the size of boot.tar in megabytes.
  10. Navigate to your desktop (or wherever you saved the tarball) with cd ~/Desktop/ and compress the tarball with the command xz -9 -e -v boot.tar. This won't take long, not nearly as long as the 'retropie' tarball.
  11. Hopefully NOOBS has finished downloading by now. Unzip it, and open up the 'os' folder. Duplicate the 'Raspberry Pi OS full' folder and rename it 'RetroPie'.
  12. Open up 'partitions.json' in your favorite (or second-favorite) text editor and make the following changes:
    • Change the label on the root partition to read retropie.
    • Change the value for parition_size_nominal for both boot and retropie to be the values from step 3 in megabytes. Since this is used by NOOBS to determine how much space will be on the SD card after install, it's better to round up than down. (Ex: a 59.8 MB partition would have a value of 60. A 1.9 GB partition would have a value of around 2000.)
      • Change the value for uncompressed_tarball_size to be the values from step 5 and 9
  13. If there is a 'flavours.json' file, throw it out. We don't need it.
  14. Open 'os.json' in whatever text editor is handy and make the following changes: * Change name to RetroPie * Optional) Change whatever else you want. At the very least you should probably change url to https://retropie.org.uk/ to provide proper credit to the awesome people who put this project together! * (Optional) Replace the 'Raspbian_Full.png' with 'RetroPie.png' from this image as an appropriate icon. * (Optional) Replace any or all of the files in the 'slides_vga' folder with approporiate images. These will be shown during the install process. * Replace the 'boot.tar.xz' and 'root.tar.xz' with the 'retropie.tar.xz' and 'boot.tar.xz' files you created in steps 6 and 10. * Format and prepare an SD card as described in the NOOBS Setup Guide. RetroPie should be available as an option in the OS list next to Rasperry Pi OS.
  15. Profit!

&&NOTE**: If the boot process is halting at the resizing of the ext4 partition, delete /etc/profile.d/01-expand.sh on the ext4 partition. NOOBS already resized the partition.

From the command line: 

sudo rm 01_expand.sh
If the 01-expand.sh file isn't yet in this directory, just delete bash_completion.sh by running: 
sudo rm bash_completion.sh