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USB Disk mode

If you soft-brick the CM3, you can attach it as a USB disk device and then change files to get it back into working order or read/write the entire disk image.

  • remove the bottom panel, toggle the switch (seen through a PCB cutout) from RUN to DISK.
  • plug the usb power directly into a computer.



first you'll need to get rpiboot (or comparable) installed for your os.


for debian-based distros,

sudo apt-get install libusb-1.0-0-dev
git clone --depth=1
cd usbboot

(for other linux distros, see the rpi docs.)

mac os

this assumes homebrew is installed.

brew install libusb
git clone --depth=1
cd usbboot


once installed, run rpiboot (note the sudo)

sudo ./rpiboot

output should look something like:

Waiting for BCM2835/6/7
Sending bootcode.bin
Successful read 4 bytes
Waiting for BCM2835/6/7
Second stage boot server
File read: start.elf
Second stage boot server done

next, find the name of the norns disk.


a disk will show up in /dev/sd? (normally something like /dev/sdb).

mac os

run diskutil list and note the name (norns is 3.9 GB so that's a good clue). the name will be something like disk3.

on mac os, it's important to unmount the disk before imaging (diskutil unmountDisk /dev/disk<disk_name>). a successful command will look something like:

[~/norns] $ diskutil unmountDisk /dev/disk3
Unmount of all volumes on disk3 was successful

copy the image

to copy image to norns:


sudo dd if=image.img of=/dev/sdb bs=4MiB status=progress conv=sparse

mac os

sudo dd if=<my_img>.img of=/dev/r<disk_name> bs=4m conv=sparse

(note the r prefix — this is important. it specifies the raw disk and your transfer will be far slower without it; for details, see this thread.)

if you want to see progress (it will take a while!), type ctrl+t to send a SIGINFO command which will cause dd to dump status; for example, something like:

load: 2.24  cmd: dd 55210 uninterruptible 0.06u 7.48s
142+0 records in
141+0 records out
591396864 bytes transferred in 313.867907 secs (1884222 bytes/sec)

copy the image (from norns)

reverse of/if to copy from norns

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