This page will show a method how to install and get ssh access using dropbear.

The steps below require the following dependencies. Install them first:

sudo apt-get install git build-essential libncurses-dev

The dropbear binary can be easily built using buildroot. For this, we clone the buildroot-at91 repository because the AT91 architecture is close to the Allwinner V3s ARM Cortex A7 CPU. After git clone, cd into the repository.

git clone https://github.com/linux4sam/buildroot-at91.git
cd buildroot-at91

Since we do not have the same build environment as flashforge had, we will create a static build of dropbear. This requires to modify the dropbear package file in buildroot:

sed -i "s/disable-static/enable-static/g" package/dropbear/dropbear.mk

Then we need to configure buildroot for the right processor architecture and target software. Either download the configuration to build dropbear or configure manually, as shown further below:

mv .config .config_ORIG
wget -O .config https://www.auditeon.com/xyz/flashforge_dropbear_br2023.10.config

make menuconfig

Then set the following options accordingly:

Target options:
  Target Architecture (Arm (little endian))
  Target Architecture Variant (cortex-A7)
  Target ABI (EABI)
  Floating point strategy (VFPv4)
  ARM instruction set (ARM)
  Target Binary Format (ELF)

Toolchain:
  C library (glibc)
  Kernel Headers (Linux 6.1.x kernel headers)
  *** Glibc Options *** -> Enable compatibility shims to run on older kernels (enable this option)

Build options:
  strip target binaries (Enable this option)
  libraries (both static and shared)  <-- this will set BR2_SHARED_STATIC_LIBS=y
                                          for dropbear, together with patching
                                          packages/dropbear/dropbear.mk
Target packages:
  Networking applications --->
    * dropbear  (enable this option)
      * client programs  (enable this option)
      * optimize for size  (enable this option)

Go back to the main screen (click twice on exit) and click on Save

make

This step may take about 20 minutes (core i7-1370P x 20). When done, verify if dropbear is correctly built:

file output/target/usr/sbin/dropbear

We should see the following:

dropbear: ELF 32-bit LSB executable, ARM, EABI5 version 1 (GNU/Linux), statically linked, for GNU/Linux 3.2.0, stripped 

To get SSH on the printer, we will create a special USB stick. Insert an empty FAT formatted USB stick in your PC and copy dropbear to the main directory:

cp output/target/usr/sbin/dropbear /media/$USER/USBSTOR/

Replace USBSTOR with the name of the USB stick.

Write following script to the main directory of the USB stick with the name flashforge_init.sh

#!/bin/sh
set -x
 
WORK_DIR=`dirname $0`
 
MACHINE=Creator3Pro
PID=0014
 
#Test the machine's architecture and quit immediately if there's an error.
CHECK_ARCH=`uname -m`
if [ "${CHECK_ARCH}" != "armv7l" ];then
    echo "Machine architecture error."
    echo ${CHECK_ARCH}
    exit 1
fi
 
 
cat $WORK_DIR/start.img > /dev/fb0
 
#create_key
# 1. copy dropbear to /usr/sbin/
cp $WORK_DIR/dropbear /usr/sbin/dropbear
chmod 755 /usr/sbin/dropbear
 
# 2. create a symlink dropbearkey and dropbearconvert to dropbear in /usr/sbin
ln -s /usr/bin/dropbearkey /usr/sbin/dropbear
ln -s /usr/bin/dropbearconvert /usr/sbin/dropbear
 
# 3. create a symlink scp to dropbear in /usr/bin
ln -s /usr/sbin/dropbear /usr/bin/scp
 
# 4. create rsa key in /etc/dropbear/ (e.g. /etc/dropbear/dropbear_rsa_host_key)
mkdir -p /etc/dropbear
dropbearkey -t rsa -f /etc/dropbear/dropbear_rsa_host_key
 
# 5. Add dropbear as an init.d script
cat << 'EOF' > /etc/init.d/S50dropbear
#!/bin/sh
#
# S50dropbear        Starts dropbear.
#
# please note: if not added in rcS like:
# ifconfig eth0 hw ether 88:A9:A7:93:CD:EF
# the MAC address may change everytime when the board restarts.
 
# Make sure dropbearkey exists
[ -f /usr/bin/dropbearkey ] || exit 0
 
# Make sure dropbear exists
[ -f /usr/sbin/dropbear ] || exit 0
 
SSH_HOST_KEY=/etc/dropbear/dropbear_rsa_host_key
 
umask 077
 
start() {
    # check for public key, ssh-rsa type and for fingerprint
    if /usr/bin/dropbearkey -y -f ${SSH_HOST_KEY} | grep -q "Public key portion is" &&
      /usr/bin/dropbearkey -y -f ${SSH_HOST_KEY} | grep -q "ssh-rsa" &&
        /usr/bin/dropbearkey -y -f ${SSH_HOST_KEY} | grep -q "Fingerprint"; then
      printf "Starting sshd: "
      /usr/sbin/dropbear
      touch /run/dropbear.pid
      echo "OK"
    else
      # Create any missing keys
      printf "Creating ssh keys..."
      mkdir -p /etc/dropbear
      /usr/bin/dropbearkey -t rsa -f /etc/dropbear/dropbear_rsa_host_key
      start
    fi
}
stop() {
	printf "Stopping dropbear: "
	killall dropbear
	rm -f /run/dropbear.pid
	echo "OK"
}
restart() {
	stop
	start
}
 
case "$1" in
  start)
	start
	;;
  stop)
	stop
	;;
  restart|reload)
	restart
	;;
  *)
	echo "Usage: $0 {start|stop|restart}"
	exit 1
esac
 
exit $?
EOF
 
# 6. set file permissions for S50dropbear
chmod 755 /etc/init.d/S50dropbear
 
sync
cat $WORK_DIR/end.img > /dev/fb0
 
$WORK_DIR/play
 
exit 0
EOF
 
# 6. set file permissions for S50dropbear
chmod 755 /etc/init.d/S50dropbear
 
sync
cat $WORK_DIR/end.img > /dev/fb0
 
$WORK_DIR/play
 
exit 0

Download the following files:

• 0014
• end.img
• play
• start.img
• version.cfg
• dropbear <-- Either use your own build or take this file
• flashforge_init.sh <-- Either use the file which you created yourself or take this file

From this link: flashforge_dropbear_files.tar.bz2 and extract them to the USB stick.

1. Power off the printer
2. Insert the stick in the printer and power it on again.
3. After a few seconds dropbear should be installed.
4. Switch off the printer once again, remove the USB stick
5. Power on again. Dropbear should now be ready for use.

Test the ssh connection to the printer with following user: root