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--- projects:3dprinting:flashforge_creator_3_pro_fan_fix:dropbear [2025/01/21 19:30] – created admin
+++ projects:3dprinting:flashforge_creator_3_pro_fan_fix:dropbear [2025/04/27 23:15] (current) – [buildroot + dropbear] admin
@@ Line 3: / Line 3: @@
 |  [[projects:3dprinting:flashforge_creator_3_pro_fan_fix | <- back to Flashforge Creator 3 pro overview page]]  |
-This page will show one way how to install and get ssh access using dropbear.
+This page will show a method how to install and get ssh access using dropbear.
+==== Prerequisites ====
+The steps below require the following dependencies. Install them first:
-==== building with busybox ====
+  sudo apt-get install git build-essential libncurses-dev
-Buildroot options:
-  * BR2_SHARED_STATIC_LIBS=y
-For dropbear we need a statically linked file. See [[https://github.com/maximeh/buildroot/blob/master/package/dropbear/dropbear.mk|here]] for more details how to setup accordingly.
+==== buildroot + dropbear ====
+The dropbear binary can be easily built using [[https://buildroot.org/|buildroot]]. For this, we clone the [[https://github.com/linux4sam/buildroot-at91.git|buildroot-at91]] repository because the AT91 architecture is close to the Allwinner V3s ARM Cortex A7 CPU. After git clone, cd into the repository.
-Also see [[https://buildroot.org/downloads/manual/manual.html#adding-board-support|Chapter 17. Adding support for a particular board]] in the buildroot documentation. There it explains how to create a template for a new board.
+  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 can not rely on the system's libraries and will need to 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
+=== Configure buildroot manually ===
+  make menuconfig
+Then set the following options accordingly:
+<code>
+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)
+</code>
+Go back to the main screen (click twice on exit) and click on Save
+==== Start building cross compiler and dropbear ====
+  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
+===== Create a USB stick =====
+To get SSH on the printer, we need to put some files on a USB stick, mimicking as if the printer would do a firmware update. 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
-In the ELF file of the play application, following library defines are shown:
 <code bash>
-c6 ds "GCC_3.5"
+#!/bin/sh
-ce ds "GLIBC_2.4"
+set -x
-d8 ds "CXXABI_1.3"
-e3 ds "GLIBCXX_3.4"
+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
 </code>
+After copying dropbear and flashforge_init.sh to a USB stick, download the following files from [[https://drive.google.com/file/d/11mXjpSDyMnloJLvtLTWBgSO6f1Hx_eiH/view?usp=drive_link|the official Flashforge 1.4.0 release]] and copy them to the USB stick as well.
+  * 0014
+  * end.img
+  * play
+  * start.img
+  * version.cfg
+Alternatively you may download all the files together in one tar.bz2 archive from here [[https://www.auditeon.com/xyz/flashforge_dropbear_files.tar.bz2|flashforge_dropbear_files.tar.bz2]] and extract them to the USB stick.
+===== Install dropbear to the printer =====
+  - Power off the printer
+  - Insert the stick in the printer and power it on again.
+  - After a few seconds dropbear should be installed.
+  - Switch off the printer once again, remove the USB stick
+  - Power on again. Dropbear should now be ready for use.
+Test the ssh connection to the printer with following user: root\\
+The password for user root you should have already modified as described in the [[projects:3dprinting:flashforge_creator_3_pro_fan_fix:root_access|following page]].

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