Ubuntu – Ubuntu will not boot into busybox for remote LUKS decryption using dropbear

After what feels like an eternity of deep diving into Google and trial and error, I finally got this figured out.

Here are the steps I took relative to the steps I outlined in the question:

1. Removed the script in the blogpost referenced in the question
2. In the crossfire of trial and error, ended up removing ifconfig eth0 0.0.0.0 down from usr/share/initramfs-tools/scripts/init-bottom/dropbear that step 6 in the blogpost outlined; I never added it back but never needed it

3. Modified and added the following scripts from this post:

   # Comment lines in /usr/share/initramfs-tools/scripts/local-top/cryptroot as follows:
   #
   if [ -z "$cryptkeyscript" ]; then
   cryptkey="Unlocking the disk $cryptsource ($crypttarget)\nEnter passphrase: "
   #if [ -x /bin/plymouth ] && plymouth --ping; then
   # cryptkeyscript="plymouth ask-for-password --prompt"
   # cryptkey=$(echo -e "$cryptkey")
   #else
   cryptkeyscript="/lib/cryptsetup/askpass"
   #fi
   fi
   
   
   
   # Add /usr/share/initramfs-tools/hooks/cryptroot_unlock and make executable
   #
   # Prompt to unlock LUKS encrypted root partition remotely
   #
   # See linked post for sources and acknowledgements
   #
   #!/bin/sh
   PREREQ=""
   prereqs()
   {
   echo "$PREREQ"
   }
   case $1 in
   prereqs)
   prereqs
   exit 0
   ;;
   esac
   . /usr/share/initramfs-tools/hook-functions
   #
   # Begin real processing
   #
   SCRIPTNAME=unlock
   # 1) Create script to unlock luks partitions
   cat > ${DESTDIR}/bin/${SCRIPTNAME} << '__EOF'
   #!/bin/sh
   /lib/cryptsetup/askpass "Enter volume password: " > /lib/cryptsetup/passfifo
   __EOF
   chmod 700 ${DESTDIR}/bin/${SCRIPTNAME}
   # 2) Enhance Message Of The Day (MOTD) with info how to unlock luks partition
   cat >> ${DESTDIR}/etc/motd << '__EOF'
   To unlock root-partition run "${SCRIPTNAME}"
   __EOF
   
   
   
   # Add /usr/share/initramfs-tools/scripts/local-bottom/dropbear_kill_clients and make executable
   #
   #
   # Kills all DropBear client sessions if InitRAMFS is left
   #
   # See linked post for sources and acknowledgements
   #
   #!/bin/sh
   PREREQ=""
   prereqs()
   {
   echo "$PREREQ"
   }
   case $1 in
   prereqs)
   prereqs
   exit 0
   ;;
   esac
   #
   # Begin real processing
   #
   NAME=dropbear
   PROG=/sbin/dropbear
   # get all server pids that should be ignored
   ignore=""
   for server in `cat /var/run/${NAME}*.pid`
   do
   ignore="${ignore} ${server}"
   done
   # get all running pids and kill client connections
   for pid in `pidof "${NAME}"`
   do
   # check if correct program, otherwise process next pid
   grep -F -q -e "${PROG}" "/proc/${pid}/cmdline" || {
   continue
   }
   # check if pid should be ignored (servers)
   skip=0
   for server in ${ignore}
   do
   if [ "${pid}" == "${server}" ]
   then
   skip=1
   break
   fi
   done
   [ "${skip}" -ne 0 ] && continue
   # kill process
   echo "$0: Killing ${pid}..."
   kill -KILL ${pid}
   done
   

After modifying and adding those scripts, dropbear was able to start, but my network device was failing to connect to the network, so I was still unable to connect to the server.

I finally discovered by using ls /sys/class/net that my network adapter was not called eth0; apparently that is an old notation no longer used by recent versions of Ubuntu, and since all the posts I have found are old if not ancient, eth0 is all I found references to.

So, armed with that information and a few more snippets I found from other sources, I modified initramfs.conf as follows:

4. Modified the DEVICE= portion of /etc/initramfs-tools/initramfs.conf to read:

   DEVICE=<name of network adapter discovered using ls /sys/class/net>
   IP=<Static IP Address>::<Default Gateway>:<Subnet Mask>::<name of network adapter>:off
   

5. Updated initramfs (sudo update-initramfs -u)

Now dropbear connects to the network and I can connect to the server and unlock remotely.