Automatically unlock a remote luks drive

gistfile1.txt

#!/bin/bash

# client: ssh-keygen -f $keyname -t rsa -b 4096 -o -a 100
# server: apt install dropbear-initramfs 
# server: add generated public key of keypair to /etc/dropbear/initramfs/authorized_keys
# server: update-initramfs -u

REMOTE_USER="root"
REMOTE_HOST="192.168.x.xxx"
IDENTITY_FILE="~/.ssh/lukstest"
# can be generated via ssh-keyscan -H "$REMOTE_HOST" >"$KNOWNHOSTS_FILE"
KNOWNHOSTS_FILE="/path/to/known_hosts"
SCRIPT_PATH="cryptroot-unlock"

echo -n "Enter LUKS passphrase to send: "
read -s PASSPHRASE
echo

while true; do
    echo -n "$PASSPHRASE" | ssh -o StrictHostKeyChecking=yes -o UserKnownHostsFile="$KNOWNHOSTS_FILE" -i "$IDENTITY_FILE" -T -o "SendEnv=TERM" "$REMOTE_USER@$REMOTE_HOST" "$SCRIPT_PATH"

    if [ $? -eq 0 ]; then
        echo "Successfully unlocked"
    fi

    sleep 5
done