Debian 12 on Oracle Cloud (Free Tier) - (AMD64/ARM64)

oci_ubuntu_to_debian.multiarch.sh

#!/bin/bash
trap "exit" INT
echo -e "\nHost:"
ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -p 22 ubuntu@$1 \
    'uname -a && arch && uptime && sudo touch /home/ubuntu/.hushlogin /root/.hushlogin'

echo -e "\nAdding temporary SSH-key for Ubuntu root user..."
ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -p 22 ubuntu@$1 \
    'sudo cat /home/ubuntu/.ssh/authorized_keys | sudo tee /root/.ssh/authorized_keys'

echo -e "\nSystem trimming..."
ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -p 22 root@$1 -T <<'EOL'
export DEBIAN_FRONTEND=noninteractive
snap remove --purge oracle-cloud-agent && snap remove --purge core18
apt-get purge -y linux-* lxc* lxd* vim* snapd* python*
apt-get update && apt-get install -y lsof
apt-get -y autoremove --purge
apt-get -y autoclean
rm -rf /var/log/* /var/lib/apt/* /var/cache/apt/*
df -h
EOL
echo "Check free space! for "/" mountpoint. <=700mb"
waittime=15
while [ $waittime -gt 0 ]; do
   echo -ne "$waittime\033[0K\r"
   sleep 1
   : $((waittime--))
done

echo -e "\nPreparing system..."
ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -p 22 root@$1 -T <<'EOL'
cd /
echo "Mounting tmpfs..."
mount -t tmpfs -o size=700m tmpfs mnt && tar --one-file-system -c . | tar -C /mnt -x
mount --make-private -o remount,rw /
mount --move dev mnt/dev && mount --move proc mnt/proc
mount --move run mnt/run && mount --move sys mnt/sys
sed -i "/^[^#]/d;" mnt/etc/fstab
echo "tmpfs / tmpfs defaults 0 0" >> mnt/etc/fstab
cd mnt && mkdir old_root
mount --make-private /
sleep 2

echo "Changing the root mount..."
unshare -m
pivot_root . old_root
sleep 5

echo "Starting SSH on 1022..."
iptables -I INPUT -p tcp -m state --state NEW -m tcp --dport 1022 -j ACCEPT
nohup /usr/sbin/sshd -D -p 1022 > /dev/null 2>&1 &
EOL

echo -e "\nFlashing the Debian image..."
ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -p 1022 root@$1 -T <<'EOL'
echo "Arch is $(arch)..."

IMAGEMIRROR="https://cloud.debian.org/images/cloud/bookworm"
IMAGEVERSION="debian-12-genericcloud"
IMAGEBUILD="20240701-1795"

for i in agetty dbus-daemon atd iscsid rpcbind unattended-upgrades; do pkill $i; done; kill 1; umount -l /dev/sda1
if [ $(arch) = "x86_64" ]
    then curl -L $IMAGEMIRROR/$IMAGEBUILD/$IMAGEVERSION-amd64-$IMAGEBUILD.tar.xz | tar -OJxvf - disk.raw | dd of=/dev/sda bs=1M; 
elif [ $(arch) = "aarch64" ]
    then curl -L $IMAGEMIRROR/$IMAGEBUILD/$IMAGEVERSION-arm64-$IMAGEBUILD.tar.xz | tar -OJxvf - disk.raw | dd of=/dev/sda bs=1M; 
else 
    echo Unsported architecture!
fi
sleep 5

echo "Syncing changes to the block storage..."
sync
sleep 5

echo "Rebooting into Debian!"
nohup sh -c 'echo "1" > /proc/sys/kernel/sysrq && sleep 5 && echo "b" > /proc/sysrq-trigger' > /dev/null 2>&1 &
EOL

echo -e "\nWaiting until Debian starts... (3 min)"
waittime=180
while [ $waittime -gt 0 ]; do
   echo -ne "$waittime\033[0K\r"
   sleep 1
   : $((waittime--))
done

echo -e "\nAdding temporary SSH-key for Debian root user..."
ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -p 22 debian@$1 \
    'sudo cat /home/debian/.ssh/authorized_keys | sudo tee /root/.ssh/authorized_keys'

echo -e "\nDebian inititialisation..."
ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=ERROR -p 22 root@$1 -T <<'EOL'
export DEBIAN_FRONTEND=noninteractive
echo "deb http://deb.debian.org/debian/ bookworm main contrib non-free non-free-firmware
deb http://deb.debian.org/debian/ bookworm-updates main contrib non-free non-free-firmware
deb http://deb.debian.org/debian/ bookworm-backports main contrib non-free non-free-firmware
deb http://security.debian.org/debian-security/ bookworm-security main contrib non-free non-free-firmware" > /etc/apt/sources.list
apt-get update && apt-get install -y locales-all
rm -rf /root/.ssh/
sync
reboot
EOL

sleep 10
echo -e "\nDone!"

with SSH (public key) access to a remote Oracle Cloud Instance

Where do I put the ssh key address while doing /oci_ubuntu_to_debian.multiarch.sh my_vps_ip_address ?

This doesn't work: /oci_ubuntu_to_debian.multiarch.sh my_vps_ip_address -i ~/some_folder/my_public_ssh_key.pub

edit: I was accidentally using pub key, also I added -i ~/some_folder/my_public_ssh_key manually into the file wherever we login