DIY install debian on Oracle Cloud Infrastructure ( Free Tier )

reinstall_VPS_from_inside.sh

# should works on any cloud-init enabled hypervisor (openstack.. )

# start from a ubuntu minimal install
# we need to shrink down the used space to move it in a tmpfs of 700MB

while ! ssh -o ConnectTimeout=2 -p 22 ubuntu@$instanceIP; do sleep 1; done

# make sure we are on the highest kernel, so we can delete all the others ...
sudo apt update && sudo apt dist-upgrade -y && sudo apt install lsof && sudo reboot

sudo snap remove --purge  oracle-cloud-agent && sudo snap remove --purge core18 && sudo snap remove --purge snapd && sudo sudo apt -y purge snapd && sudo rm -rf ~/snap /snap /var/cache/snapd
sudo apt purge -y $(dpkg-query -Wf '${Package}\n' | grep header)  $(apt list --installed | grep -oP "^linux.*\d\d\d\d-oracle" | grep -v "$(uname -r)") linux-modules-extra-$(uname -r) lxc* lxd* vim* && sudo apt -y autoremove && sudo apt -y autoclean && sudo apt -y clean  
sudo rm -rf /var/log/* /var/lib/apt/lists/*


# ok, the disk usage of / should be less than 600MB now

cd /
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 /
unshare -m
pivot_root . old_root

/usr/sbin/sshd -D -p 1022 &

iptables -I INPUT -p tcp -m state --state NEW -m tcp --dport 1022 -j ACCEPT

# reconnect on port 1022:

while ! ssh -o ConnectTimeout=2 -p 1022 ubuntu@$instanceIP; do sleep 1; done

# now the root storage is the RAM 

pkill agetty
pkill dbus-daemon
pkill atd
pkill iscsid
pkill rpcbind
pkill unattended-upgrades
kill 1 

# check with "lsof /old_root" that there is no remaining process 

umount -l /dev/sda1

# check :

df -h 
lsblk 

# the disk should be unmount 
# now, just copy the debian cloud image on the disk.

# curl https://cdimage.debian.org/cdimage/openstack/current/debian-10-openstack-amd64.raw | dd of=/dev/sda bs=1M

# update : 
# curl -L  https://cdimage.debian.org/cdimage/openstack/testing/debian-testing-openstack-amd64.raw | dd of=/dev/sda bs=1M

# curl -L https://cdimage.debian.org/images/cloud/bullseye/latest/debian-11-genericcloud-amd64.raw | dd of=/dev/sda bs=1M

curl -L https://cloud.debian.org/cdimage/cloud/bullseye/latest/debian-11-generic-amd64.tar.xz | tar -OJxvf - disk.raw | dd of=/dev/sda bs=1M

sync

reboot

while ! ssh -o ConnectTimeout=2 -p 22 debian@$instanceIP; do sleep 1; done