## Switch oracle-cloud-instances to Debian

# This is the way:

Credits:

• https://gist.github.com/ishad0w/10a536f82c79d3b890d04243634df806

#!/bin/bash
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/*
EOL

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="20231004-1523"

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)"
sleep 180

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!"

Original credits for this page:

• https://sj14.gitlab.io/post/2021/01-30-free-k8s-cloud-cluster/
• https://serverfault.com/questions/528075/is-it-possible-to-on-line-shrink-a-ext4-volume-with-lvm

# Resize rootfs without LVM

1. Create a ubuntu-instance
2. Connect to the node, using ubuntu as the username, become root.
3. Add the following files, make them executable, and rebuild initramfs.

/etc/initramfs-tools/hooks/resizefs

#!/bin/sh

set -e

PREREQS=""

prereqs() { echo "$PREREQS"; }

case $1 in
    prereqs)
        prereqs
        exit 0
    ;;
esac

. /usr/share/initramfs-tools/hook-functions

copy_exec /sbin/e2fsck
copy_exec /sbin/resize2fs

exit 0

/etc/initramfs-tools/scripts/local-premount/resizefs

#!/bin/sh

set -e

PREREQS=""

prereqs() { echo "$PREREQS"; }

case "$1" in
    prereqs)
        prereqs
        exit 0
    ;;
esac

# simple device example
/sbin/e2fsck -yf /dev/sda1
/sbin/resize2fs /dev/sda1 6G
/sbin/e2fsck -yf /dev/sda1

chmod +x /etc/initramfs-tools/hooks/resizefs /etc/initramfs-tools/scripts/local-premount/resizefs

update-initramfs -u && update-grub

4. Remove growpart and resizefs from /etc/cloud/cloud.cfg, and reboot.

   Filesystem      Size  Used Avail Use% Mounted on
   /dev/sda1       5.8G  1.8G  4.0G  32% /
   

5. Run cfdisk /dev/sda and resize sda1 as a partition with 10GB, resize rootfs with resize2fs /dev/sda1.
6. You now have a smaller root-fs.

## Debootstrap debian on amd64

1. apt update && apt install debootstrap -y
2. cfdisk /dev/sda, create a new 6gb partition
3. pvcreate /dev/sda2 && vgcreate base /dev/sda2 && lvcreate -L5G base –name root
4. mkfs.ext4 /dev/mapper/base-root -L root -m0 && mount /dev/mapper/base-root /mnt/
5. debootstrap bullseye /mnt http://deb.debian.org/debian
6. mount –bind /dev /mnt/dev; mount –bind /sys /mnt/sys; mount –bind /proc /mnt/proc; cp /etc/fstab /mnt/etc/fstab

mkdir -p /mnt/root/.ssh
chmod 0700 /mnt/root/.ssh
cp /home/ubuntu/.ssh/authorized_keys /mnt/root/.ssh/authorized_keys
chmod 0600 /mnt/root/.ssh/authorized_keys

8. chroot /mnt
9. apt install ssh sudo python3-simplejson lvm2 -y
10. sed ’s/cloudimg-rootfs/root/g’ -i /etc/fstab

echo 'auto ens3' > /etc/network/interfaces.d/repair
echo 'iface ens3 inet dhcp' >> /etc/network/interfaces.d/repair
systemctl enable systemd-networkd

12. mkdir /boot/efi && mount -a
13. apt install grub-efi-amd64 linux-image-amd64 -y
14. grub-install /dev/sda && update-grub
15. exit
16. reboot
17. delete ssh-key, and re-connect as root
18. pvcreate /dev/sda1
19. vgextend base /dev/sda1 && pvmove -n root /dev/sda2 /dev/sda1
20. vgreduce base /dev/sda2 && pvremove /dev/sda2
21. fdisk /dev/sda, delete sda2, resize sda1 to 20G
22. reboot
23. pvresize /dev/sda1 && lvresize -r -L20G /dev/base/root

## Debootstrap debian on arm64

1. Create a oracle-linux-instance
2. Connect to the node, using opc as the username, become root.
3. Remove swap, and oled-mount from /etc/fstab - unmount them or reboot
4. lvremove /dev/ocivolume/oled
5. lvcreate -L8G ocivolume –name debian
6. mkfs.ext4 /dev/mapper/ocivolume-debian -L root -m0 && mount /dev/mapper/ocivolume-debian /mnt/
7. Download dpkg, https://pkgs.org/download/dpkg ( yum install https://download-ib01.fedoraproject.org/pub/epel/8/Everything/aarch64/Packages/d/dpkg-1.20.9-4.el8.aarch64.rpm )
8. Download debootstrap, https://pkgs.org/download/debootstrap ( yum install https://download-ib01.fedoraproject.org/pub/epel/8/Everything/aarch64/Packages/d/debootstrap-1.0.126-1.nmu1.el8.noarch.rpm )
9. debootstrap bullseye /mnt http://deb.debian.org/debian
10. mount –bind /dev /mnt/dev; mount –bind /sys /mnt/sys; mount –bind /proc /mnt/proc; cp /etc/fstab /mnt/etc/fstab

mkdir -p /mnt/root/.ssh
chmod 0700 /mnt/root/.ssh
cp /home/opc/.ssh/authorized_keys /mnt/root/.ssh/authorized_keys
chmod 0600 /mnt/root/.ssh/authorized_keys

12. chroot /mnt
13. apt install ssh sudo python3-simplejson lvm2 -y
14. Edit /etc/fstab - replace ocivolume-root with ocivolume-debian - also adjust filesystem from xfs to ext4

echo 'auto enp0s3' > /etc/network/interfaces.d/repair
echo 'iface enp0s3 inet dhcp' >> /etc/network/interfaces.d/repair
systemctl enable systemd-networkd

16. mkdir /boot/efi && mount -a
17. apt install grub-efi-arm64 linux-image-arm64 -y
18. grub-install /dev/sda && update-grub
19. exit
20. reboot
21. delete ssh-key, and re-connect as root
22. lvremove /dev/ocivolume/root
23. pvresize –setphysicalvolumesize 20G /dev/sda3
24. cfdisk /dev/sda - create sda4, 10G
25. pvcreate /dev/sda4
26. vgextend ocivolume /dev/sda4 && pvmove -n debian /dev/sda3 /dev/sda4
27. vgreduce ocivolume /dev/sda3 && pvremove /dev/sda3
28. cfdisk /dev/sda, resize sda3 to 20G
29. pvcreate /dev/sda3
30. vgextend ocivolume /dev/sda3 && pvmove -n debian /dev/sda4 /dev/sda3
31. vgreduce ocivolume /dev/sda4 && pvremove /dev/sda4
32. cfdisk /dev/sda, re-create sda4, with remaining space
33. reboot