Replace Oracle Cloud Linux with Debian remotely

convert2deb.sh

[02/22/2025]

Refs:
1. http://mirror.cs.pitt.edu/archlinux/iso/2023.09.01/archlinux-bootstrap-2023.09.01-x86_64.tar.gz
2. https://dl-cdn.alpinelinux.org/alpine/v3.18/releases/x86_64/alpine-virt-3.18.0-x86_64.iso
3. https://wiki.alpinelinux.org/wiki/Replacing_non-Alpine_Linux_with_Alpine_remotely
4. https://www.debian.org/releases/bookworm/amd64/apds03.en.html

See also:
1. Convert to Debian   https://gist.github.com/zengxinhui/ee0ad6b7c7f99e2ead6cd0d2bd6641fd
2. Convert to arch x64 https://gist.github.com/zengxinhui/f328fdce54f5039689ee3aa4e91fc805
3. Convert to arch arm https://gist.github.com/zengxinhui/01afb43b8d663a4232a42ee9858be45e

Requirement:
  Console access.

# Prepare alpine linux, which can be configured to run from ram only.
# Alpine is leveraged to do the conversion.
# In any linux(ubuntu/debian/arch tested) become root first:
sudo su -
cd /tmp && wget https://dl-cdn.alpinelinux.org/alpine/v3.18/releases/x86_64/alpine-virt-3.18.0-x86_64.iso
dd if=alpine-virt-3.18.0-x86_64.iso of=/dev/sda && sync && reboot

# In Alpine with console:
# [Bring up networking]
ip li set eth0 up
udhcpc eth0
# [Setup SSH, answer RET, yes, RET]
setup-sshd
# [set temp alpine password for alpine login over SSH]
passwd
# [At this point it's easier to use SSH to copy & paste. E.g. "ssh root@<vps ip>"]

# [Per Ref #3. Move alpine to ram only]
mkdir /media/setup
cp -a /media/sda/* /media/setup
mkdir /lib/setup
cp -a /.modloop/* /lib/setup
/etc/init.d/modloop stop
umount /dev/sda
mv /media/setup/* /media/sda/
mv /lib/setup/* /.modloop/

# [Setup apk and bring in pacman]
setup-apkrepos
# [enable community]
vi /etc/apk/repositories

apk update
apk add dosfstools e2fsprogs util-linux-misc debian-archive-keyring debootstrap arch-install-scripts

# [Disk partitioning & mounting]
# (use gpt table, set esp partition 15 size 256M), set root partition 1 size remaining)
# g, n, 15, RET, +256m, t, 1, n, RET, RET, RET, p, w
fdisk /dev/sda

ls /dev/sda*
# if sda1 or sda15 is missing, do "/etc/init.d/devfs restart"

mkfs.vfat /dev/sda15
mkfs.ext4 /dev/sda1

mount -t ext4 /dev/sda1 /mnt
mkdir /mnt/boot
mount /dev/sda15 /mnt/boot

# [Per Ref #4] Coffee time.
debootstrap --include systemd --arch amd64 bookworm /mnt/ http://ftp.us.debian.org/debian

arch-chroot /mnt/
# This is your debian root password. Choose carefully and remember it
passwd
cat > /etc/fstab << EOF
# /etc/fstab: static file system information.
#
# file system    mount point   type    options                  dump pass
/dev/sda1         /             ext4    defaults                 0    1
/dev/sda15        /boot         vfat    nosuid,nodev             0    2
proc              /proc         proc    defaults                 0    0
EOF

cat >> /etc/network/interfaces << EOF
auto lo
iface lo inet loopback

auto ens3
iface ens3 inet dhcp
EOF

cat > /etc/resolv.conf << EOF
nameserver 1.1.1.1
nameserver 4.2.2.2
nameserver 8.8.8.8
EOF

echo deb12 > /etc/hostname 

cat >> /etc/apt/sources.list << EOF
deb http://security.debian.org/ bookworm-security main
EOF

apt update && apt -y install linux-image-cloud-amd64 grub-efi-amd64 ssh

cat > ~/.ssh/authorized_keys << EOF
<your key here>
EOF

grub-install --target=x86_64-efi --efi-directory=/boot --bootloader-id=GRUB
vi /etc/default/grub
  # Better console. Comparison below:
  #GRUB_CMDLINE_LINUX_DEFAULT="quiet"
  GRUB_CMDLINE_LINUX_DEFAULT="console=ttyS0,115200"

  # Or use perl/sed to replace
  #   perl -pi.bak -e "s/quiet/console=ttyS0,115200/" /etc/default/grub
  #   sed   -i.bak -e "s/quiet/console=ttyS0,115200/" /etc/default/grub
grub-mkconfig -o /boot/grub/grub.cfg
exit
reboot