Simple script for migrating a debian-like OS to Arch

migrate-os.sh

#!/usr/bin/env bash

set -e

if [[ "${1}" == "bootstrap" ]]; then
    # Create an arch bootstrap system
    apt install -y vim curl zstd git

    cd /mnt
    git clone https://github.com/tokland/arch-bootstrap.git
    install -m 0755 arch-bootstrap/arch-bootstrap.sh /usr/local/bin/arch-bootstrap

    arch-bootstrap bootstrap

    mount --rbind /dev /mnt/bootstrap/dev
    mount --rbind /sys /mnt/bootstrap/sys
    mount --make-rslave /mnt/bootstrap/dev
    mount --make-rslave /mnt/bootstrap/sys
    mount --rbind /tmp /mnt/bootstrap/tmp
    mount -t proc /proc /mnt/bootstrap/proc

    cp /etc/resolv.conf /mnt/bootstrap/etc/resolv.conf
    cp /etc/fstab /mnt/bootstrap/etc/fstab

    chroot /mnt/bootstrap /bin/bash <<EOF
pacman -Syu base arch-install-scripts --noconfirm
EOF

    umount -R /mnt/bootstrap/{dev,sys,proc,tmp}

elif [[ "${1}" == "migrate" ]]; then
    # Migrate step A
    ## Repace current root with bootstrap
    mkdir -vp /sysfs
    curl -L https://busybox.net/downloads/binaries/1.31.0-i686-uclibc/busybox -o /sysfs/busybox
    chmod +x /sysfs/busybox

    export PATH=/sysfs

    busybox rm -rf /usr /var/* /srv /opt /'lost+found' /sbin /etc /media /bin /cdrom /lib* /tmp
    busybox cp -Pr /mnt/bootstrap/{etc,usr,opt,srv,tmp} /
    busybox cp -Pr /mnt/bootstrap/run/* /run/
    busybox cp -Pr /mnt/bootstrap/var/{cache,db,empty,games,lib,local,log,opt,spool,tmp} /var/
    busybox ln -sf /run /var/run
    busybox ln -sf /run/lock /var/lock
    busybox ln -sf /var/spool/mail /var/mail
    busybox ln -sf /var/lib/dbus/machine-id /etc/machine-id
    busybox ln -sf /usr/bin /bin
    busybox ln -sf /usr/bin /sbin
    busybox ln -sf /usr/lib /lib
    busybox ln -sf /usr/lib /lib64

    export PATH="${PATH}:/bin"

    # Migrate step B
    ## Create a new arch root with pacstrap and make that the default
    mkdir -v /mnt/arch

    pacstrap /mnt/arch base linux linux-firmware openssh vim grub
    cp /etc/resolv.conf /mnt/arch/etc/resolv.conf
    cp /etc/fstab /mnt/arch/etc/fstab

    set +e
    busybox rm -rf /usr /var /srv /opt /'lost+found' /sbin /etc /media /bin /cdrom /lib* /tmp /var /run/*
    set -e

    busybox cp -Pr /mnt/arch/{etc,usr,opt,srv,tmp,var} /
    busybox ln -sf /usr/bin /bin
    busybox ln -sf /usr/bin /sbin
    busybox ln -sf /usr/lib /lib
    busybox ln -sf /usr/lib /lib64

    rm -f /boot/initrd* /boot/vmlinuz*
    cp -P /mnt/arch/boot/* /boot/

    mkinitcpio -P


    echo 'ulfox' >/etc/hostname
    passwd <<PSWD
ulfox
ulfox
PSWD

    grub-mkconfig -o /boot/grub/grub.cfg

    systemctl enable --now sshd
fi