Create a debian container on a zfs pool for usage with systemd-nspawn and machinectl https://wiki.wut.ee/en/sysadmin/systemd-nspawn_containers

create_container.sh

#!/bin/bash
set -euo pipefail
BASE="/var/lib/machines"
ZDATA="rpool/machines"

if [[ $EUID -ne 0 ]]; then
   echo "This script must be run as root" 1>&2
   exit 1
fi

function show_help {
    cat <<-EOF
Usage: $0 -h | -n NAME [-s SUITE] [-d]

Create a nspanw container called NAME

-h      help
-n      container name
-s      debian suite (default: bullseye)
-d      delete container
EOF
}

while getopts 'hn:s:d' flag; do
  case "${flag}" in
    h) show_help; exit 0;;
    n) name="${OPTARG}" ;;
    s) suite="${OPTARG}" ;;
    d) delete=1 ;;
    *) echo "Unexpected option ${flag}" ;;
  esac
done

SUITE=${suite:-bullseye}

if [[ -z ${name:-} ]]; then
    echo "Container name is unset"
    echo
    show_help
    exit;
else
    echo "Container name is $name and suite is ${SUITE}"
fi

if [[ -n ${delete:-} ]]; then
   zfs destroy -r "${ZDATA}/$name"
   exit 0
fi

zfs create "${ZDATA}/${name}"

APT_CACHE_DIR="/var/cache/apt/archives"

if [[ -d ${APT_CACHE_DIR} ]]; then
    CACHE_ARGS="--cache-dir=${APT_CACHE_DIR}"
else
    CACHE_ARGS=""
fi

debootstrap ${CACHE_ARGS} "${SUITE}" "${BASE}/${name}"

if [ ! -d "$BASE/$name/root/.ssh" ]; then
    mkdir "$BASE/$name/root/.ssh"
    chmod 700 "$BASE/$name/root/.ssh"
    if [ ! -f "$BASE/$name/root/.ssh/authorized_keys" ]; then
        cp -v /root/.ssh/authorized_keys "$BASE/$name/root/.ssh/authorized_keys"
        chmod 600 "$BASE/$name/root/.ssh/authorized_keys"
        echo "added ssh keys to root"
    fi
else
    echo "ssh keys probably already added"
fi

if [[ -e "$BASE/$name/etc/resolv.conf" ]]; then
    rm "$BASE/$name/etc/resolv.conf"
fi

if [[ -e "$BASE/$name/etc/hostname" ]]; then
    rm "$BASE/$name/etc/hostname"
fi

systemd-nspawn --console=pipe -D "$BASE/$name" /bin/bash <<'EOF'
echo "Now running inside nspawn $(pwd)"

source /etc/os-release

if [[ "$ID" == "ubuntu" ]]; then
    sed -i '1 s/$/ restricted universe multiverse/' /etc/apt/sources.list
elif [[ "$ID" == "debian" ]]; then
    sed -i '1 s/$/ contrib non-free/' /etc/apt/sources.list
fi

apt-get update
apt-get install --yes --no-install-recommends locales dbus ssh

echo "locales locales/default_environment_locale select en_US.UTF-8" | debconf-set-selections
echo "locales locales/locales_to_be_generated multiselect en_US.UTF-8 UTF-8, et_EE.UTF-8 UTF-8" | debconf-set-selections
rm /etc/locale.gen
dpkg-reconfigure --frontend noninteractive locales
ln -fs /usr/share/zoneinfo/Europe/Tallinn /etc/localtime
dpkg-reconfigure -f noninteractive tzdata

apt install --yes --no-install-recommends neovim
update-alternatives --set editor /usr/bin/nvim

# Use systemd-resovled directly by configuring /etc/nsswitch.conf
apt install --yes --no-install-recommends libnss-resolve

systemctl enable systemd-networkd
systemctl enable systemd-resolved
EOF