#!/usr/bin/env bash
set -euo pipefail

cd "$(dirname "$0")"

basedir=ubuntu-base

[[ ($# -le 0 || "$1" != "-f") && -d "$basedir" ]] && {
  echo >&2 "Warning: base directory already exists, use -f to force"
  exit 1
}

mkdir -p "$basedir"
curl -L 'http://cdimage.ubuntu.com/ubuntu-base/releases/20.04/release/ubuntu-base-20.04.1-base-amd64.tar.gz' | tar -C "$basedir" -xz

args=(
  --bind ubuntu-base /
  --ro-bind /etc/resolv.conf /etc/resolv.conf
  --tmpfs /tmp
  --dev /dev
  --proc /proc
  --new-session
  --unshare-all
  --share-net
  --die-with-parent
  --gid 0 --uid 0
  --chdir /
  --ro-bind chroot-initialise.sh /tmp/chinit.sh
  /bin/bash /tmp/chinit.sh
)
bwrap "${args[@]}"