mmdebstrap/tests/missing-dev-sys-proc-inside-the-chroot

#!/bin/sh
set -eu
export LC_ALL=C.UTF-8

[ {{ MODE }} = "unshare" ]
[ {{ VARIANT }} = "custom" ]

prefix=
if [ "$(id -u)" -eq 0 ] && [ "{{ MODE }}" != "root" ] && [ "{{ MODE }}" != "auto" ]; then
  if ! id "${SUDO_USER:-user}" >/dev/null 2>&1; then
    if [ ! -e /mmdebstrap-testenv ]; then
      echo "this test modifies the system and should only be run inside a container" >&2
      exit 1
    fi
    useradd --home-dir "/home/${SUDO_USER:-user}" --create-home "${SUDO_USER:-user}"
  fi
  prefix="runuser -u ${SUDO_USER:-user} --"
fi

# do not install base-files, so that /proc, /sys and /dev are missing
$prefix {{ CMD }} --mode={{ MODE }} --variant={{ VARIANT }} \
  --setup-hook='for dir in bin lib lib32 lib64 libo32 libx32 sbin; do ln -s "usr/$dir" "$1/$dir"; done' \
  --include=dpkg,dash,diffutils,coreutils,libc-bin,sed \
  {{ DIST }} /dev/null {{ MIRROR }}