xbps-chroot

#!/bin/bash

SELF_SRC="$(realpath ${BASH_SOURCE})"
SELF_DIR="$(dirname "${SELF_SRC}")"

function guard() {
  local code="${1}"
  local message="${2}"

  if [ "${code}" -ne 0 ]; then
    echo "${message} (${code})"
    exit 1
  fi
}

function purge() {
  local rootfs="${1}"
  local buildfs="${2}"

  mkdir -p "${rootfs}" "${buildfs}"
  umount -qR "${rootfs}"

  find "${rootfs}" -mindepth 1 -delete
  find "${buildfs}" -mindepth 1 -delete
}

function setup() {
  local rootfs="${1}"
  local buildfs="${2}"

  mount -t overlay overlay -o lowerdir=/,upperdir="${buildfs}",workdir="${rootfs}" "${rootfs}"
  guard $? 'could not mount overlayfs onto root/build directories'

  mount -t proc /proc "${rootfs}/proc"
  guard $? 'could not mount procfs into overlayfs'

  mount -t sysfs /sys "${rootfs}/sys"
  guard $? 'could not mount sysfs into overlayfs'

  mount --rbind /dev "${rootfs}/dev"
  guard $? 'could not bind mount /dev into overlayfs'

  mount --rbind /run "${rootfs}/run"
  guard $? 'could not bind mount /run into overlayfs'

  mount --bind "${SELF_DIR}" "${rootfs}/${SELF_DIR}"
  touch "${rootfs}/.chroot"
}

function main() {
  local tmpdir='/tmp/xbps-src'

  test ! -f '/.chroot'
  guard $? 'already in a chroot'

  purge "${tmpdir}"/{rootfs,buildfs}

  setup "${tmpdir}"/{rootfs,buildfs}
  chroot "${tmpdir}"/rootfs "${SELF_DIR}/xbps-src" "${@:1}"

  purge "${tmpdir}"/{rootfs,buildfs}
}

main "${@}"