final: prev: {
  ensureZfsMounts = prev.writeShellApplication {
    name = "zfsEnsureMounted";
    runtimeInputs = with prev; [
      zfs
      gnugrep
      gawk
      coreutils
    ];

    text = ''
      #!/bin/sh -x

      if [[ "$#" -eq "0" ]]; then
         echo "no arguments passed"
         exit 1
      fi

      TARGETS=$(echo "$@" | sort | uniq)
      MOUNTED=$(zfs list -o mountpoint,mounted -H | awk '$2 == "yes" {print $1}' | sort | uniq)
      NUM_MATCHED=$(echo "$MOUNTED" | grep -Ec "$(echo "$@" | tr ' ' '\|')") # does not properly handle paths with strings
      if [[ "$NUM_MATCHED" -eq "$#" ]]; then
         exit 0
      fi

      FOUND=$(printf "%s\n%s" "$TARGETS" "$MOUNTED" | sort | uniq -c | awk '$1 == "2" {print $2}' | sort)
      MISSING=$(printf "%s\n%s" "$FOUND" "$TARGETS" | sort | uniq -u | sort)

      echo "FAILURE, missing: $MISSING" 1>&2
      exit 1
    '';
  };
}