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

    text = ''
       #!/bin/sh

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

      MOUNTED=$(zfs list -o mountpoint,mounted -H | awk '$NF == "yes" {$NF=""; print $0}' | sed 's/[[:space:]]*$//')

       MISSING=""
       for target in "$@"; do
          if ! echo "$MOUNTED" | grep -Fxq "$target"; then
             MISSING="$MISSING $target"
          fi
       done

       if [[ -n "$MISSING" ]]; then
          echo "FAILURE, missing:$MISSING" 1>&2
          exit 1
       fi
    '';
  };
}