future-install-scripts/genfstab.in

#!/bin/bash
# shellcheck disable=SC2154 # optstring_*_option may export variables in runtime

shopt -s extglob

# m4_include() is recognized as a function definition
# shellcheck source=common disable=SC1073,SC1065,SC1064,SC1072
m4_include(common)

bytag=src
pseudofs=0

write_source() {
  local src spec comments=()

  src="$(mangle "$1")"
  local -A sources=([LABEL]="$(mangle "$(lsblk -rno LABEL "$1" 2>/dev/null)")"
                    [UUID]="$(lsblk -rno UUID "$1" 2>/dev/null)"
                    [PARTLABEL]="$(mangle "$(lsblk -rno PARTLABEL "$1" 2>/dev/null)")"
                    [PARTUUID]="$(lsblk -rno PARTUUID "$1" 2>/dev/null)"
  )

  if [[ ${sources["$bytag"]} ]]; then
    spec="$bytag"
    comments+=("$src")
  else
    spec=src
  fi

  for tag in "${!sources[@]}"; do
    if [[ ${sources["$tag"]} && "$tag" != "$spec" ]]; then
      comments+=("$tag=${sources["$tag"]}")
    fi
  done

  (( ${#comments[@]} )) && printf '# %s\n' "${comments[*]}"

  if [[ "$spec" != "src" ]]; then
    printf '%-20s' "$spec=${sources["$spec"]}"
  else
    printf '%-20s' "$src"
  fi
}

optstring_apply_quirks() {
  local varname="$1" fstype="$2"

  # SELinux displays a 'seclabel' option in /proc/self/mountinfo. We can't know
  # if the system we're generating the fstab for has any support for SELinux (as
  # one might install Arch from a Fedora environment), so let's remove it.
  optstring_remove_option "$varname" seclabel

  # Prune 'relatime' option for any pseudofs. This seems to be a rampant
  # default which the kernel often exports even if the underlying filesystem
  # doesn't support it. Example: https://bugs.archlinux.org/task/54554.
  if fstype_is_pseudofs "$fstype"; then
    optstring_remove_option "$varname" relatime
  fi

  case $fstype in
    btrfs)
      # Having only one of subvol= and subvolid= is enough for mounting a btrfs subvolume
      # And having subvolid= set prevents things like 'snapper rollback' to work, as it
      # updates the subvolume in-place, leaving subvol= unchanged with a different subvolid.
      if optstring_has_option "$varname" subvol; then
        optstring_remove_option "$varname" subvolid
      fi
      ;;
    f2fs)
      # These are Kconfig options for f2fs. Kernels supporting the options will
      # only provide the negative versions of these (e.g. noacl), and vice versa
      # for kernels without support.
      optstring_remove_option "$varname" noacl,acl,nouser_xattr,user_xattr
      ;;
  esac
}

usage() {
  cat <<EOF
usage: ${0##*/} [options] root

  Options:
    -f <filter>    Restrict output to mountpoints matching the prefix FILTER
    -L             Use labels for source identifiers (shortcut for -t LABEL)
    -p             Exclude pseudofs mounts (default behavior)
    -P             Include pseudofs mounts
    -t <tag>       Use TAG for source identifiers (TAG should be one of: LABEL,
                       UUID, PARTLABEL, PARTUUID)
    -U             Use UUIDs for source identifiers (shortcut for -t UUID)

    -h             Print this help message

genfstab generates output suitable for addition to an fstab file based on
the devices mounted under the mountpoint specified by the given root.

EOF
}

if [[ -z $1 || $1 = @(-h|--help) ]]; then
  usage
  exit $(( $# ? 0 : 1 ))
fi

while getopts ':f:LPpt:U' flag; do
  case $flag in
    f)
      prefixfilter="$OPTARG"
      ;;
    L)
      bytag=LABEL
      ;;
    P)
      pseudofs=1
      ;;
    p)
      pseudofs=0
      ;;
    t)
      bytag="${OPTARG^^}"
      ;;
    U)
      bytag=UUID
      ;;
    :)
      die "%s: option requires an argument -- '%s'" "${0##*/}" "$OPTARG"
      ;;
    ?)
      die "%s: invalid option -- '%s'" "${0##*/}" "$OPTARG"
      ;;
  esac
done
shift $(( OPTIND - 1 ))

(( $# )) || die 'No root directory specified'
root="$(realpath -mL "$1")"; shift

if ! mountpoint -q "$root"; then
  die '%s: not a mountpoint' "$root"
fi

# handle block devices
findmnt -Recvruno SOURCE,TARGET,FSTYPE,OPTIONS,FSROOT "$root" |
    while read -r src target fstype opts fsroot; do
  if (( ! pseudofs )) && fstype_is_pseudofs "$fstype"; then
    continue
  fi

  [[ "$target" = "$prefixfilter"* ]] || continue

  # default 5th and 6th columns
  dump=0 pass=2

  src="$(unmangle "$src")"
  target="$(unmangle "$target")"
  target="${target#"$root/"}"
  [[ "$target" != '/'* ]] && target="/$target"

  if (( ! foundroot )) && findmnt "$src" "$root" >/dev/null; then
    # this is root. we can't possibly have more than one...
    pass=1 foundroot=1
  fi

  # if there's no fsck tool available, then only pass=0 makes sense.
  if ! fstype_has_fsck "$fstype"; then
    pass=0
  fi

  if [[ "$fsroot" != "/" && "$fstype" != "btrfs" ]]; then
    # it's a bind mount
    mapfile -t bind_srcs < <(findmnt -uncevo TARGET "$src")
    for bind_src in "${bind_srcs[@]}"; do
      if [[ -d "$bind_src$fsroot" ]]; then
        src="$bind_src$fsroot"
        break
      fi
    done

    src="${src#"$root/"}"
    [[ "$src" != '/'* ]] && src="/$src"

    if [[ "$src" = "$target" ]]; then
      # hrmm, this is weird. we're probably looking at a file or directory
      # that was bound into a chroot from the host machine. Ignore it,
      # because this won't actually be a valid mount. Worst case, the user
      # just re-adds it.
      continue
    fi

    fstype=none
    opts+=',bind'
    pass=0
  fi

  # filesystem quirks
  case $fstype in
    fuseblk)
      # well-behaved FUSE filesystems will report themselves as fuse.$fstype.
      # this is probably NTFS-3g, but let's just make sure.
      if ! newtype="$(lsblk -no FSTYPE "$src")" || [[ -z $newtype ]]; then
        # avoid blanking out fstype, leading to an invalid fstab
        error 'Failed to derive real filesystem type for FUSE device on %s' "$target"
      else
        fstype="$newtype"
      fi
      ;;
  esac

  optstring_apply_quirks opts "$fstype"

  # write one line
  write_source "$src"
  printf '\t%-10s' "$(mangle "$target")" "$fstype" "$opts"
  printf '\t%s %s' "$dump" "$pass"
  printf '\n\n'
done

# handle swaps devices
{
  # ignore header
  read -r

  while read -r device type _ _ prio; do
    options=defaults
    if (( prio >= 0 )); then
      options+=",pri=$prio"
    fi

    # skip files marked deleted by the kernel
    [[ "$device" = *'\040(deleted)' ]] && continue

    if [[ "$type" = "file" ]]; then
      printf '%-20s' "${device#"${root%/}"}"
    elif [[ "$device" = "/dev/dm-"+([0-9]) ]]; then
      # device mapper doesn't allow characters we need to worry
      # about being mangled, and it does the escaping of dashes
      # for us in sysfs.
      write_source "$(dm_name_for_devnode "$device")"
    else
      write_source "$(unmangle "$device")"
    fi

    printf '\t%-10s\t%-10s\t%-10s\t0 0\n\n' none swap "$options"
  done
} </proc/swaps

# vim: et ts=2 sw=2 ft=sh: