How to automate filesystem expansion

Question

I have 3 commands I have to run manually to expand my USB filesystem. I am looking for help on automating this in a script that does not need user input at all. I understand you can expand the filesystem using command "raspi-config --expand-rootfs" but I need to combine all these commands into a script.

sudo bash
sed -E 's/mmcblk0p?/sda/' /usr/bin/raspi-config | bash

-- THEN manually expand filesystem --

Answer 1

Rather than adapting raspi-config to your needs, wouldn't it be easier to write your own script to expand the root FS?

parted /dev/sda resizepart 2 XXXX # resize /dev/sda2 to XXXX in MB
parted /dev/sda resizepart 2 100% # or just use all available space
resize2fs /dev/sda2 # resize filesystem

(obviously, you don't need both parted lines in an actual script, choose the one that fits your use case)

Take a look inside raspi-config or here if you need to find out the partition size dynamically.

Answer 2

There is no need to "find the full size of the filesystem" - by default fdisk will use all space (and will indeed suggest the size). The only precaution is the need to ensure the correct partition START is selected.

If you REALLY want to use parted you can use a command like

cat /sys/block/mmcblk0/size 

to get the size (you would need to use the appropriate disk identifier).

See https://raspberrypi.stackexchange.com/a/49921/8697 - this is a generic Linux procedure that should work on any MBR disk

This CAN be scripted, but as the link points out "scripting fdisk is far from straightforward and you will probably never need to repeat".

The script I used to resize images - could be adapted, but be warned it takes so long to get it right you would be better to do it manually.

Alternatively you could adapt the script Raspbian uses:-

#!/bin/sh

reboot_pi () {
  umount /boot
  mount / -o remount,ro
  sync
  if [ "$NOOBS" = "1" ]; then
    if [ "$NEW_KERNEL" = "1" ]; then
      reboot -f "$BOOT_PART_NUM"
    else
      echo "$BOOT_PART_NUM" > "/sys/module/${BCM_MODULE}/parameters/reboot_part"
    fi
  fi
  echo b > /proc/sysrq-trigger
  sleep 5
  exit 0
}

check_commands () {
  if ! command -v whiptail > /dev/null; then
      echo "whiptail not found"
      sleep 5
      return 1
  fi
  for COMMAND in grep cut sed parted fdisk findmnt partprobe; do
    if ! command -v $COMMAND > /dev/null; then
      FAIL_REASON="$COMMAND not found"
      return 1
    fi
  done
  return 0
}

check_noobs () {
  if [ "$BOOT_PART_NUM" = "1" ]; then
    NOOBS=0
  else
    NOOBS=1
  fi
}

get_variables () {
  ROOT_PART_DEV=$(findmnt / -o source -n)
  ROOT_PART_NAME=$(echo "$ROOT_PART_DEV" | cut -d "/" -f 3)
  ROOT_DEV_NAME=$(echo /sys/block/*/"${ROOT_PART_NAME}" | cut -d "/" -f 4)
  ROOT_DEV="/dev/${ROOT_DEV_NAME}"
  ROOT_PART_NUM=$(cat "/sys/block/${ROOT_DEV_NAME}/${ROOT_PART_NAME}/partition")

  BOOT_PART_DEV=$(findmnt /boot -o source -n)
  BOOT_PART_NAME=$(echo "$BOOT_PART_DEV" | cut -d "/" -f 3)
  BOOT_DEV_NAME=$(echo /sys/block/*/"${BOOT_PART_NAME}" | cut -d "/" -f 4)
  BOOT_PART_NUM=$(cat "/sys/block/${BOOT_DEV_NAME}/${BOOT_PART_NAME}/partition")

  OLD_DISKID=$(fdisk -l "$ROOT_DEV" | sed -n 's/Disk identifier: 0x\([^ ]*\)/\1/p')

  check_noobs

  ROOT_DEV_SIZE=$(cat "/sys/block/${ROOT_DEV_NAME}/size")
  TARGET_END=$((ROOT_DEV_SIZE - 1))

  PARTITION_TABLE=$(parted -m "$ROOT_DEV" unit s print | tr -d 's')

  LAST_PART_NUM=$(echo "$PARTITION_TABLE" | tail -n 1 | cut -d ":" -f 1)

  ROOT_PART_LINE=$(echo "$PARTITION_TABLE" | grep -e "^${ROOT_PART_NUM}:")
  ROOT_PART_START=$(echo "$ROOT_PART_LINE" | cut -d ":" -f 2)
  ROOT_PART_END=$(echo "$ROOT_PART_LINE" | cut -d ":" -f 3)

  if [ "$NOOBS" = "1" ]; then
    EXT_PART_LINE=$(echo "$PARTITION_TABLE" | grep ":::;" | head -n 1)
    EXT_PART_NUM=$(echo "$EXT_PART_LINE" | cut -d ":" -f 1)
    EXT_PART_START=$(echo "$EXT_PART_LINE" | cut -d ":" -f 2)
    EXT_PART_END=$(echo "$EXT_PART_LINE" | cut -d ":" -f 3)
  fi
}

fix_partuuid() {
  DISKID="$(fdisk -l "$ROOT_DEV" | sed -n 's/Disk identifier: 0x\([^ ]*\)/\1/p')"

  sed -i "s/${OLD_DISKID}/${DISKID}/g" /etc/fstab
  sed -i "s/${OLD_DISKID}/${DISKID}/" /boot/cmdline.txt
}

check_variables () {
  if [ "$NOOBS" = "1" ]; then
    if [ "$EXT_PART_NUM" -gt 4 ] || \
       [ "$EXT_PART_START" -gt "$ROOT_PART_START" ] || \
       [ "$EXT_PART_END" -lt "$ROOT_PART_END" ]; then
      FAIL_REASON="Unsupported extended partition"
      return 1
    fi
  fi

  if [ "$BOOT_DEV_NAME" != "$ROOT_DEV_NAME" ]; then
      FAIL_REASON="Boot and root partitions are on different devices"
      return 1
  fi

  if [ "$ROOT_PART_NUM" -ne "$LAST_PART_NUM" ]; then
    FAIL_REASON="Root partition should be last partition"
    return 1
  fi

  if [ "$ROOT_PART_END" -gt "$TARGET_END" ]; then
    FAIL_REASON="Root partition runs past the end of device"
    return 1
  fi

  if [ ! -b "$ROOT_DEV" ] || [ ! -b "$ROOT_PART_DEV" ] || [ ! -b "$BOOT_PART_DEV" ] ; then
    FAIL_REASON="Could not determine partitions"
    return 1
  fi
}

check_kernel () {
  local MAJOR=$(uname -r | cut -f1 -d.)
  local MINOR=$(uname -r | cut -f2 -d.)
  if [ "$MAJOR" -eq "4" ] && [ "$MINOR" -lt "9" ]; then
    return 0
  fi
  if [ "$MAJOR" -lt "4" ]; then
    return 0
  fi
  NEW_KERNEL=1
}

main () {
  get_variables

  if ! check_variables; then
    return 1
  fi

  check_kernel

  if [ "$NOOBS" = "1" ] && [ "$NEW_KERNEL" != "1" ]; then
    BCM_MODULE=$(grep -e "^Hardware" /proc/cpuinfo | cut -d ":" -f 2 | tr -d " " | tr '[:upper:]' '[:lower:]')
    if ! modprobe "$BCM_MODULE"; then
      FAIL_REASON="Couldn't load BCM module $BCM_MODULE"
      return 1
    fi
  fi

  if [ "$ROOT_PART_END" -eq "$TARGET_END" ]; then
    reboot_pi
  fi

  if [ "$NOOBS" = "1" ]; then
    if ! parted -m "$ROOT_DEV" u s resizepart "$EXT_PART_NUM" yes "$TARGET_END"; then
      FAIL_REASON="Extended partition resize failed"
      return 1
    fi
  fi

  if ! parted -m "$ROOT_DEV" u s resizepart "$ROOT_PART_NUM" "$TARGET_END"; then
    FAIL_REASON="Root partition resize failed"
    return 1
  fi

  partprobe "$ROOT_DEV"
  fix_partuuid

  return 0
}

mount -t proc proc /proc
mount -t sysfs sys /sys
mount -t tmpfs tmp /run
mkdir -p /run/systemd

mount /boot
mount / -o remount,rw

sed -i 's| init=/usr/lib/raspi-config/init_resize\.sh||' /boot/cmdline.txt
sed -i 's| sdhci\.debug_quirks2=4||' /boot/cmdline.txt

if ! grep -q splash /boot/cmdline.txt; then
  sed -i "s/ quiet//g" /boot/cmdline.txt
fi
sync

echo 1 > /proc/sys/kernel/sysrq

if ! check_commands; then
  reboot_pi
fi

if main; then
  whiptail --infobox "Resized root filesystem. Rebooting in 5 seconds..." 20 60
  sleep 5
else
  sleep 5
  whiptail --msgbox "Could not expand filesystem, please try raspi-config or rc_gui.\n${FAIL_REASON}" 20 60
fi

reboot_pi