Enlarge disk size inside debian/ubuntu VM

grow-root.sh

#!/usr/bin/env bash
set -euo pipefail

# Simple helper to print info
log()  { echo -e "\e[1;34m[INFO]\e[0m $*"; }
warn() { echo -e "\e[1;33m[WARN]\e[0m $*"; }
err()  { echo -e "\e[1;31m[ERR]\e[0m  $*" >&2; }

if [[ $EUID -ne 0 ]]; then
  err "This script must be run as root."
  exit 1
fi

# Check for required tools
for cmd in lsblk findmnt parted growpart; do
  if ! command -v "$cmd" &>/dev/null; then
    err "Required command '$cmd' not found. Install it and re-run."
    if [[ "$cmd" == "growpart" ]]; then
      echo "  On Ubuntu: apt update && apt install -y cloud-guest-utils"
    fi
    exit 1
  fi
done

# ---- Detect root mount ----
root_src=$(findmnt -n -o SOURCE /)
root_fstype=$(findmnt -n -o FSTYPE /)

log "Root filesystem: $root_src (type: $root_fstype)"

is_lvm=false
if [[ "$root_src" == /dev/mapper/* ]]; then
  is_lvm=true
fi

# ---- Helper to grow a partition to end of disk ----
grow_partition() {
  local part_dev="$1"

  # Underlying disk (e.g. sda for sda3, nvme0n1 for nvme0n1p3)
  local disk_name
  disk_name=$(lsblk -no PKNAME "$part_dev")
  local disk_dev="/dev/${disk_name}"

  # Partition name relative to disk (e.g. sda3 -> 3, nvme0n1p3 -> 3)
  local part_name
  part_name=$(basename "$part_dev")

  # Extract numeric partition index (handle sdX#, vdX#, nvmeXnYp#)
  local part_num
  part_num=$(echo "$part_name" | sed 's/[^0-9]*//g')

  if [[ -z "$part_num" ]]; then
    err "Could not determine partition number for $part_dev"
    exit 1
  fi

  log "Disk device:    $disk_dev"
  log "Partition dev:  $part_dev (partition #$part_num)"

  log "Growing partition $part_dev to fill $disk_dev using growpart..."
  growpart "$disk_dev" "$part_num"

  log "Partition growth completed."
}

# ---- Non-LVM root case ----
resize_plain_root() {
  local part_dev="$1"
  local fstype="$2"

  grow_partition "$part_dev"

  case "$fstype" in
    ext4|ext3)
      log "Resizing ext filesystem on $part_dev with resize2fs..."
      resize2fs "$part_dev"
      ;;
    xfs)
      # xfs_growfs works on the mounted filesystem, use the mountpoint
      if ! command -v xfs_growfs &>/dev/null; then
        err "xfs_growfs not found, install xfsprogs (apt install -y xfsprogs)."
        exit 1
      fi
      log "Resizing XFS filesystem on / with xfs_growfs..."
      xfs_growfs /
      ;;
    *)
      err "Unsupported filesystem type '$fstype' for plain root. Aborting."
      exit 1
      ;;
  esac

  log "Plain root filesystem resize completed."
}

# ---- LVM root case ----
resize_lvm_root() {
  local lv_dev="$1"

  # Find the PV backing this LV (assume single PV)
  local pv_dev
  pv_dev=$(pvs --noheadings -o pv_name "$lv_dev" 2>/dev/null | awk '{$1=$1};1' | head -n1 || true)

  if [[ -z "$pv_dev" ]]; then
    err "Could not determine PV for LV $lv_dev. Is LVM set up normally?"
    exit 1
  fi

  log "Detected PV for root LV: $pv_dev"

  # Grow the underlying partition
  grow_partition "$pv_dev"

  # Resize PV to take new space
  log "Resizing PV $pv_dev with pvresize..."
  pvresize "$pv_dev"

  # Extend LV to use all free space, and grow filesystem in-place (-r)
  log "Extending LV $lv_dev to use all free space (lvextend -r -l +100%FREE)..."
  lvextend -r -l +100%FREE "$lv_dev"

  log "LVM root resize completed."
}

# ---- Main logic ----
if [[ "$is_lvm" == false ]]; then
  log "Detected non-LVM root."
  if [[ "$root_src" != /dev/* ]]; then
    err "Unexpected root source: $root_src (not a /dev device). Aborting."
    exit 1
  fi
  resize_plain_root "$root_src" "$root_fstype"
else
  log "Detected LVM root: $root_src"
  if ! command -v pvs &>/dev/null || ! command -v lvextend &>/dev/null; then
    err "LVM tools not found. Install lvm2 (apt install -y lvm2) and retry."
    exit 1
  fi
  resize_lvm_root "$root_src"
fi

log "All done. Current block devices:"
lsblk