linux extend disk partition script

resize_disk.sh

#!/usr/bin/env bash
# Exit immediately if a command exits with a non-zero status.
set -e

# Find the device containing the root filesystem (e.g., /dev/sda3 or /dev/mapper/vg-root)
ROOT_FS_DEVICE=$(findmnt -n -o SOURCE /)

# Check if ROOT_FS_DEVICE was found
if [ -z "$ROOT_FS_DEVICE" ]; then
    echo "Error: Could not determine root filesystem device."
    exit 1
fi

# Determine if the root filesystem is on an LVM Logical Volume
IS_LVM=false
if [[ "$ROOT_FS_DEVICE" == /dev/mapper/* || "$ROOT_FS_DEVICE" == /dev/*/vg-* ]]; then
    # Check if it's truly an LVM LV by querying lvs
    if lvs "$ROOT_FS_DEVICE" &>/dev/null; then
        IS_LVM=true
    fi
fi

ROOT_PARTITION_TO_GROW="" # This will be the /dev/sdXN partition to grow
ROOT_DISK_NAME=""         # The parent disk name (e.g., sda)
ROOT_PARTITION_NUM=""     # The partition number (e.g., 3)

if $IS_LVM; then
    echo "Root filesystem is on an LVM Logical Volume: ${ROOT_FS_DEVICE}"
    # Get the Physical Volume (PV) backing the root Logical Volume (LV)
    # Example: /dev/mapper/vg-root -> /dev/sda3
    ROOT_PV_PATH=$(lvs -o pv_name --noheadings "$ROOT_FS_DEVICE" 2>/dev/null | xargs)

    if [ -z "$ROOT_PV_PATH" ]; then
        echo "Error: Could not determine Physical Volume for ${ROOT_FS_DEVICE}."
        exit 1
    fi
    echo "Root LV's Physical Volume: ${ROOT_PV_PATH}"

    # The partition to grow is the PV itself
    ROOT_PARTITION_TO_GROW="$ROOT_PV_PATH"
else
    echo "Root filesystem is directly on a partition: ${ROOT_FS_DEVICE}"
    # The partition to grow is the root filesystem device itself
    ROOT_PARTITION_TO_GROW="$ROOT_FS_DEVICE"
fi

# Extract the parent disk name (e.g., sda) and partition number (e.g., 3)
# from the partition device using lsblk
read -r ROOT_DISK_NAME ROOT_PARTITION_NUM <<< $(lsblk -no PKNAME,PARTNO "${ROOT_PARTITION_TO_GROW}")

# Check if disk name and partition number were extracted
if [ -z "$ROOT_DISK_NAME" ] || [ -z "$ROOT_PARTITION_NUM" ]; then
    echo "Error: Could not extract disk or partition number from ${ROOT_PARTITION_TO_GROW}."
    echo "This script expects the root filesystem (or its underlying PV) to be a standard partition (e.g., /dev/sda3)."
    exit 1
fi

# Construct the full disk device path (e.g., /dev/sda)
ROOT_DISK_DEV="/dev/${ROOT_DISK_NAME}"

echo "Extending root filesystem on ${ROOT_FS_DEVICE}..."
echo "Target partition to grow: ${ROOT_PARTITION_TO_GROW}"
echo "Parent disk: ${ROOT_DISK_DEV}"
echo "Partition number: ${ROOT_PARTITION_NUM}"

# Rescan the disk to pick up potential size changes
# Note: This requires root privileges.
echo "Rescanning disk ${ROOT_DISK_DEV}..."
echo 1 | sudo tee "/sys/block/${ROOT_DISK_NAME}/device/rescan" > /dev/null

# Grow the partition that contains root (or is the PV for root LV)
# Note: This requires root privileges.
echo "Growing partition ${ROOT_PARTITION_TO_GROW}..."
sudo growpart "${ROOT_DISK_DEV}" "${ROOT_PARTITION_NUM}"

if $IS_LVM; then
    # Extend the physical volume on the root partition
    # Note: This requires root privileges.
    echo "Resizing Physical Volume ${ROOT_PV_PATH}..."
    sudo pvresize "${ROOT_PV_PATH}"

    # Extend the logical volume corresponding to the root device
    # Use -r to resize the filesystem automatically after extending the LV
    # Use -l +100%FREE to use all available free space in the volume group
    # Note: This requires root privileges.
    echo "Extending Logical Volume ${ROOT_FS_DEVICE} and resizing filesystem..."
    sudo lvextend -r -l +100%FREE "${ROOT_FS_DEVICE}"
else
    # If not LVM, directly resize the filesystem on the partition
    # Note: This requires root privileges.
    echo "Resizing filesystem on ${ROOT_FS_DEVICE}..."
    FSTYPE=$(findmnt -n -o FSTYPE "$ROOT_FS_DEVICE")
    case "$FSTYPE" in
        ext2|ext3|ext4)
            sudo resize2fs "$ROOT_FS_DEVICE"
            ;;
        xfs)
            sudo xfs_growfs "$ROOT_FS_DEVICE"
            ;;
        *)
            echo "Warning: Unknown filesystem type '$FSTYPE' on ${ROOT_FS_DEVICE}. Manual resize may be needed."
            ;;
    esac
fi

echo "Root filesystem extension complete."