Resize Linux Root Partition on a Live System Without Rebooting

Why Resize Root Without Reboot?

Running out of space on your root partition and can’t afford downtime? On modern Linux systems, it’s totally possible to safely resize your root partition while the system is live — no reboot required.

This guide is tailored for Debian-based systems and uses native tools like parted, resize2fs, and partprobe to help you make use of unused disk space without interruption.

Prerequisites

Before you begin, make sure the following are in place:

• The disk has unallocated space.
• You have root or sudo privileges.
• Installed tools: parted, resize2fs or xfs_growfs, partprobe, lsblk, df, kpartx (optional).
• Full system backup or snapshot (mandatory!).

Warning: Always back up your data. Resizing partitions carries risk!

Step 1: Inspect the Current Partition Layout

Run the following commands to understand your current setup:

lsblk
lsblk -f (for FSTYPE or df -T)
fdisk -l <disk>

Sample Outputs:

NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
vda    252:0    0   40G  0 disk 
├─vda1 252:1    0    1M  0 part 
└─vda2 252:2    0   40G  0 part /


root@ubuntu-jammy-server:~# df -T
Filesystem     Type  1K-blocks     Used Available Use% Mounted on
tmpfs          tmpfs    201108     1112    199996   1% /run
/dev/vda2      ext4   41102636 16290900  22908176  42% /
tmpfs          tmpfs   1005536        0   1005536   0% /dev/shm
tmpfs          tmpfs      5120        0      5120   0% /run/lock
tmpfs          tmpfs    201104        4    201100   1% /run/user/1000

You can extend Your disk space now and check again to verify disk size increased

You can see now my vda disk +5 GB increased but my root partition is still 40GB I can extend 5GB now.

Step 2: Back Up Your System

Back up everything before proceeding.

Option 1: Snapshot (if supported)

# LVM
lvcreate --snapshot --name root_snap /dev/mapper/ubuntu--vg-root --size 5G

Option 2: Rsync

rsync -aAXv / /mnt/backup/

Step 3: Resize the Partition

Start parted

sudo parted /dev/XXX

Show Current Layout

(parted) print

Resize Partition 2 (/ is partition 2 in my system)

(parted) resizepart 2 100%

resizepart is available in parted 3.0+. If you see resize has been removed, you’re using an outdated or incompatible version.

Confirm Changes

(parted) print
(parted) quit

Step 4: Inform the Kernel

Let the kernel know the partition has changed:

sudo partprobe

If nothing is returned — that’s good. It means no errors.

Optional for Device Mapper Setups

sudo kpartx -u /dev/sda

Step 5: Resize the Filesystem

Now that the partition is larger, expand the actual filesystem.

For ext4:

sudo resize2fs /dev/XXXX

For xfs:

sudo xfs_growfs /

xfs_growfs can only expand a mounted XFS filesystem, which makes it ideal for root partitions.

Step 6: Verify Everything Worked

Check New Disk Usage:

df -h /
lsblk

You should now see /dev/XXXX showing a size close to your total disk capacity.

Optional: Add a Swap Partition

If you have extra space and no swap, you can add one now.

Create New Swap Partition

sudo parted /dev/XXXX mkpart primary linux-swap XXGB XXGB

Format and Activate Swap

sudo mkswap /dev/XXXX
sudo swapon /dev/XXXX

Make Swap Persistent

echo '/dev/XXXX none swap sw 0 0' | sudo tee -a /etc/fstab

Confirm Swap Is Enabled

swapon --show
free -h

Done — No Reboot Needed!

You just resized the root partition of a live system without taking it offline.

Final Check:

uptime

The uptime confirms the system remained live the whole time.

Further Reading

• man parted
• man resize2fs
• Debian Partitioning Guide

Thanks for reading!

—

Guneycan Sanli

Guneycan Sanli

A person who like learning, music, travelling and sports.

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