How to Extend a Disk on Linux: LVM and Ext4 Step by Step

You upgraded your VDS disk in the KavesNET panel, but df -h still shows the old size? The disk grew but the partition + filesystem didn’t. This guide shows how to safely extend LVM and standard ext4 partitions.

First: take a backup

Disk operations are risky. Before continuing, always take a snapshot or at least back up critical data. See our 3-2-1 backup post.

Inspect current state

# Disk size
lsblk

# Mounted area
df -h

# Partition table
sudo fdisk -l /dev/sda

Typical: /dev/sda is 100 GB but /dev/sda1 (root) is still 50 GB.

Method 1: extend with LVM (recommended)

KavesNET servers typically ship Ubuntu/AlmaLinux with LVM. LVM’s biggest win: non-disruptive online resize.

1. Grow the Physical Volume

# If /dev/sda3 is your LVM partition
sudo pvresize /dev/sda3
sudo pvs  # you should see PFree

2. Grow the Logical Volume

sudo lvs  # list existing LVs
sudo lvextend -l +100%FREE /dev/ubuntu-vg/ubuntu-lv

+100%FREE → use all free space.

3. Grow the filesystem

Ext4:

sudo resize2fs /dev/ubuntu-vg/ubuntu-lv

XFS:

sudo xfs_growfs /

4. Verify

df -h

New size should appear. No reboot needed — done live.

Method 2: without LVM (cloud-init / growpart)

If you don’t have LVM, grow the partition first.

1. Extend partition with growpart

sudo apt install cloud-guest-utils -y  # Ubuntu
sudo dnf install cloud-utils-growpart -y  # AlmaLinux

sudo growpart /dev/sda 1

2. Grow filesystem

# ext4
sudo resize2fs /dev/sda1

# xfs
sudo xfs_growfs /

Method 3: parted manual (legacy)

sudo parted /dev/sda
(parted) print  # show current partitions
(parted) resizepart 1 100%  # extend partition 1 to end of disk
(parted) quit

sudo resize2fs /dev/sda1

⚠️ A power/network failure mid-resize corrupts the filesystem — UPS-backed server or snapshot is essential.

Common errors

• “Couldn’t find valid filesystem superblock”: Partition table corrupted — restore from backup
• “Partition not aligned”: Check with parted’s align-check optimal 1
• pvresize extends by 0: Partition not extended first → run growpart
• Read-only filesystem: Filesystem error → sudo fsck /dev/sda1 (unmount first)

Adding a new disk (alternative)

Instead of growing the existing disk, you can add a new one and mount it:

# New disk (e.g. /dev/sdb) should appear
lsblk

# Create partition and filesystem
sudo parted /dev/sdb mklabel gpt mkpart primary ext4 0% 100%
sudo mkfs.ext4 /dev/sdb1

# Mount
sudo mkdir /mnt/data
sudo mount /dev/sdb1 /mnt/data

# Auto-mount via /etc/fstab
echo "/dev/sdb1 /mnt/data ext4 defaults 0 2" | sudo tee -a /etc/fstab

Conclusion

On LVM-enabled servers, disk extension is a 3-command job: pvresize → lvextend → resize2fs. Watch df -h regularly and grow before you fill up.

In KavesNET panel, disk-growth request is auto-completed in ~5 minutes. Then run these commands to grow the filesystem.

Related: Server Backups · SSH Connection