LVM on a server: resizing a disk with no downtime

What LVM is and why you'd resize a disk with no downtime

LVM (Logical Volume Manager) is an abstraction layer between physical disks and the file system. Instead of mounting a partition directly, LVM combines one or more disks into a volume group, then carves logical volumes of any size out of it. The main benefit for a VDS: after the hosting provider increases the disk size in the control panel, you extend the logical volume and the file system on the fly, without stopping services or rebooting.

Without LVM, growing a partition usually requires stopping services, recreating the partition table, or moving data. With LVM it's a few commands on a live system.

Checking the current LVM configuration

Before resizing, check what the current structure looks like:

lsblk
pvs
vgs
lvs

pvs shows physical volumes, vgs shows volume groups with their total and free size, and lvs shows logical volumes with their mount points. The lsblk command checks the new disk size at the block device level after resizing it in the hosting panel.

Step 1: growing the disk at the system level

After the disk is resized in the hosting provider's panel (with ZevsHost.net this happens in the client panel without rebooting the VDS), the kernel gets notified about the change:

echo 1 > /sys/class/block/sda/device/rescan
partprobe /dev/sda
lsblk

When using a partition (for example, /dev/sda3) that contains LVM, extend the partition with growpart:

apt install -y cloud-guest-utils
growpart /dev/sda 3

After that, lsblk shows the increased size of the /dev/sda3 partition.

Step 2: extending the physical volume and logical volume

LVM gets a signal that the physical volume has grown:

pvresize /dev/sda3
vgs

The VFree field in the vgs output shows the new free space in the volume group. Next, extend the logical volume — using all available space (-l +100%FREE) or a specific size:

lvextend -l +100%FREE /dev/mapper/vgname-root

Check the logical volume's name with lvs — it varies depending on the distribution and how the VDS was created.

Step 3: extending the file system

Extending the logical volume does not automatically change the file system size — it needs a separate command, depending on the file system type:

Both commands run on a mounted, live file system — no downtime is required. Check the result afterward:

df -h /

Common mistakes when resizing LVM

The most common problem is skipping the growpart or partprobe step: then pvresize sees no new space, because the partition table entry is still the old size. The second mistake is mixing up device names: lvextend and resize2fs must point to the same logical volume, visible in lvs under the LV Path column. When free space still hasn't appeared after growing the disk, start diagnostics over with the article on finding what's taking up disk space — the space might already be there, but someone forgot to extend the file system.

Summary: a checklist for resizing an LVM disk

• Grow the disk in the hosting panel, then run partprobe and, if needed, growpart.
• Check the structure: pvs, vgs, lvs.
• Extend the physical volume: pvresize /dev/sdaN.
• Extend the logical volume: lvextend -l +100%FREE /dev/mapper/name.
• Extend the file system: resize2fs for ext4 or xfs_growfs for xfs.
• Check the result with df -h and set up VDS resource monitoring to catch the next time the disk fills up.