Extending LVM Logical Volume (LV) in Linux – Runbook

Extending LVM Logical Volume (LV) in Linux – Runbook - Printable Version

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Extending LVM Logical Volume (LV) in Linux – Runbook - Kalyani - 04-22-2026

Purpose
Extend disk space on a Linux system using LVM without downtime.

Applies to
Systems using LVM (Logical Volume Manager)

Problem

Filesystem (e.g. /, /var) is running out of space and needs to be extended.

Step 1 — Check Current Disk Usage

Code:
df -h

Output:

Code:
/dev/mapper/rootvg-varlv    14G  13G  1.4G  91% /var

Outcome:

Identify which mount point is full (e.g /var)
This determines which LV needs extension

Step 2 — Verify LVM Setup (Build Context for Extension)

1. Map LV to Mount Point

Code:
lsblk

Output :

Code:
NAME              MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS

sda                8:0    0  256G  0 disk

├─sda4              8:4    0 63.3G  0 part

  ├─rootvg-varlv  253:3    0  14G  0 lvm  /var

└─sda5              8:5    0  100G  0 part

  ├─rootvg-varlv  253:3    0  14G  0 lvm  /var

Insight:

Identifies which LV is mounted where
Confirms LVM usage (TYPE = lvm)

2. Identify Target LV

Code:
lvs -o lv_name,vg_name,lv_path

Output:

Code:
LV    VG    Path

varlv  rootvg /dev/rootvg/varlv

Insight:

Confirms exact LV name to extend (e.g varlv)
Provides correct device path required for lvextend (e.g /dev/rootvg/varlv)

3. Check Available Space in VG

Code:
vgs

Output:

Code:
VG    #PV #LV #SN Attr  VSize    VFree

rootvg  2  5  0 wz--n- <163.31g 316.00m

Insight:

Determines if extension is possible

Interpretation:

VFree > 0
→ Extend directly
VFree = 0
→ Add disk first

4. Check Underlying Disks

Code:
pvs

Code:
PV        VG    Fmt  Attr PSize    PFree

/dev/sda4  rootvg lvm2 a--  63.31g    0

/dev/sda5  rootvg lvm2 a--  <100.00g 316.00m

Insight:

Shows disks backing the VG
Confirms whether storage is already fully utilized

Step 2 Outcome (What we now know)

Which LV to extend (varlv)
Its mount point (/var) and exact path (/dev/rootvg/varlv)
Whether free space exists in VG
Which disks are backing LVM

Decision Point

Case A: VG has free space
→ Extend LV directly

Case B: No free space
→ Add disk / extend storage first

Case A — Extend LV (VG has free space)

Step 3 — Extend Logical Volume

Code:
lvextend -L +316M /dev/rootvg/varlv

-L → size in GB/MB

OR use all free space:

Code:
lvextend -l +100%FREE /dev/rootvg/varlv

-l → extents / percentage

Outcome:

Code:
Size of logical volume rootvg/varlv changed from 14.00 GiB (3584 extents) to <14.31 GiB (3663 extents).

Logical volume rootvg/varlv successfully resized.

LV size increases
Filesystem unchanged (IMPORTANT)

Step 4 — Resize Filesystem

Check filesystem:

Code:
lsblk -f

For ext4:

Code:
resize2fs /dev/rootvg/varlv

For xfs:

Code:
xfs_growfs /var

Outcome:

Filesystem expands to use new space

Step 5 — Verify

Code:
df -h

Case B — No Free Space in VG

Step 3 — Add New Disk (Cloud / VM level)

Add a new disk from your cloud provider / hypervisor (e.g. AWS, Azure, VMware)
Example: New disk appears as /dev/sdb
Verify Disk is Added

Code:
lsblk
New disk should be visible (e.g. /dev/sdb)

Step 4 — Create PV

Code:
pvcreate /dev/sdb

Step 5 — Extend VG

Code:
vgextend rootvg /dev/sdb

Step 6 — Extend LV

Code:
lvextend -l +100%FREE /dev/rootvg/varlv

Step 7 — Resize Filesystem

Code:
xfs_growfs /var

# OR

Code:
resize2fs /dev/rootvg/varlv

Step 8 — Verify

Code:
df -h

Additional Note — Expanding Existing Disk

If the same disk is increased in size (no new disk added):

Code:
growpart /dev/sda 4

Code:
pvresize /dev/sda4

Outcome:

growpart → expands the partition
pvresize → makes new space available to LVM

You can now proceed with lvextend

Common Mistakes

Extending LV but not resizing filesystem
Using wrong filesystem command (resize2fs vs xfs_growfs)
Not checking vgs before starting
Using wrong device path
Confusing disk (/dev/sdb) with LV (/dev/rootvg/varlv)

Key Concepts and Takeaways

PV (Physical Volume) → Disk (/dev/sda4)
VG (Volume Group) → Storage pool (rootvg)
LV (Logical Volume) → Usable volume (/var)

Flow:
Disk → PV → VG → LV → Filesystem

Extension = LV resize + filesystem resize
vgs decides your approach (direct vs add disk)
LVM allows online resizing (no downtime)

Precautions

Take backup before changes
Double-check device names
Run carefully on production