Day 5 – Disk Management & LVM in Linux

📌 Introduction

In Day 5 of our Linux Administration series, we focus on one of the most important responsibilities of a system administrator — Disk Management.

We will cover:

• File system types

• Essential disk commands

• Traditional partitioning using fdisk

• Modern disk management using LVM

• Creating, extending & removing LVM

• Migrating data using pvmove

• Resizing disk in AWS Cloud

Let’s begin 🚀

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📂 1️⃣ Types of File Systems in Linux

Common file systems used in enterprise environments:

File System	Usage
ext4	Default in many Linux systems
xfs	Default in RHEL / Rocky
vfat	USB drives
nfs	Network storage
cifs	Windows share

Check filesystem type:

lsblk -f

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📊 2️⃣ Essential Disk Management Commands

🔹 Check Disk Space

df -h

🔹 Check Directory Size

du -h

🔹 Identify Large Directories

du -h --max-depth=1 | sort -hr

🔹 Check Inode Usage

df -i

🔹 List Block Devices

lsblk

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🧱 3️⃣ Traditional Partitioning – fdisk

Before LVM, Linux used fdisk for partition management.

Create a Partition:

fdisk /dev/sdb

Steps:

• Press n → new partition

• Press p → primary

• Accept defaults

• Press w → write changes

Create filesystem:

mkfs.ext4 /dev/sdb1

Mount:

mount /dev/sdb1 /mnt

⚠ Limitation: Cannot easily resize partitions.

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🚀 4️⃣ What is LVM?

LVM (Logical Volume Manager) provides:

✔ Flexible disk management
✔ Easy resizing
✔ Storage pooling
✔ Snapshot support
✔ Data migration

LVM Architecture

Physical Volume (PV)
        ↓
Volume Group (VG)
        ↓
Logical Volume (LV)
        ↓
Filesystem
        ↓
Mount Point

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🛠 5️⃣ Create LVM Step-by-Step

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🔹 Step 1: Create Physical Volume

pvcreate /dev/sdb
pvdisplay

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🔹 Step 2: Create Volume Group

vgcreate vg01 /dev/sdb
vgdisplay vg01

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🔹 Step 3: Create Logical Volumes

lvcreate -L 1G -n lv_ext4 vg01
lvcreate -L 1G -n lv_xfs vg01

Check:

lvdisplay

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🔹 Step 4: Create File System

mkfs.ext4 /dev/vg01/lv_ext4
mkfs.xfs /dev/vg01/lv_xfs

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🔹 Step 5: Mount Logical Volumes

mkdir /lvm_ext4
mkdir /lvm_xfs

mount /dev/vg01/lv_ext4 /lvm_ext4
mount /dev/vg01/lv_xfs /lvm_xfs

Verify:

df -h

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🔹 Step 6: Make Persistent (fstab)

Edit:

vi /etc/fstab

Add:

/dev/vg01/lv_ext4 /lvm_ext4 ext4 defaults 0 0
/dev/vg01/lv_xfs  /lvm_xfs  xfs  defaults 0 0

Test:

mount -a

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📈 6️⃣ Extend LVM Volume

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Add New Disk

pvcreate /dev/sdc
vgextend vg01 /dev/sdc

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Extend Logical Volume

lvextend -L +1G /dev/vg01/lv_ext4

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Resize Filesystem

For ext4:

resize2fs /dev/vg01/lv_ext4

For XFS:

xfs_growfs /lvm_xfs

Check:

df -h

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🔄 7️⃣ Migrate Data Using pvmove

Used when replacing old disk.

pvcreate /dev/sdd
vgextend vg01 /dev/sdd
pvmove /dev/sdc /dev/sdd
vgreduce vg01 /dev/sdc
pvremove /dev/sdc

Monitor migration:

lvs -a -o +devices

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🗑 8️⃣ Decommission LVM

umount /lvm_ext4
lvremove /dev/vg01/lv_ext4
vgremove vg01
pvremove /dev/sdb

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☁ 9️⃣ Resize Disk in AWS

Steps:

1. Increase EBS volume from AWS console

2. Check disk:

lsblk

3. Extend partition:

growpart /dev/xvda 1

4. Resize filesystem:

For ext4:

resize2fs /dev/xvda1

For XFS:

xfs_growfs -d /

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🔥 Troubleshooting Section

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❌ Mount Fails

blkid
cat /etc/fstab

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❌ LV Remove Fails (Device Busy)

lsof | grep mountpoint

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❌ Filesystem Not Expanding

Check:

lsblk
lvdisplay

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🎤 Interview Questions

1. Difference between fdisk and LVM?

2. Can XFS be reduced?

3. What is PE size?

4. What happens if PV disk fails?

5. How to check which disk LV uses?

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📌 Conclusion

Today we learned:

✔ Disk management basics
✔ fdisk partitioning
✔ LVM architecture
✔ Create, extend & remove LVM
✔ Data migration
✔ Cloud disk resizing

LVM is the backbone of modern Linux storage management in enterprise environments.