Linux Disk Management LVM Guide

Physical Disks:  /dev/sda   /dev/sdb   /dev/sdc
                    ↓          ↓          ↓
Physical Volumes: PV1        PV2        PV3
                    ↓          ↓          ↓
Volume Group:    ←─── vg_data ────────────→
                    ↓          ↓
Logical Volumes: lv_app     lv_db
                    ↓          ↓
Filesystems:     /opt/app   /var/lib/postgres

# Partition the disk (or use whole disk)
sudo pvcreate /dev/sdb
sudo pvcreate /dev/sdc

# Verify
sudo pvs
sudo pvdisplay

sudo vgcreate vg_data /dev/sdb /dev/sdc

# Verify
sudo vgs
sudo vgdisplay vg_data

# Fixed size
sudo lvcreate -L 50G -n lv_app vg_data

# Percentage of free space
sudo lvcreate -l 80%FREE -n lv_db vg_data

# All remaining space
sudo lvcreate -l 100%FREE -n lv_logs vg_data

# Verify
sudo lvs
sudo lvdisplay

sudo mkfs.ext4 /dev/vg_data/lv_app
sudo mkfs.xfs /dev/vg_data/lv_db

sudo mkdir -p /opt/app /var/lib/postgres

sudo mount /dev/vg_data/lv_app /opt/app
sudo mount /dev/vg_data/lv_db /var/lib/postgres

# Persistent mount
echo '/dev/vg_data/lv_app /opt/app ext4 defaults 0 2' | sudo tee -a /etc/fstab
echo '/dev/vg_data/lv_db /var/lib/postgres xfs defaults 0 2' | sudo tee -a /etc/fstab

# Add 20GB
sudo lvextend -L +20G /dev/vg_data/lv_app

# Extend to specific size
sudo lvextend -L 100G /dev/vg_data/lv_app

# Use all free space
sudo lvextend -l +100%FREE /dev/vg_data/lv_app

# Resize filesystem to match
sudo resize2fs /dev/vg_data/lv_app    # ext4
sudo xfs_growfs /opt/app               # xfs (mounted path)

# Or do both at once
sudo lvextend -L +20G --resizefs /dev/vg_data/lv_app

# Add physical volume
sudo pvcreate /dev/sdd

# Extend volume group
sudo vgextend vg_data /dev/sdd

# Now extend logical volumes with the new space
sudo lvextend -l +100%FREE --resizefs /dev/vg_data/lv_app

# Must unmount first!
sudo umount /opt/app

# Check filesystem
sudo e2fsck -f /dev/vg_data/lv_app

# Shrink filesystem first
sudo resize2fs /dev/vg_data/lv_app 30G

# Then shrink LV
sudo lvreduce -L 30G /dev/vg_data/lv_app

# Remount
sudo mount /dev/vg_data/lv_app /opt/app

# Create snapshot (needs free space in VG)
sudo lvcreate -L 5G -s -n lv_app_snap /dev/vg_data/lv_app

# Mount snapshot (read-only)
sudo mkdir /mnt/snap
sudo mount -o ro /dev/vg_data/lv_app_snap /mnt/snap

# Backup from snapshot
tar czf /backup/app-$(date +%Y%m%d).tar.gz /mnt/snap/

# Remove snapshot
sudo umount /mnt/snap
sudo lvremove /dev/vg_data/lv_app_snap

# Merge snapshot back (restores to snapshot point)
sudo umount /opt/app
sudo lvconvert --merge /dev/vg_data/lv_app_snap
sudo mount /dev/vg_data/lv_app /opt/app

# Overview
sudo pvs && sudo vgs && sudo lvs

# Detailed info
sudo pvdisplay
sudo vgdisplay
sudo lvdisplay

# Free space
sudo vgs -o +vg_free

# Disk usage
df -h

# Physical extent map
sudo pvs -o +pv_used

# List disks
lsblk
fdisk -l

# Partition
sudo fdisk /dev/sdb
# or
sudo parted /dev/sdb

# Format
sudo mkfs.ext4 /dev/sdb1
sudo mkfs.xfs /dev/sdb1

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

# Check filesystem
sudo fsck /dev/sdb1        # ext4 (must be unmounted)
sudo xfs_repair /dev/sdb1  # xfs

# Disk health
sudo smartctl -a /dev/sda