Master Linux LVM: Step‑by‑Step Guide to Create, Resize, and Snapshot Logical Volumes

LVM (Logical Volume Manager) is a Linux storage subsystem that aggregates physical disks into a flexible pool, allowing dynamic resizing of partitions and better utilization of disk space.

Key LVM Components

Physical Volume (PV) : a disk or partition that becomes a physical storage unit.

Volume Group (VG) : a collection of one or more PVs, treated as a single large disk.

Logical Volume (LV) : a partition carved out of a VG; it can be formatted and used to store data.

Physical Extent (PE) : the smallest allocatable unit inside a VG (default 4 MiB, configurable).

Creating and Removing Physical Volumes

# List available disks
ll /dev/sd[b-z]
# Create PVs on two disks
pvcreate /dev/sdb /dev/sdc
# Remove a PV (example)
pvremove /dev/sdc
# Verify PVs
pvs

Creating a Volume Group

# Show current PVs
pvs
# Create a VG named my_vg using the two PVs, with 4 MiB PE size
vgcreate -s 4M my_vg /dev/sdb /dev/sdc
# List VGs
vgs

Adding a New PV to an Existing VG

# Extend the VG with an additional disk
vgextend my_vg /dev/sdd
# Verify the addition
pvs

Removing a Single PV from a VG

# Remove /dev/sdd from my_vg
vgreduce my_vg /dev/sdd
# Verify the removal
pvs

Removing an Entire VG

# List VGs
vgs
# Delete the VG named my_vg
vgremove my_vg
# Confirm removal
vgs

Removing an Empty VG

# Remove a VG that has no allocated space
vgreduce -a my_vg
# Verify the result
vgs

Creating a Logical Volume

# Create a 10 GiB LV named my_lv in my_vg
lvcreate -L 10G -n my_lv my_vg
# List LVs to confirm
lvs

Formatting and Mounting the LV

# Create a mount point
mkdir /LVM
# Format the LV with ext4
mkfs.ext4 /dev/my_vg/my_lv
# Mount it
mount /dev/my_vg/my_lv /LVM/

Extending the LV (Resize Up)

# Check current size
df -h
# Add 5 GiB to the LV
lvextend -L +5G /dev/my_vg/my_lv
# Resize the filesystem
resize2fs -f /dev/my_vg/my_lv
# Verify new size
df -h

Shrinking the LV (Resize Down)

# Unmount the LV
umount /dev/my_vg/my_lv
# Check filesystem integrity
e2fsck -f /dev/my_vg/my_lv
# Reduce filesystem to 10 GiB
resize2fs -f /dev/my_vg/my_lv 10G
# Reduce the LV itself
lvreduce -L 10G /dev/my_vg/my_lv
# Remount and verify
mount /dev/my_vg/my_lv /LVM/
df -h

Creating a Snapshot

# Take a 200 MiB snapshot of my_lv
lvcreate -s -n mylv_back -L 200M /dev/my_vg/my_lv
# List LVs to see the snapshot
lvs

Restoring from a Snapshot

# Simulate data loss, then mount the snapshot
mkdir /back
mount /dev/my_vg/mylv_back /back/
# Copy data back to the original LV
cp -a /back/* /LVM/
# (Optional) Unmount and clean up
umount /back

Original source: https://www.cnblogs.com/LyShark/p/10167313.html