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

LVM (Logical Volume Manager) is a Linux mechanism that aggregates physical disks into a single storage pool, allowing dynamic resizing of volumes for better utilization.

Physical Volume (PV) : a disk or partition converted into a physical volume.

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

Logical Volume (LV) : a partition within a VG that can be formatted and store data.

Physical Extent (PE) : the smallest allocatable unit in a VG, default 4 MB but configurable.

Creating/Removing Physical Volumes (PV)

# ll /dev/sd[b-z]
brw-rw---- 1 root disk 8,16 Sep 21 22:04 /dev/sdb
brw-rw---- 1 root disk 8,32 Sep 21 22:04 /dev/sdc
# pvcreate /dev/sdb /dev/sdc
# pvremove /dev/sdc
# pvs
PV         VG     Fmt  Attr PSize   PFree
/dev/sda2  centos lvm2 a--  <9.00g   0
/dev/sdb          lvm2 ---  10.00g 10.00g

Creating a Volume Group (VG)

# vgcreate -s [PE size] [VG name] /dev/sdb /dev/sdc
# vgs
VG       #PV #LV #SN Attr   VSize   VFree
centos   1   2   0  wz--n- <9.00g   0
my_vg    2   0   0  wz--n- 19.99g 19.99g

Adding a New PV to a VG

# vgextend my_vg /dev/sdd
# pvs
PV         VG     Fmt  Attr PSize   PFree
/dev/sda2  centos lvm2 a--  <9.00g   0
/dev/sdb   my_vg  lvm2 a--  <10.00g <10.00g
/dev/sdc   my_vg  lvm2 a--  <10.00g <10.00g
/dev/sdd   my_vg  lvm2 a--  <10.00g <10.00g

Removing a Single PV from a VG

# vgreduce my_vg /dev/sdd
# pvs
PV         VG     Fmt  Attr PSize   PFree
/dev/sda2  centos lvm2 a--  <9.00g   0
/dev/sdb   my_vg  lvm2 a--  <10.00g <10.00g
/dev/sdc   my_vg  lvm2 a--  <10.00g <10.00g
/dev/sdd          lvm2 ---  10.00g 10.00g

Removing an Entire VG

# vgremove my_vg
Volume group "my_vg" successfully removed

Removing an Empty VG # vgreduce -a my_vg Creating a Logical Volume (LV)

# lvcreate -L 10G -n my_lv my_vg
# lvs
LV      VG     Attr       LSize
root    centos -wi-ao---- <8.00g
swap    centos -wi-ao---- 1.00g
my_lv   my_vg  -wi-a----- 10.00g

Formatting and Mounting the LV

# mkdir /LVM
# mkfs.ext4 /dev/my_vg/my_lv
# mount /dev/my_vg/my_lv /LVM/

Extending LV Capacity

# lvextend -L +5G /dev/my_vg/my_lv
# resize2fs -f /dev/my_vg/my_lv

Reducing LV Capacity

# umount /dev/my_vg/my_lv
# e2fsck -f /dev/my_vg/my_lv
# resize2fs -f /dev/my_vg/my_lv 10G
# lvreduce -L 10G /dev/my_vg/my_lv

Creating an LVM Snapshot

# lvcreate -s -n mylv_back -L 200M /dev/my_vg/my_lv
# lvs

Restoring from a Snapshot

# rm -fr *               # simulate data loss
# mkdir /back
# mount /dev/my_vg/mylv_back /back/
# cp -a /back/* ./