LVM fundamentals

The storage stack

A physical volume (PV) is a disk or partition initialised for LVM. A volume group (VG) pools PV capacity. A logical volume (LV) allocates space from the VG. Filesystems sit on top of LVs.

Inspect first

pvs
vgs
lvs -a -o +devices
lsblk -f

Create a lab volume

sudo pvcreate /dev/sdb
sudo vgcreate vg_lab /dev/sdb
sudo lvcreate -L 5G -n lv_data vg_lab
sudo mkfs.ext4 /dev/vg_lab/lv_data

Grow an ext4 LV

sudo lvextend -r -L +2G /dev/vg_lab/lv_data

Caution

Device paths are examples only. pvcreate overwrites LVM metadata on the target. Back up before resizing. XFS can grow but cannot be shrunk in place.