Master Linux LVM: Step‑by‑Step Guide to Creating and Extending Logical Volumes

Logical Volumes

Using hard disks on Linux

Partition

Partitions cannot be expanded; they must be recreated, which leads to data loss.

They require contiguous space on the disk.

Formatting

Mounting

Logical volumes (virtual disks)

Unlimited expansion without affecting data.

Space can be non‑contiguous.

Limited backup capabilities.

Process of creating logical volumes

Physical Volume (PV): split a disk partition into Physical Extents (PE), each 4 MiB.

Benefit: after partitioning, the entire disk becomes a series of 4 MiB PEs.

Volume Group (VG): a collection of PEs for easier management.

Logical Volume (LV): the virtual disk you work with.

Main commands:

Physical volume management : pvscan, pvcreate, pvdisplay, pvremove

Volume group management : vgscan, vgcreate, vgdisplay, vgremove, vgextend

Logical volume management : lvscan, lvcreate, lvdisplay, lvremove, lvextend

Creating a Physical Volume

pvcreate /dev/sdb /dev/sdc

Check with pvdisplay:

If using partitions, change the partition type to 8e before creating the PV.

Creating a Volume Group

vgcreate ky33 /dev/sdb /dev/sdc

Verify with vgdisplay:

Creating a Logical Volume

lvcreate -n chen -L 15G ky33

Check with lvdisplay:

Format the logical volume (e.g., XFS):

Mounting

Mount the logical volume permanently and refresh with mount -a:

Expanding Without Data Loss

If the volume group has enough free space, extend the logical volume directly.

If not, first extend the volume group, then extend the logical volume.

Logical volume expansion command:

lvextend -L +5G <LV_NAME> -r