Linux Disk Management: The Power of LVM

In the old days, disk partitions (like /dev/sda1) were rigid. If /var filled up and /home was empty, you had to reformat. LVM (Logical Volume Manager) adds a layer of abstraction.

The Hierarchy

1. Physical Volume (PV): The actual disk or partition (/dev/sdb).
2. Volume Group (VG): A pool of storage created by combining PVs.
3. Logical Volume (LV): The virtual partition you actually format and mount (/dev/mapper/vg-lv_root).

Scenario: Expanding Storage

You add a new 100GB hard drive (/dev/sdc) and want to add it to your root filesystem.

1. Initialize PV: pvcreate /dev/sdc
2. Extend VG: vgextend ubuntu-vg /dev/sdc (Adds disk to the pool).
3. Extend LV: lvextend -l +100%FREE /dev/ubuntu-vg/root (Give space to partition).
4. Resize FS: resize2fs /dev/ubuntu-vg/root (Tell Linux filesystem to use new space).

Done. Online. No reboot required.

Snapshots

LVM allows you to take a "frozen" snapshot of a volume. Ideal for backups: Take snapshot -> Backup snapshot -> Delete snapshot. This ensures the backup is consistent even if the live data changes during the copy process.