What are the three LVM layers?

Physical Volumes (PVs) are raw disks or partitions initialised with pvcreate. Volume Groups (VGs) pool one or more PVs into a single storage space with vgcreate. Logical Volumes (LVs) are carved out of a VG with lvcreate and act like partitions you format and mount. The pv*, vg* and lv* command families map to these layers.

How do I grow a logical volume?

Extend the LV with lvextend -L +10G /dev/vg/lv (or -l +100%FREE to use all free extents), then grow the filesystem with resize2fs for ext4 or xfs_growfs for XFS. lvextend -r does both in one step by calling the filesystem resize automatically.

What is an LVM snapshot?

A snapshot is a point-in-time copy created with lvcreate -s -L 1G -n snap /dev/vg/lv. It uses copy-on-write: only blocks that change after the snapshot consume space. Snapshots are ideal for consistent backups, but they fill up and become invalid if the changed data exceeds the snapshot size.

What is the difference between -L and -l?

-L specifies size in human units like -L 20G or -L 500M. -l specifies size in extents or a percentage, such as -l 100%FREE to consume all free space in the VG or -l 50%VG for half the group. Use -L for fixed sizes and -l when you want to fill available space.

How do I remove LVM cleanly?

Remove in reverse order: unmount the filesystem, lvremove /dev/vg/lv, then vgremove vg once all its LVs are gone, then pvremove /dev/sdX to wipe the LVM label from the disk. vgreduce removes a PV from a group, and pvmove first migrates its data to other PVs.

Linux LVM Commands Reference

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What LVM does

The Linux Logical Volume Manager adds a flexible layer between physical disks and filesystems. Raw disks become Physical Volumes, PVs are pooled into a Volume Group, and Logical Volumes are carved from that pool — resizable, movable and snapshottable without repartitioning. The command set mirrors these layers: pv* for physical volumes, vg* for groups, lv* for logical volumes. This reference lists the commands you actually use, with their key flags.

How it works

Provisioning flows top-down through the three layers, then you format and mount the resulting LV like any block device:

pvcreate /dev/sdb /dev/sdc          # initialise disks as PVs
vgcreate datavg /dev/sdb /dev/sdc   # pool them into a VG
lvcreate -L 50G -n web datavg       # carve a 50G LV named "web"
mkfs.ext4 /dev/datavg/web           # format it
mount /dev/datavg/web /srv/web      # mount it

Growing later is two steps: lvextend -L +20G /dev/datavg/web then a filesystem resize, or lvextend -r to do both. Snapshots (lvcreate -s) give you a copy-on-write point-in-time view for backups.

Tips and notes

lvextend -r resizes the filesystem in one step — no separate resize2fs.
-l 100%FREE consumes all remaining extents; -L takes a fixed human size.
Use pvmove before vgreduce to drain a disk you want to remove from a group.
Thin pools (lvcreate --type thin-pool) allow over-provisioning — monitor pool usage closely to avoid running out of backing space.