LVM Cheat Sheet

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The three-step creation flow

# 1. Tag disks as Physical Volumes
pvcreate /dev/sdb /dev/sdc

# 2. Pool them into a Volume Group
vgcreate vg_name /dev/sdb /dev/sdc

# 3. Carve out a Logical Volume
lvcreate -L 100G -n lv_name vg_name

# 4. Format
mkfs.ext4 /dev/vg_name/lv_name

# 5. Mount
mount /dev/vg_name/lv_name /mnt/point

Physical Volumes (PV)

Command	What it does
`pvcreate /dev/sdX`	Create a PV from a disk
`pvs`	Quick list of all PVs
`pvdisplay`	Full details for all PVs
`pvdisplay /dev/sdX`	Details for one PV
`pvscan`	Re-scan and find all PVs
`pvremove /dev/sdX`	Remove LVM from a disk
`pvmove /dev/sdX`	Move all data off this PV to others in VG
`pvmove /dev/sdX /dev/sdY`	Move data from sdX specifically to sdY

Volume Groups (VG)

Command	What it does
`vgcreate vg_name /dev/sdX /dev/sdY`	Create VG from one or more PVs
`vgs`	Quick list of all VGs
`vgdisplay`	Full details for all VGs
`vgdisplay vg_name`	Details for one VG
`vgscan`	Re-scan for VGs
`vgextend vg_name /dev/sdZ`	Add a new PV to an existing VG
`vgreduce vg_name /dev/sdX`	Remove a PV from a VG (PV must be empty)
`vgremove vg_name`	Delete a VG (destroys all LVs in it)
`vgrename old_name new_name`	Rename a VG
`vgchange -ay vg_name`	Activate a VG (makes LVs accessible)
`vgchange -an vg_name`	Deactivate a VG
`vgexport vg_name`	Export VG (for moving disks to another machine)
`vgimport vg_name`	Import a VG from another machine

Logical Volumes (LV)

Command	What it does
`lvcreate -L 100G -n lv_name vg_name`	Create 100 GB LV
`lvcreate -l 100%FREE -n lv_name vg_name`	Create LV using all free space
`lvcreate -l 50%VG -n lv_name vg_name`	Create LV using 50% of VG
`lvs`	Quick list of all LVs
`lvdisplay`	Full details for all LVs
`lvdisplay /dev/vg_name/lv_name`	Details for one LV
`lvscan`	Re-scan for LVs
`lvremove /dev/vg_name/lv_name`	Delete an LV (destroys data)
`lvrename vg_name old_lv new_lv`	Rename an LV

Resizing

Command	What it does
`lvextend -L +50G /dev/vg/lv`	Grow LV by 50 GB
`lvextend -L 200G /dev/vg/lv`	Grow LV to exactly 200 GB
`lvextend -l +100%FREE /dev/vg/lv`	Grow LV using all free space
`lvextend -L +50G -r /dev/vg/lv`	Grow LV + resize ext4/xfs automatically
`resize2fs /dev/vg/lv`	Resize ext4 filesystem to match LV
`xfs_growfs /mountpoint`	Grow xfs filesystem (use mountpoint, not device)
`lvreduce -L 100G /dev/vg/lv`	Shrink LV to 100 GB (unmount + resize fs first!)
`lvresize -L 100G /dev/vg/lv`	Resize LV to exactly 100 GB (grow or shrink)

Snapshots

Command	What it does
`lvcreate -L 10G -s -n snap /dev/vg/lv`	Create 10 GB snapshot of lv
`mount -o ro /dev/vg/snap /mnt/snap`	Mount snapshot read-only
`lvconvert --merge /dev/vg/snap`	Restore origin from snapshot
`lvremove /dev/vg/snap`	Delete snapshot

Status and inspection

pvs && vgs && lvs          # Quick overview of everything
lsblk                      # Block device tree (shows LVM structure)
lvmdiskscan                # Show all disks LVM can see
dmsetup ls                 # List device mapper devices
df -h                      # Filesystem usage (after mounting)

Device paths

An LV named lv_home in vg_tank appears at:

/dev/vg_tank/lv_home          ← symlink (easy to use)
/dev/mapper/vg_tank-lv_home   ← actual device node

Both work identically.

fstab entry

# Device                        Mountpoint  FS     Options    Dump Pass
/dev/vg_tank/lv_home            /home       ext4   defaults   0    2
UUID=abc123...                  /data       xfs    defaults   0    2

Using UUID in fstab is more reliable than device paths — device names like /dev/sdb can change between boots, but UUIDs don’t. Get UUIDs with blkid.

Common error messages

Error	Cause	Fix
`Couldn't find device with uuid`	LVM can’t find a PV	Run `pvscan`, check if disk is connected
`Volume group not found`	VG not activated	Run `vgchange -ay vg_name`
`Insufficient free space`	Not enough space in VG	Check `vgs`, add a disk with `vgextend`
`Snapshot has been invalidated`	Snapshot filled up	Allocate more space next time with `-L`
`resize2fs: New size smaller than minimum`	Tried to shrink too small	Check how much data is actually used with `df`
`Can't remove open logical volume`	LV is still mounted	`umount` first

Quick mental model

Disks      →    PVs       →    VG         →    LVs        →    Filesystems
/dev/sdb        tag it         pool them        carve them       use them
/dev/sdc        pvcreate       vgcreate         lvcreate         mkfs + mount

One sentence: PVs feed into a VG pool; LVs are scooped out of that pool.