I'm not gonna try to convince you to use LVM. Here, I'm just gonna show you how to use this beautiful level of abstraction.
This is more a cheatsheet than a complete tutorial.
Table of Contents
Physical Volume (PV)
Description
Physical system (disks, partitions, RAID); used as raw hardware to build the architecture with a higher level of abstraction.
LVM writes a header to the hardware, indicating its manageability by LVM.
Create a PV
sudo lvmdiskscan
# Displays all disks potentially manageable by lvm
sudo pvcreate /dev/sda /dev/sdb
# ⤷ Output pvcreate :
# Physical volume "/dev/sda" successfully created
# Physical volume "/dev/sdb" successfully created
Display infos of PVs
sudo pvs
# For more details, use :
sudo pvdisplay
# ⤷ Output pvs :
# PV VG Fmt Attr PSize PFree
# /dev/sda lvm2 --- 200.00g 200.00g
# /dev/sdb lvm2 --- 100.00g 100.00g
Volume Group (VG)
Description
LVM combines Physical Volumes into a group. These groups abstract from the underlying characteristics of the physical devices and therefore function as a unified whole that combines the storage capabilities of the Physical Volumes.
Create a VG
sudo vgcreate <NAME_VG> /dev/sda /dev/sdb
# PV previously tagged
# ⤷ Output vgcreate :
# Volume group "NAME_VG" successfully created
Display infos of VGs
sudo vgs
# For more details, use :
sudo vgdisplay
# ⤷ Output vgs :
# VG #PV #LV #SN Attr VSize VFree
# NAME_VG 2 0 0 wz--n- 299.99g 299.99g
Note: now that our Physical Volumes are associated with a Volume Group, when pvs is run, the VG column now points to the Volume Group name.
Manipulations
Remove a VG
sudo umount /dev/<NAME_VG>/<ALL_LVS>
sudo vgremove <NAME_VG>
Logical Volume (LV)
Description
A Volume Group can now be divided into a number of Logical Volumes. These Logical Volumes are functionally equivalent to a partition on a physical disk, while retaining much more flexibility. These Logical Volumes are the primary components that users and applications use.
Create a LV
sudo lvcreate -L <10G> -n <NAME_LV1> <NAME_VG>
# To create a LV <NAME_LV2> that uses all the remaining space available on <NAME_VG> :
sudo lvcreate -l 100%FREE -n <NAME_LV2> <NAME_VG>
# ⤷ Output lvcreate :
# Logical volume "NAME_LV1" created.
# Logical volume "NAME_LV2" created.
Display infos of LVs
sudo lvs
# For more details, use :
sudo lvdisplay
# ⤷ Output lvs :
# LV VG Attr Lsize
# NAME_LV1 NAME_VG -wi-ao---- 10,00g
# NAME_LV1 NAME_VG -wi-ao---- 100,00g
How to access LVs
Logical Volumes are accessible via /dev/NAME_VG/NAME_LV1 or /dev/mapper/NAME_VG-NAME_LV1; for formatting or mounting, for example.
Create a snapshot
sudo lvcreate –s –L <10G> -n <NAME_SNAP> <NAME_VG>/<NAME_LV1>
Manipulations
Enlarge a LV
sudo lvresize -L <+5G> --resizefs <NAME_VG>/<NAME_LV1>
# Adds 5G to LV and also extends its filesystem
Shrink a LV
df -h # Evaluate the size we can recover
sudo umount /dev/<NAME_VG>/<NAME_LV1> # Unmount the LV
sudo fsck -t ext4 -f /dev/<NAME_VG>/<NAME_LV1> # Check the file system
sudo resize2fs -p /dev/<NAME_VG>/<NAME_LV1> <5G> # Shrink the size of the filesystem
sudo lvresize -L <5G> /dev/<NAME_VG>/<NAME_LV1> # Shrink LV size
sudo fsck -t ext4 -f /dev/<NAME_VG>/<NAME_LV1> # Control the filesystem
sudo mount /dev/<NAME_VG>/<NAME_LV1> /mnt/... # Mount the LV
Remove a LV
sudo umount /dev/<NAME_VG>/<NAME_LV1>
sudo lvremove <NAME_VG>/<NAME_LV1>
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