Logical Volume Manager (LVM) is a storage management system/technology used on Linux to manage hard drives and other storage devices.
In this guide, we will briefly look at how LVM works and the basic commands needed to get you up and running quickly.
Package Installation
For RPM based distributions:
For DEB based distributions
LVM Storage Terms
Physical Volumes:
- Prefix
pv
- Description: Physical disks. /dev/sda,/dev/hda etc
Volume Group:
- Prefix
vg
- Description: Combination of physical volumes into storage pools
Logical Volumes:
- Prefix
lv
- Description: Volume group broken down into slices, volume groups, partitions
Extents:
- Description: Each volume within a volume group is segmented into small, fixed-size chunks called extents. The size of the extents is
determined by the volume group (all volumes within the group conform to the same extent size).
The extents on a physical volume are called physical extents, while the extents of a logical volume are called logical extents. A logical
volume is simply a mapping that LVM maintains between logical and physical extents. Because of this relationship, the extent size represents
the smallest amount of space that can be allocated by LVM.
Scan System
Scan the system for block devices
You should see this depending on your drives
/dev/sda2 [ <13.00 GiB]
/dev/sdb [ 13.00 GiB]
/dev/sdc [ 13.00 GiB]
/dev/sdd [ 13.00 GiB]
3 disks
1 partition
0 LVM physical volume whole disks
0 LVM physical volumes
Create Partitions
List Block Devices
You should see this
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 13G 0 disk
├─sda1 8:1 0 1M 0 part
└─sda2 8:2 0 13G 0 part /
sdb 8:16 0 13G 0 disk
sdc 8:32 0 13G 0 disk
sdd 8:48 0 13G 0 disk
sr0 11:0 1 1024M 0 rom
Run fdisk on /dev/sdb, /dev/sdc, /dev/sdd and accept defaults. You should see this when completed
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 13G 0 disk
├─sda1 8:1 0 1M 0 part
└─sda2 8:2 0 13G 0 part /
sdb 8:16 0 13G 0 disk
└─sdb1 8:17 0 13G 0 part
sdc 8:32 0 13G 0 disk
└─sdc1 8:33 0 13G 0 part
sdd 8:48 0 13G 0 disk
└─sdd1 8:49 0 13G 0 part
sr0 11:0 1 1024M 0 rom
Create Physical Volumes
Create physical volumes
sudo pvcreate /dev/sdb1
sudo pvcreate /dev/sdc1
sudo pvcreate /dev/sdd1
You should have these respectively
Physical volume "/dev/sdb1" successfully created.
Physical volume "/dev/sdc1" successfully created.
Physical volume "/dev/sdd1" successfully created.
List Physical Volumes
You should see this
"/dev/sdb1" is a new physical volume of "<13.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdb1
VG Name
PV Size <13.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID nBxpTQ-ZCDY-ScZy-oZj2-0WC8-QbbF-jJ4965
"/dev/sdd1" is a new physical volume of "<13.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdd1
VG Name
PV Size <13.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID KV0CFJ-EwcP-yjKK-3ejR-y69y-6Icc-rY53th
"/dev/sdc1" is a new physical volume of "<13.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdc1
VG Name
PV Size <13.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID e4WEPR-Rtxk-yECB-Z4je-cDt6-J3w9-u0JQ9I
Create Volume Group
With our physical volumes in place, we can now create our volume group
sudo vgcreate devpoc_vg /dev/sdb1
OR
sudo vgcreate prodpoc_vg /dev/sdb1 /dev/sdc1 /dev/sdd1
Not Both
using prodpoc_vg in this case, we have
Volume group "prodpoc_vg" successfully created
List volume group
You should seee this
--- Volume group ---
VG Name prodpoc_vg
System ID
Format lvm2
Metadata Areas 3
Metadata Sequence No 1
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 3
Act PV 3
VG Size <38.99 GiB
PE Size 4.00 MiB
Total PE 9981
Alloc PE / Size 0 / 0
Free PE / Size 9981 / <38.99 GiB
VG UUID CaLrye-GWnD-Kmo1-2MZb-rdEV-hJtP-fso1LD
If we go the route of sudo vgcreate devpoc_vg /dev/sdb1 we can do this
sudo vgcreate devpoc_vg /dev/sdb1
sudo vgextend devpoc_vg /dev/sdc1
in this case, we create and extend
Create Logical Volumes
With our volume group in place, we can now create our logical volumes. Lets create three logical volumes
with 200MB,400MB and 2GB
sudo lvcreate -L 200 -n store1 prodpoc_vg
sudo lvcreate -L 400 -n store2 prodpoc_vg
sudo lvcreate -L 2000 -n store3 prodpoc_vg
You should see this respectively
Logical volume "store1" created.
Logical volume "store2" created.
Logical volume "store3" created.
To list your logical volumes
we should see this
--- Logical volume ---
LV Path /dev/prodpoc_vg/store1
LV Name store1
VG Name prodpoc_vg
LV UUID Nqf88X-FLqL-XVv6-l4BN-tst5-T2cz-1hEVrc
LV Write Access read/write
LV Creation host, time test-svr, 2021-04-21 07:56:20 +0000
LV Status available
# open 0
LV Size 200.00 MiB
Current LE 50
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:0
--- Logical volume ---
LV Path /dev/prodpoc_vg/store2
LV Name store2
VG Name prodpoc_vg
LV UUID gfGOI5-FV7t-84gb-Nl3P-7uWo-hyCp-1E3J4J
LV Write Access read/write
LV Creation host, time test-svr, 2021-04-21 07:56:29 +0000
LV Status available
# open 0
LV Size 400.00 MiB
Current LE 100
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:1
--- Logical volume ---
LV Path /dev/prodpoc_vg/store3
LV Name store3
VG Name prodpoc_vg
LV UUID 4vXGSa-egWg-zwhF-fCSc-vtZE-HOTb-ywEiTI
LV Write Access read/write
LV Creation host, time test-svr, 2021-04-21 07:56:36 +0000
LV Status available
# open 0
LV Size 1.95 GiB
Current LE 500
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:2
Create Filesystem
With our logical volumes in place, we can now create our filesystem
sudo mkfs.ext4 /dev/prodpoc_vg/store1
sudo mkfs.ext4 /dev/prodpoc_vg/store2
sudo mkfs.ext4 /dev/prodpoc_vg/store3
Create folders to mount the filesystem
Mount filesystem /etc/fstab
/dev/prodpoc_vg/store1 /home/ubuntu/st1 ext4 defaults 0 0
/dev/prodpoc_vg/store2 /home/ubuntu/st2 ext4 defaults 0 0
/dev/prodpoc_vg/store3 /home/ubuntu/st3 ext4 defaults 0 0
sudo mount -a. Type df -a and you should see this
Filesystem Size Used Avail Use% Mounted on
udev 966M 0 966M 0% /dev
tmpfs 200M 732K 199M 1% /run
/dev/sda2 13G 4.0G 8.2G 33% /
tmpfs 997M 0 997M 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 997M 0 997M 0% /sys/fs/cgroup
tmpfs 200M 0 200M 0% /run/user/1000
/dev/mapper/prodpoc_vg-store1 190M 1.6M 175M 1% /home/ubuntu/st1
/dev/mapper/prodpoc_vg-store2 380M 2.3M 354M 1% /home/ubuntu/st2
/dev/mapper/prodpoc_vg-store3 1.9G 5.9M 1.8G 1% /home/ubuntu/st3
Extend Logical Volume
With our filesystem in place, lets extend one of our logical volumes. We will add 3GB to /dev/prodpoc_vg/store2
sudo lvextend -L +3000 /dev/prodpoc_vg/store2
you should see something like this
Size of logical volume prodpoc_vg/store2 changed from 400.00 MiB (100 extents) to 3.32 GiB (850 extents).
Logical volume prodpoc_vg/store2 successfully resized.
Now we resize it
sudo resize2fs /dev/prodpoc_vg/store2
you should see something like this
resize2fs 1.44.1 (24-Mar-2018)
Filesystem at /dev/prodpoc_vg/store2 is mounted on /home/ubuntu/st2; on-line resizing required
old_desc_blocks = 4, new_desc_blocks = 27
The filesystem on /dev/prodpoc_vg/store2 is now 3481600 (1k) blocks long.
Testing out with df -h we can see our changes
Filesystem Size Used Avail Use% Mounted on
udev 966M 0 966M 0% /dev
tmpfs 200M 732K 199M 1% /run
/dev/sda2 13G 4.0G 8.2G 33% /
tmpfs 997M 0 997M 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 997M 0 997M 0% /sys/fs/cgroup
tmpfs 200M 0 200M 0% /run/user/1000
/dev/mapper/prodpoc_vg-store1 190M 1.6M 175M 1% /home/ubuntu/st1
/dev/mapper/prodpoc_vg-store2 3.3G 3.0M 3.1G 1% /home/ubuntu/st2
/dev/mapper/prodpoc_vg-store3 1.9G 5.9M 1.8G 1% /home/ubuntu/st3
Remove Logical Volume
We can also remove the logical volumes if we no longer need them. In this case /dev/prodpoc_vg/store1
sudo lvremove /dev/prodpoc_vg/store1
answer yes
Do you really want to remove and DISCARD active logical volume prodpoc_vg/store1? [y/n]: y
Logical volume "store1" successfully removed
Remember to unmount first
Command Summary Reference*
List of PV Commands
- pvchange: — Change attributes of a Physical Volume.
- pvck: — Check Physical Volume metadata.
- pvcreate: — Initialize a disk or partition for use by LVM.
- pvdisplay: — Display attributes of a Physical Volume.
- pvmove: — Move Physical Extents.
- pvremove: — Remove a Physical Volume.
- pvresize: — Resize a disk or partition in use by LVM2.
- pvs: — Report information about Physical Volumes.
- pvscan: — Scan all disks for Physical Volumes.
List of VG commands
- vgcfgbackup: — Backup Volume Group descriptor area.
- vgcfgrestore: — Restore Volume Group descriptor area.
- vgchange: — Change attributes of a Volume Group.
- vgck: — Check Volume Group metadata.
- vgconvert: — Convert Volume Group metadata format.
- vgcreate: — Create a Volume Group.
- vgdisplay: — Display attributes of Volume Groups.
- vgexport: — Make volume Groups unknown to the system.
- vgextend: — Add Physical Volumes to a Volume Group.
- vgimport: — Make exported Volume Groups known to the system.
- vgimportclone: — Import and rename duplicated Volume Group (e.g. a hardware snapshot).
- vgmerge: — Merge two Volume Groups.
- vgmknodes: — Recreate Volume Group directory and Logical Volume special files
- vgreduce: — Reduce a Volume Group by removing one or more Physical Volumes.
- vgremove: — Remove a Volume Group.
- vgrename: — Rename a Volume Group.
- vgs: — Report information about Volume Groups.
- vgscan: — Scan all disks for Volume Groups and rebuild caches.
- vgsplit: — Split a Volume Group into two, moving any logical volumes from one Volume Group to another by moving entire Physical Volumes.
List of LV commands
- lvchange: — Change attributes of a Logical Volume.
- lvconvert: — Convert a Logical Volume from linear to mirror or snapshot.
- lvcreate: — Create a Logical Volume in an existing Volume Group.
- lvdisplay: — Display the attributes of a Logical Volume.
- lvextend: — Extend the size of a Logical Volume.
- lvreduce: — Reduce the size of a Logical Volume.
- lvremove: — Remove a Logical Volume.
- lvrename: — Rename a Logical Volume.
- lvresize: — Resize a Logical Volume.
- lvs: — Report information about Logical Volumes.
- lvscan: — Scan (all disks) for Logical Volumes.
Reference Links