• Mohammed Niyas

How to extend and Shrink LVM

Post: How to create LVM


In the previous article, I have explained well about how to create a LVM. In this article, i will show how to extend LVM.


1. To see current LVM in a linux, run the following

[root@localhost ~]# lvscan
  ACTIVE            '/dev/new_group/new_lvm' [2.00 GiB] inherit
  ACTIVE            '/dev/rhel/swap' [<3.94 GiB] inherit
  ACTIVE            '/dev/rhel/root' [<35.06 GiB] inherit

2. Check the current physical volumes labeled.

[root@localhost ~]# pvscan
  PV /dev/nvme0n4     VG new_group       lvm2 [<3.00 GiB / 1020.00 MiB free]
  PV /dev/nvme0n5     VG new_group       lvm2 [<3.00 GiB / <3.00 GiB free]
  PV /dev/nvme0n6     VG new_group       lvm2 [<3.00 GiB / <3.00 GiB free]
  PV /dev/nvme0n1p2   VG rhel            lvm2 [<39.00 GiB / 0    free] 	

3. Display the block devices details using lsblk

[root@localhost ~]# lsblk
NAME                MAJ:MIN RM    SIZE RO TYPE MOUNTPOINT
sr0                  11:0    1   1024M  0 rom  
nvme0n1             259:0    0     40G  0 disk 
├─nvme0n1p1         259:1    0      1G  0 part /boot
├─nvme0n1p2         259:2    0     39G  0 part 
│ ├─rhel-root       253:0    0   35.1G  0 lvm  /
│ └─rhel-swap       253:1    0      4G  0 lvm  [SWAP]
└─nvme0n1p3         259:3    0 1023.5K  0 part 
nvme0n2             259:4    0      5G  0 disk 
└─nvme0n2p1         259:5    0   1023M  0 part 
nvme0n3             259:6    0      5G  0 disk 
└─nvme0n3p1         259:7    0      5G  0 part /mymount1
nvme0n4             259:8    0      3G  0 disk 
└─new_group-new_lvm 253:2    0      2G  0 lvm  /lvdrive
nvme0n5             259:9    0      3G  0 disk 
nvme0n6             259:10   0      3G  0 disk 
nvme0n7             259:11   0      3G  0 disk 

4. Create a physical volume

[root@localhost ~]# pvcreate /dev/nvme0n7
  Physical volume "/dev/nvme0n7" successfully created.

5. Display the volume groups.

[root@localhost ~]# vgs
  VG        #PV #LV #SN Attr   VSize   VFree 
  new_group   3   1   0 wz--n-  <8.99g <6.99g
  rhel        1   2   0 wz--n- <39.00g     0 

6. The new physical volume is added to volume "new_group"

[root@localhost ~]# vgextend new_group /dev/nvme0n7
  Volume group "new_group" successfully extended

7. Run vgs again to see the capacity difference after adding new physical volume

[root@localhost ~]# vgs
  VG        #PV #LV #SN Attr   VSize   VFree
  new_group   4   1   0 wz--n-  11.98g 9.98g
  rhel        1   2   0 wz--n- <39.00g    0 

8. Run pvscan to display the physical volumes in each volume group

[root@localhost ~]# pvscan
  PV /dev/nvme0n4     VG new_group       lvm2 [<3.00 GiB / 1020.00 MiB free]
  PV /dev/nvme0n5     VG new_group       lvm2 [<3.00 GiB / <3.00 GiB free]
  PV /dev/nvme0n6     VG new_group       lvm2 [<3.00 GiB / <3.00 GiB free]
  PV /dev/nvme0n7     VG new_group       lvm2 [<3.00 GiB / <3.00 GiB free]
  PV /dev/nvme0n1p2   VG rhel            lvm2 [<39.00 GiB / 0    free]
  Total: 5 [50.98 GiB] / in use: 5 [50.98 GiB] / in no VG: 0 [0   ]

9. Run lvextend to expand the volume group.

In the first command, "lvextend -L3G /dev/new_group/new_lvm"increase total volume to 3GB.

In the second command, "lvextend -L+1G /dev/new_group/new_lvm" increase additional volume 1G to the existing LVM size.

[root@localhost ~]# lvextend -L3G /dev/new_group/new_lvm
  Size of logical volume new_group/new_lvm changed from 2.00 GiB (512 extents) to 3.00 GiB (768 extents).
  Logical volume new_group/new_lvm successfully resized.
[root@localhost ~]# lvextend -L+1G /dev/new_group/new_lvm
  Size of logical volume new_group/new_lvm changed from 3.00 GiB (768 extents) to 4.00 GiB (1024 extents).
  Logical volume new_group/new_lvm successfully resized.

10. Finally run lvdisplay for detailed view of LVM

[root@localhost ~]# lvdisplay /dev/new_group/new_lvm 
  --- Logical volume ---
  LV Path                /dev/new_group/new_lvm
  LV Name                new_lvm
  VG Name                new_group
  LV UUID                IdF48L-McZI-inff-3RW0-mNak-ADYO-tVcMxq
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2021-06-12 03:57:35 -0400
  LV Status              available
  # open                 1
  LV Size                4.00 GiB
  Current LE             1024
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:2

How to Shrink LVM

  1. lvreduce command is used to shrink the size of LVM

In this command, i reduce the entire LVM size to 1 GB.

[root@localhost ~]# lvreduce -L 1GB /dev/new_group/new_lvm
  WARNING: Reducing active and open logical volume to 1.00 GiB.
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce new_group/new_lvm? [y/n]: y
  Size of logical volume new_group/new_lvm changed from 4.00 GiB (1024 extents) to 1.00 GiB (256 extents).
  Logical volume new_group/new_lvm successfully resized.

2. But if you only what to reduce 1 GB from total, then run '-' sign before the size value.

[root@localhost ~]# lvreduce -L -1GB /dev/new_group/new_lvm
  WARNING: Reducing active and open logical volume to 2.00 GiB.
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce new_group/new_lvm? [y/n]: y
  Size of logical volume new_group/new_lvm changed from 3.00 GiB (768 extents) to 2.00 GiB (512 extents).
  Logical volume new_group/new_lvm successfully resized.

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