In the previous article, we have covered what is LVM and how to create Volume group and Logical volumes in Linux. This article will teach you how to resize LVM partitions i.e. extend a Volume Group and Logical Volume's size and reduce/shrink Logical Volume's size in Linux.
When you want to increase the size of your logical volume, you should check if there are any unallocated spaces in the free pool (i.e. Volume Group).
If there is no space left in the free pool, then you have to go with any of the below steps to increase the space.
- Check if any volume group has space that can be utilized. In this case, add the space back to the volume group and increase the new volume size.
- Add a disk, initialize it as physical volume and add it to the volume group using which you can extend the logical volume size.
My Existing Setup
For demonstration purpose, I have created an Ubuntu 20.04 test machine using Vagrant and Virtualbox. I have two disks that are initialized as a physical volume.
$ sudo pvscan
PV /dev/sdc VG ostechnix_files lvm2 [<5.00 GiB / 96.00 MiB free] PV /dev/sdd lvm2 [10.00 GiB] Total: 2 [<15.00 GiB] / in use: 1 [<5.00 GiB] / in no VG: 1 [10.00 GiB]
Among these two disks, only the
/dev/sdc partition is added to the volume group
ostechnix_files and created logical volume from that.
$ sudo lvdisplay
--- Logical volume --- LV Path /dev/ostechnix_files/guides LV Name guides VG Name ostechnix_files LV UUID dc1gzT-cyLX-axdh-0EpD-GHBB-un8s-B5JAAc LV Write Access read/write LV Creation host, time ubuntu, 2022-12-04 15:33:59 +0000 LV Status available # open 1 LV Size 4.90 GiB Current LE 1255 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:0
Extending Volume Group and Logical Volume
I have no space left on the free pool (VG) to increase the size of the logical volume, so I have to add space to the volume group first to extend logical volumes.
$ sudo vgdisplay ostechnix_files | grep -i Free Free PE / Size 24 / 96.00 MiB
I already have a disk of 10GB initialized as a physical volume. You can find the steps to create PV in the LVM introduction article.
$ sudo pvdisplay /dev/sdd "/dev/sdd" is a new physical volume of "10.00 GiB" --- NEW Physical volume --- PV Name /dev/sdd VG Name PV Size 10.00 GiB Allocatable NO PE Size 0 Total PE 0 Free PE 0 Allocated PE 0 PV UUID obm8bR-pIUs-VmWc-BN61-xAXQ-WZmm-WtCsOT
Extend Volume Group
We can use
vgextend command to add the new initialized space to the volume group (i.e.
##Syntax $ vgextend <volume-group-name> <physical-volume>
Now we run the vgextend command to add the space to the volume group
$ sudo vgextend ostechnix_files /dev/sdd Volume group "ostechnix_files" successfully extended
You can run any of the following commands to get the logical volume path for which you wish to extend the size.
$ sudo lvdisplay $ sudo lvdisplay | grep -i path LV Path /dev/ostechnix_files/guides
Extend Logical Volume
We can use the
lvextend command to increase the logical volume size.
I am extending the size from 4.9 GB to 6.9 GB by adding 2GB from the free pool (VG).
$ sudo lvextend -L +2G /dev/ostechnix_files/guides
+2G indicates that we are increasing the size by 2 GB.
Size of logical volume ostechnix_files/guides changed from 4.90 GiB (1255 extents) to 6.90 GiB (1767 extents). Logical volume ostechnix_files/guides successfully resized.
Now you can check the LV Size by running any of the following commands.
$ sudo lvdisplay $ sudo lvdisplay | grep -i size LV Size 6.90 GiB
Please note that resizing has only increased the volume size but not the file system size. We can verify it using
$ df -h /dev/ostechnix_files/guides
Filesystem Size Used Avail Use% Mounted on /dev/mapper/ostechnix_files-guides 4.8G 20M 4.5G 1% /mnt
We can increase the filesystem size using the
resize2fs command. Resizing can be done without unmounting the filesystem.
$ sudo resize2fs /dev/mapper/ostechnix_files-guides
resize2fs 1.45.5 (07-Jan-2020) Filesystem at /dev/mapper/ostechnix_files-guides is mounted on /mnt; on-line resizing required old_desc_blocks = 1, new_desc_blocks = 1 The filesystem on /dev/mapper/ostechnix_files-guides is now 1809408 (4k) blocks long.
Now let us verify if the partition size is really extended with
$ df -h /dev/mapper/ostechnix_files-guides
Filesystem Size Used Avail Use% Mounted on /dev/mapper/ostechnix_files-guides 6.8G 23M 6.4G 1% /mnt
As you can see in the above output, the Volume Group is extended to 6.8 GB.
Reduce or Shrink Logical Volume
As stated already in the previous section, sometimes you may need to borrow some space from an existing logical volume and add it to some other volumes. For this, you have to first shrink the logical volume and add the space back to the volume group. Then you will extend the size of the logical volume from the free pool(VG).
The first step is to unmount the file system. You cannot shrink the volume or file system when the file system is mounted.
$ umount <file-system-path>
To make sure there are no issues with the volume, run the
$ sudo fsck /dev/mapper/ostechnix_files-guides
fsck from util-linux 2.34 e2fsck 1.45.5 (07-Jan-2020) /dev/mapper/ostechnix_files-guides: clean, 11/449792 files, 50275/1809408 blocks
Now the file system size can be reduced. I am going to resize the filesystem to 4 GB.
To do so, we use
$ sudo resize2fs /dev/mapper/ostechnix_files-guides 4G
resize2fs 1.45.5 (07-Jan-2020) Resizing the filesystem on /dev/mapper/ostechnix_files-guides to 1048576 (4k) blocks. The filesystem on /dev/mapper/ostechnix_files-guides is now 1048576 (4k) blocks long.
Now run the
lvreduce command to shrink the logical volume and add it back to the volume group. Here I am reclaiming 2 GB from the LV.
$ sudo lvreduce -L -2G /dev/ostechnix_files/guides
-2G indicates that we are decreasing the size by 2 GB.
WARNING: Reducing active logical volume to 4.90 GiB. THIS MAY DESTROY YOUR DATA (filesystem etc.) Do you really want to reduce ostechnix_files/guides? [y/n]: y Size of logical volume ostechnix_files/guides changed from 6.90 GiB (1767 extents) to 4.90 GiB (1255 extents). Logical volume ostechnix_files/guides successfully resized.
Now the space is added back to the volume group. We can verify it using
$ vgdisplay ostechnix_files | grep -i "/ Size"
Alloc PE / Size 1255 / 4.90 GiB Free PE / Size 2583 / <10.09 GiB
We have to remount the existing file system which we unmounted to shrink the file system. It is safe to run the
fsck command again to check for any issues.
$ sudo fsck /dev/mapper/ostechnix_files-guides $ sudo resize2fs /dev/mapper/ostechnix_files-guides
Now mount the filesystem using command:
$ mount /dev/mapper/ostechnix_files-guides /mnt/
At this stage, you should be having a fair amount of understanding on resizing LVM partitions if you followed this article along with hands-on.
As you can see, Extending Volume Group and Logical Volume's size is simple and straightforward. However, shrinking the Logical Volume's size should be done with extra caution as it may lead to corrupting your existing data.