Chapter 6. Modifying the size of a logical volume
After you have created a logical volume, you can modify the size of the volume.
6.1. Extending a logical volume and file system
You can extend a logical volume (LV) using the
lvextend command. You can specify by how much you want to extend the LV, or how large you want the LV to be after you extend it. Use the
-r option of the
lvextend command to grow the underlying file system along with the LV.
You can also extend logical volumes using the
lvresize command, but this command does not guarantee against accidental shrinkage.
You have an existing logical volume (LV) with a file system on it. Determine the file system type and size using the
df -Thcommand. For more information about creating a logical volume and a file system, see Creating LVM logical volume.
You have sufficient space in the volume group to grow your LV and file system. Use the
vgs -o name,vgfreecommand to determine the available space. For more information about creating volume groups, see Creating LVM volume group.
Optional: If the volume group has insufficient space to grow your LV, add a new physical volume to the volume group:
# vgextend myvg /dev/vdb3 Physical volume "/dev/vdb3" successfully created. Volume group "myvg" successfully extended.
Extend the LV and the file system:NoteNote
-Loption to extend the LV to a new size and the
-loption to specify the number of extents depending on the size of the logical volume that you want to increase.
# lvextend -r -L 3G /dev/myvg/mylv fsck from util-linux 2.32.1 /dev/mapper/myvg-mylv: clean, 11/131072 files, 26156/524288 blocks Size of logical volume myvg/mylv changed from 2.00 GiB (512 extents) to 3.00 GiB (768 extents). Logical volume myvg/mylv successfully resized. resize2fs 1.45.6 (20-Mar-2020) Resizing the filesystem on /dev/mapper/myvg-mylv to 786432 (4k) blocks. The filesystem on /dev/mapper/myvg-mylv is now 786432 (4k) blocks long.
You can also extend the mylv logical volume to fill all of the unallocated space in the myvg volume group:
# lvextend -l +100%FREE /dev/myvg/mylv Size of logical volume myvg/mylv changed from 10.00 GiB (2560 extents) to 6.35 TiB (1665465 extents). Logical volume myvg/mylv successfully resized.
Verify that the file system and the LV has grown:
# df -Th Filesystem Type Size Used Avail Use% Mounted on devtmpfs devtmpfs 1.9G 0 1.9G 0% /dev tmpfs tmpfs 1.9G 0 1.9G 0% /dev/shm tmpfs tmpfs 1.9G 8.6M 1.9G 1% /run tmpfs tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup /dev/mapper/rhel-root xfs 45G 3.7G 42G 9% / /dev/vda1 xfs 1014M 369M 646M 37% /boot tmpfs tmpfs 374M 0 374M 0% /run/user/0 /dev/mapper/myvg-mylv xfs 2.0G 47M 2.0G 3% /mnt/mnt1
6.2. Reducing a logical volume and file system
You can reduce a logical volume and its file system by using the
lvreduce command and the
If the logical volume you are reducing contains a file system, to prevent data loss you must ensure that the file system is not using the space in the logical volume that is being reduced. For this reason, use the
--resizefs option of the
lvreduce command when the logical volume contains a file system.
When you use
lvreduce attempts to reduce the file system before shrinking the logical volume. If shrinking the file system fails because it is full or does not support shrinking, then the
lvreduce command fails and does not attempt to reduce the logical volume.
In most cases, the
lvreduce command warns about possible data loss and asks for confirmation. However, you should not rely on these confirmation prompts to prevent data loss because in some cases you will not see these prompts, such as when the logical volume is inactive or the
--resizefs option is not used.
Note that using the
--test option of the
lvreduce command does not indicate if the operation is safe because this option does not check the file system or test the file system resize.
File system of the logical volume supports shrinking. Determine the file system type and size using the
For example, the GFS2 and XFS filesystems do not support shrinking.
- Underlying file system is not using the space in the LV that is being reduced.
Shrink the mylv logical volume and its filesystem in the myvg volume group using one of the following options:
Reduce the LV and its file system to a desired value:
# lvreduce --resizefs -L 500M myvg/mylv File system ext4 found on myvg/mylv. File system size (2.00 GiB) is larger than the requested size (500.00 MiB). File system reduce is required using resize2fs. ... Logical volume myvg/mylv successfully resized.
Reduce 64 megabytes from the logical volume and filesystem:
# lvreduce --resizefs -L -64M myvg/mylv File system ext4 found on myvg/mylv. File system size (500.00 MiB) is larger than the requested size (436.00 MiB). File system reduce is required using resize2fs. ... Logical volume myvg/mylv successfully resized
6.3. Extending a striped logical volume
You can extend a striped logical volume (LV) by using the
lvextend command with the required size.
- You have enough free space on the underlying physical volumes (PVs) that make up the volume group (VG) to support the stripe.
Optional: Display your volume group:
# vgs VG #PV #LV #SN Attr VSize VFree myvg 2 1 0 wz--n- 271.31G 271.31G
Optional: Create a stripe using the entire amount of space in the volume group:
# lvcreate -n stripe1 -L 271.31G -i 2 myvg Using default stripesize 64.00 KB Rounding up size to full physical extent 271.31 GiB
Optional: Extend the myvg volume group by adding new physical volumes:
# vgextend myvg /dev/sdc1 Volume group "myvg" successfully extended
Repeat this step to add sufficient physical volumes depending on your stripe type and the amount of space used. For example, for a two-way stripe that uses up the entire volume group, you need to add at least two physical volumes.
Extend the striped logical volume stripe1 that is a part of the myvg VG:
# lvextend myvg/stripe1 -L 542G Using stripesize of last segment 64.00 KB Extending logical volume stripe1 to 542.00 GB Logical volume stripe1 successfully resized
You can also extend the stripe1 logical volume to fill all of the unallocated space in the myvg volume group:
# lvextend -l+100%FREE myvg/stripe1 Size of logical volume myvg/stripe1 changed from 1020.00 MiB (255 extents) to <2.00 GiB (511 extents). Logical volume myvg/stripe1 successfully resized.
Verify the new size of the extended striped LV:
# lvs LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert stripe1 myvg wi-ao---- 542.00 GB