In this article I will show you how to expand an LVM volume or partition in Linux by first resizing logical volume, advantage of resizing the file system to take advantage of the additional space.
In my example I am going to expand logical volume /var/centos/var from 5GB to 10GB. Currently I have mounted logical volume to /mnt.
Logical Volume Manager (LVM) Overview
Before resizing process it is important you first understand some lvm basic concepts around physical volumes, volume groups, logical volumes and the file system.
- Physical Volume (PV) : PV can be create on a whole physical disk like /dev/sda or a Linux partition.
- Volume Group (VG) : VG can be created with at least one or more PV (physical volumes).
- Logical Volume (LV) : This is also called partition, it sits within a VG ( volume group ) and has a file system written to it.
- File System : File system such as ext3 or ext4 will be on the logical volume (LV)
Increase and expand the logical volume (LVM)
We can increase the lvm on fly with no downtime or mount the volume without interruption. To resize the LV, VG that it is in must have free space available.
Check free space of VG (volume group)
Run vgdisplay command as shown below and look at the “Free PE / Size” field.
# vgdisplay --- Volume group --- VG Name centos System ID Format lvm2 Metadata Areas 2 Metadata Sequence No 6 VG Access read/write VG Status resizable MAX LV 0 Cur LV 3 Open LV 2 Max PV 0 Cur PV 2 Act PV 2 VG Size 20.74 GiB PE Size 4.00 MiB Total PE 5309 Alloc PE / Size 4030 / 15.74 GiB Free PE / Size 1280 / 5.00 GiB VG UUID VvG6Sp-wIgb-LTh0-szdU-s9R1-a6K9-qHassI
Above you can see there is 5GB of free space is available in the volume group, as shown by “Free PE / Size 1279 / 5.00 GiB”.
Note :- If you do not have enough free space in the volume group, you will first need to extend the volume group (VG) to extend the LV, or Alternatively if you have multiple LVM partitions, you could shrink a different logical volume first to create space within the volume group.
Now that we have confirmed there is space free within the volume group, confirm the name of the logical volume you want to increase as well as how much space you plan on adding. The below lvdisplay command will show all logical volumes and their current size. It will also show the volume group that the logical volume is a member of, so ensure that the correct volume group has been checked for enough space with vgdisplay as previously mentioned to prevent trying to increase a logical volume that is inside some other volume group.
As shown in the example below, we are going to be working with the logical volume “var” which is in volume group “centos”, the volume group we saw in vgdisplay.
In my example I only have just the one volume group, but there may have more so you need to check first.
# lvdisplay --- Logical volume --- LV Path /dev/centos/var LV Name var VG Name centos LV UUID 7PNgg2-ZmnG-a26g-zRoT-PRVM-RDc1-oq6J4M LV Write Access read/write LV Creation host, time CentOS7, 2015-04-16 07:50:25 +1000 LV Status available # open 0 LV Size 5.00 GiB Current LE 1280 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:2
Now it’s time to expand the logical volume. In the below example we are using the -L flag to increase by a size specified (M for Megabytes, G for Gigabytes, T for Terabytes). You can alternatively remove the + to increase to the amount specified rather than by the amount specified.
# lvextend -L+5G /dev/centos/var Rounding size to boundary between physical extents: 4.90 GiB Size of logical volume centos/var changed from 5.00 GiB (1280 extents) to 10.00 GiB (2560 extents). Logical volume var successfully resized
As you can see we have increased the logical volume /dev/centos/var by 5GB, currently it is already 5GB so this will increase it to total of 10GB.
You can do the same with below command.
# lvextend -L 10G /dev/centos/var
As this is what was specified with no +.
Alternatively if you instead want to just use all free space in the volume group rather than specifying a size to increase to, run below command
# lvextend -l +100%FREE /dev/centos/var
Verify the extended LV using lvdisplay command shown below.
# vgdisplay --- Logical volume --- LV Path /dev/centos/var LV Name var VG Name centos LV UUID 7PNgg2-ZmnG-a26g-zRoT-PRVM-RDc1-oq6J4M LV Write Access read/write LV Creation host, time CentOS7, 2015-04-16 07:50:25 +1000 LV Status available # open 0 LV Size 10.00 GiB Current LE 2560 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 8192 Block device 253:2
Now that the logical volume has been extended, we can resize the file system. This will extend the file system so that it takes up the newly created space inside the logical volume. The command may differ depending on the type of file system you are using.
# resize2fs /dev/centos/var
# xfs_growfs /dev/centos/var
After resizing the file system the space should be ready to use. We can check disk space using df command.
# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/centos-root 9.8G 1.4G 8.5G 14% / devtmpfs 908M 0 908M 0% /dev tmpfs 914M 0 914M 0% /dev/shm tmpfs 914M 8.6M 905M 1% /run tmpfs 914M 0 914M 0% /sys/fs/cgroup /dev/sda1 497M 96M 402M 20% /boot /dev/mapper/centos-var 10G 33M 10G 1% /mnt
Above I have run a ‘mount /dev/centos/var /mnt’ to mount the logical volume to /mnt, as shown above /mnt is correctly reporting a size of 10G.