Increase the size of a Redhat 6.5 LVM disk in virtual machine Hyper-V

Increase the size of a Redhat 6.5 LVM disk in virtual machine Hyper-V

1. Introduction:

This post will show you how to increase the disk space for a Hyper-v virtual machine running Linux that is using logical volume manager (LVM). First we need to increase the size of the actual disk on the Hyper-v virtual machine. Once this is complete we will get into the virtual machine and make the changes through the operating system in order to take advantage of the additional space that has been provided by the hard drive being extended. This will involve creating a new partition with the new space, expanding the volume group and logical group, then resizing the file system.

Important Note: follow the commands and the screenshot.

2. Identifying the partition type:

we will first confirm that our partition type is actually Linux LVM by running the below command.

fdisk -l

Below is the disk information showing that our initial setup only has the one 60GB disk currently, which is under the logical volume named /dev/mapper/vg_redhatserver-lv_root  this is what we will be expanding with the new disk.

3. Increasing the virtual hard disk:

First we increase the allocated disk space on the virtual machine itself. This is done by getting to 'Hyper-v Manager', in the right side click on 'Edit Disk

Choose the virtual machine disk

Select 'Expand'

Specify the size you want to expand. In this example the current size is 60GB so will increase it to 100GB

Click 'Finish'

4. Detect the new disk space:

A screenshot after performing this and confirming that the new space is displaying.

5. Partition the new disk space:

As outlined in the previous step the disk in my example that I am working with is /dev/sda. use 'fdisk' to create a new primary partition to make use of the new expanded disk space.

fdisk /dev/sda

Using fdisk to create a new partition, 'n' was selected for adding a new partition.

'p' is selected as we are making a primary partition.

As we already have /dev/sda1 and /dev/sda2 as shown in previous step, I will use '3' for this new partition which will be created as /dev/sda3

Press enter twice above as by default the first and last cylinders of the unallocated space should be correct. After this the partition is then ready.

't' is selected to change to a partition’s system ID, in this case we change to '3' which is the one we just created.

The hex code '8e' was entered as this is the code for a Linux LVM which is what we want this partition to be

'w' is used to write the table to disk and exit, basically all the changes that have been done will be saved and then you will be exited from fdisk.

A screenshot for all commands

Checking the partition /dev/sda3

That’s all for partitioning, we now have a new partition which is making use of the previously unallocated disk space from the increase in Hyper-v.

6. Increasing the logical volume:

Launch pvcreate command which creates a physical volume for later use by the logical volume manager (LVM). In this case the physical volume will be our new /dev/sda3 partition.

root@redhat-server:~# pvcreate /dev/sda3
  Device /dev/sda3 not found (or ignored by filtering).

In order to get around this you can either reboot, as in this instance the disk does not appear to be there correctly despite showing in “fdisk -l”. After a reboot use the same command which will succeed.

After a reboot

Next we need to confirm the name of the current volume group using the vgdisplay command. vgdisplay provides lots of information on the volume group.

root@redhat-server:~# vgdisplay
  --- Volume group ---
  VG Name               Mega
...
VG Size               59.51GiB 

Now we extend the 'vg_redhatserver' volume group by adding in the physical volume of /dev/sda3 which we created using the pvcreate command earlier.

root@redhat-server:~# vgextend Mega /dev/sda3

Using the 'pvscan' command we scan all disks for physical volumes, this should confirm the original /dev/sda2 partition and the newly created physical volume /dev/sda3

root@redhat-server:~# pvscan

Increase the logical volume which basically means we will be taking our original logical volume and extending it over our new partition/physical volume of /dev/sda3.
Confirm the path of the logical volume using 'lvdisplay'.

root@redhat-server:~# lvdisplay

The logical volume is then extended using the 'lvextend' command.

root@redhat-server:~# lvextend /dev/vg_redhatserver/lv_root /dev/sda3

The final step which is to resize the file system so that it can take advantage of this additional space, this is done using the 'resize2fs' command for ext based file systems. It took about 30 seconds or less depending to the disk's speed.

root@redhat-server:~# resize2fs /dev/vg_redhatserver/lv_root

Now with the 'df' command we can see that the total available disk space has been increased.