Sometimes it is required to add additional disk space to Virtual Machines. This is relatively straight forward from the hypervisor level. However the process for recognising and utilising that space will differ depending on the OS.  In this article I show the steps I have used in order to use a new hard disk that I have already added via vCenter to a Cent OS 7 VM.

Process

First we can run the below command to check the size of our attached disk.

lsblk

Partition the disk

In the above case the disk is listed as sdb.   I can now go ahead and partition this new drive.  Ensure that you are partitioning the correct drive:

fdisk /dev/sdb

There are many parameters that can be used within fdisk.  Below I listed out the procedure I used after running the command above.

• Press n to create the new partition
• Press p to define that this will be a primary partition
• Press 1 to establish a single partition
• Establish the value of the first sector which is 2048 by default
• Establish the value of the last sector which by default will be 41943039
• Save all the changes by pressing w

Once the partitioning has finished we can check the disk and partitions by running

fdisk -l

 

Format the new drive

The next step is to format the new hard drive with the desired file system using the command

mkfs.ext4 /dev/sdb1

Now we can mount the newly formatted disk. In my case I want to mount it to a new directory  called data

Mkdir /data
Mount /dev/sdb1 /data

In order to make the mount permanent I need to edit the fstab file. Firstly though I need to change the permissions on that file.

chmod 644 /etc/fstab

Now I can edit fstab

Sudo vi /etc/fstab

Within the file need to add the below line

/dev/sdb1/data ext4 defaults 0 0