KVM - Extend a virtio disk online

Sometimes it turns out, your initial sizing of a VM might have been too small. While RAM and CPU can easily be extended, Disk, on the other hand, might be a different story but usually, the process is rather simple. This is how I tend to do extend a disk that is used by LVM.

First, resize the VM's disk on the hypervisor, note that this command is specific for KVM

 [archy@hyv01 ~]$ sudo virsh blockresize --domain repo.archyslife.lan --path /srv/kvm/vm-images/repo.archyslife.lan-disk1.qcow2 --size 250G  

You can verify your changes by running this command

 [root@hyv01 ~]# sudo virsh domblkinfo --domain repo.archyslife.lan --device vda --human  
 Capacity:    250.000 GiB  
 Allocation:   199.435 GiB  
 Physical:    250.000 GiB  

If you are using virtio (like me in this example), the disk should automatically be resized in the VM and you can continue to resize the partition or physical volume. If you're resizing a SATA / SAS / SCSI Disk, you'll have to make the VM rescan the device to make it detect the new size

 [root@repo ~]# echo 1 > /sys/class/block/sda/device/rescan  

Now onto the partitioning of the disk. Resizing can be done in a single command

 [root@repo ~]# pvresize /dev/vdX(y)  

where
X: the disk itself
y: the partition if using any

An example would look like this:

 [root@repo ~]# pvresize /dev/vda2  

You can now use the additional space as shown in the output of 'pvs' or 'vgs' for resizing.

Feel free to comment and / or suggest a topic.