Table of Contents

+

KVM / QEMU Extend a virtual disk

Extend a virtual disk with simple partition schema

With the VM shut down directly extend the disk image on the host: 

qemu-img resize virtual_disk.qcow2 +10G

Load the network block device driver into the kernel and attach the disk to the host 

modprobe nbd
qemu-nbd -c /dev/nbd0 virtual_disk.qcow2

Use a partition manager (gParted …) to extend the partition

Disconnect the virtual disk from the host 

qemu-nbd -d /dev/nbd0

Start the VM and check if all is ok

Extend a virtual disk with LVM partitions

With the VM shut down directly extend the disk image on the host: 

qemu-img resize virtual_disk.qcow2 +10G

Start the VM and login.
As root or sudo: 

lsblk
NAME                MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sr0                  11:0    1  1024M  0 rom  
vda                 252:0    0   260G  0 disk 
├─vda1              252:1    0   600M  0 part /boot/efi
├─vda2              252:2    0     1G  0 part /boot
└─vda3              252:3    0 208.4G  0 part 
  ├─rhel_rhel8-root 253:0    0   180G  0 lvm  /
  ├─rhel_rhel8-swap 253:1    0     4G  0 lvm  [SWAP]
  └─rhel_rhel8-home 253:2    0  24.4G  0 lvm  /home

This shows the LVM partitions are on device vda, partition 3 (vda3)

pvs
  PV         VG         Fmt  Attr PSize   PFree
  /dev/vda3  rhel_rhel8 lvm2 a--  258.41g    0

The virtual device is /dev/vda3 and the volume group is rhel_rehl8

Claim the free disk space for partition 3 

growpart /dev/vda 3
pvresize /dev/vda3

… and finally claim the available space for the root partition: 

lvextend -r -l +100%FREE /dev/rhel_rhel8/root

Check if all went well: 

lsblk
NAME                MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sr0                  11:0    1  1024M  0 rom  
vda                 252:0    0   260G  0 disk 
├─vda1              252:1    0   600M  0 part /boot/efi
├─vda2              252:2    0     1G  0 part /boot
└─vda3              252:3    0 258.4G  0 part 
  ├─rhel_rhel8-root 253:0    0   230G  0 lvm  /
  ├─rhel_rhel8-swap 253:1    0     4G  0 lvm  [SWAP]
  └─rhel_rhel8-home 253:2    0  24.4G  0 lvm  /home

vda3 grew from 208.4 GB to 258.4 GB and the space was added to rhel_rhel8-root: it grew from 180 GB to 230 GB.

Done.