techne/qcow2.org

#+title: QCOW2
#+setupfile: ../org-templates/page.org

** Mount qcow2 image
Enable NBD on the host:
#+begin_src shell
sudo modprobe nbd max_part=8
#+end_src

Connect qcow2 image as a network block device:
#+begin_src shell
sudo qemu-nbd --connect=/dev/nbd0 /path/to/image.qcow2
#+end_src

Find the VM's partitions:
#+begin_src shell
sudo fdisk /dev/nbd0 -l
#+end_src

Mount the partition from the VM:
#+begin_src shell
sudo mount /dev/nbd0p3 /mnt/point
#+end_src

To unmount:
#+begin_src shell
sudo umount /mnt/point
sudo qemu-nbd --disconnect /dev/nbd0
sudo rmmod nbd
#+end_src

** Resize qcow2 image
Install guestfs-tools (required for virt-resize command):
#+begin_src shell
sudo dnf install -y guestfs-tools
sudo apt install -y guestfs-tools libguestfs-tools
#+end_src

To resize qcow2 images, you'll have to create a new qcow2 image with the size you want, then use ~virt-resize~ on the old qcow2 image to the new one.

You'll need to know the root partition within the old qcow2 image.

Create a new qcow2 image with the size you want:
#+begin_src shell
qemu-img create -f qcow2 -o preallocation=metadata newdisk.qcow2 100G
#+end_src

Now resize the old one to the new one:
#+begin_src shell
virt-resize --expand /dev/vda3 olddisk.qcow2 newdisk.qcow2
#+end_src

Once you boot into the new qcow2 image, you'll probably have to adjust the size of the logical volume if it has LVM:
#+begin_src shell
sudo lvresize -l +100%FREE /dev/mapper/sysvg-root
#+end_src

Then resize the XFS root partition within the logical volume:
#+begin_src shell
sudo xfs_grow /dev/mapper/sysvg-root
#+end_src