THe cloud image is shipped as a qcow2 file. It has about 3 GB of usable space. I need more.

The Root FS for my Fedora43 Cloud image is a btrfs mounted on /dev/vda3.

First, stop the virtual machine. Then grow the Qcow2 image

qemu-img resize vms/Fedora-Cloud-Base-Generic-43-1.6.aarch64.qcow2 +50G

Start the virtual machine. Grow the partition

growpart /dev/vda3 1

finally resize the filesystem.

btrfs filesystem resize max /

Now the disk is 50G larger:

# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/vda3        53G  1.8G   51G   4% /