A macchina spenta, supponendo che l'immagine si chiami "macchina.qcow2":

root@hypervisor # qemu-img resize /var/lib/libvirt/images/macchina.qcow2 +10G

Poi bisogna usare resize2fs /dev/vda1, probabilmente rifacendo anche la partizione tramite fdisk. Un esempio:

root@orazio ~# fdisk /dev/vda -l
Disk /dev/vda: 60 GiB, 64424509440 bytes, 125829120 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 8E12E056-0076-4C2C-AC88-51E48D3D105E

Device       Start      End  Sectors  Size Type
/dev/vda1     2048  1050623  1048576  512M BIOS boot
/dev/vda2  1050624 50331614 49280991 23.5G Linux filesystem

Nota come Disk /dev/vda: 60 GiB ma /dev/vda2 ... 23.5G.

root@orazio ~# fdisk /dev/vda 

Welcome to fdisk (util-linux 2.38.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

This disk is currently in use - repartitioning is probably a bad idea.
It's recommended to umount all file systems, and swapoff all swap
partitions on this disk.


Command (m for help): d 
Partition number (1,2, default 2): 2

Partition 2 has been deleted.

Command (m for help): p
Disk /dev/vda: 60 GiB, 64424509440 bytes, 125829120 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 8E12E056-0076-4C2C-AC88-51E48D3D105E

Device     Start     End Sectors  Size Type
/dev/vda1   2048 1050623 1048576  512M BIOS boot

Command (m for help): n
Partition number (2-128, default 2): 
First sector (1050624-125829086, default 1050624): 
Last sector, +/-sectors or +/-size{K,M,G,T,P} (1050624-125829086, default 125827071): 

Created a new partition 2 of type 'Linux filesystem' and of size 59.5 GiB.
Partition #2 contains a ext4 signature.

Do you want to remove the signature? [Y]es/[N]o: n

Command (m for help): w

The partition table has been altered.
Syncing disks.

root@orazio ~# resize2fs /dev/vda2
resize2fs 1.47.0 (5-Feb-2023)
Filesystem at /dev/vda2 is mounted on /; on-line resizing required
old_desc_blocks = 3, new_desc_blocks = 8
The filesystem on /dev/vda2 is now 15597056 (4k) blocks long.

Potrebbe anche presentarsi questo errore:

root@orazio ~ # fdisk /dev/vda

Welcome to fdisk (util-linux 2.38.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

GPT PMBR size mismatch (50331647 != 125829119) will be corrected by write.
The backup GPT table is not on the end of the device. This problem will be corrected by write.
This disk is currently in use - repartitioning is probably a bad idea.
It's recommended to umount all file systems, and swapoff all swap
partitions on this disk.

In tal caso semplicemente riscrivi la tavola premendo w e ricomincia la procedura.