Fix: resize GuestOS disk #3437

songponssw · 2025-04-17T05:34:11Z

Try to fix: #1448

How Lima edit disk

The limactl edit updates the disk value to the store. It does not resize disk image. Users have to manually resize by qemu-img
Does not support --shrink (fails to start instance)

What I did

create a limactl disk add command to add an existing qcow2 disk to Lima.
To update GuestOS disk, before start instance, It adds a diffdisk of the instance to Lima, resize, and delete.

cmd/limactl/disk.go

AkihiroSuda · 2025-04-17T08:59:03Z

pkg/store/instance.go

+func (inst *Instance) ResizeGuestOSDisk() error {
+	fName := filepath.Join(inst.Dir, filenames.DiffDisk)
+
+	cmd := exec.Command("limactl", "disk", "add", inst.Name, "--filename", fName)


limactl shouldn't invoke limactl itself unless it is inevitable or there is a significant benefit

Signed-off-by: Songpon Srisawai <songpon.ssw@gmail.com>

songponssw · 2025-04-25T10:57:57Z

This implementation works fine for increasing the disk size.
However, it returns an error when shrinking, as disk shrinking is not supported.

AkihiroSuda · 2025-05-06T13:53:35Z

Needs rebase

AkihiroSuda · 2025-05-06T13:54:05Z

cmd/limactl/edit.go

@@ -157,6 +157,12 @@ func editAction(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		return err
 	}
+
+	inst, err = store.Inspect(inst.Name)


The reason to inspect the instance twice should be explained as a code comment

AkihiroSuda · 2025-05-06T13:56:12Z

pkg/instance/start.go

+	format := string(img.Type())
+
+	if inst.Disk == diskSize {
+		logrus.Infof("diffDisk size does not changed")


This debug message can be removed

AkihiroSuda · 2025-05-07T05:00:48Z

pkg/instance/start.go

+		return errors.New("diffDisk: Shrinking is currently unavailable")
+	}
+
+	tmpDiskDir := filepath.Join(filenames.DisksDir, inst.Name+"-tmp")


DisksDir is dedicated for additional disks, and should not be used for the main disk

If that's the case, it would make sense to implement a separate ResizeDiffDisk() function specifically for resizing the diffDisk in the instance directory (e.g., ~/.lima/default/diffdisk)?

This implementation tries to reuse ResizeDataDisk(), which was originally intended for additional disks.

songponssw marked this pull request as ready for review April 17, 2025 05:34

songponssw marked this pull request as draft April 17, 2025 05:34