limactl disk: Do not use qemu-img for raw disks

Fix `limactl disk create` and `limactl disk resize` to use nativeimgutil
for creating and resizing disks using raw format.

There are special cases (using direct I/O on certain file systems) when
creating a raw image should be done with qemu-img, but these are not
relevant to lima on macOS.

With this change we have no dependency on qemu when using VZ instance.

This change does not fix the issue of default "qcow2" disk format.
Users must specify the disk format when creating additional disks for VZ
instance:

    limactl disk create --format raw

Unfinished:
- Needs tests for nativeimgutil and disk command

Fixes: #2853
Signed-off-by: Nir Soffer <[email protected]>

cmd/limactl/disk.go

@@ -9,6 +9,7 @@ import (
 	"text/tabwriter"
 
 	"github.com/docker/go-units"
+	"github.com/lima-vm/lima/pkg/nativeimgutil"
 	"github.com/lima-vm/lima/pkg/qemu"
 	"github.com/lima-vm/lima/pkg/store"
 	"github.com/sirupsen/logrus"
@@ -101,7 +102,13 @@ func diskCreateAction(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	if err := qemu.CreateDataDisk(diskDir, format, int(diskSize)); err != nil {
+	// qemu may not be available, use it only if needed.
+	if format == "raw" {
+		err = nativeimgutil.CreateRawDataDisk(diskDir, int(diskSize))
+	} else {
+		err = qemu.CreateDataDisk(diskDir, format, int(diskSize))
+	}
+	if err != nil {
 		rerr := os.RemoveAll(diskDir)
 		if rerr != nil {
 			err = errors.Join(err, fmt.Errorf("failed to remove a directory %q: %w", diskDir, rerr))
@@ -390,9 +397,17 @@ func diskResizeAction(cmd *cobra.Command, args []string) error {
 			}
 		}
 	}
-	if err := qemu.ResizeDataDisk(disk.Dir, disk.Format, int(diskSize)); err != nil {
+
+	// qemu may not be available, use it only if needed.
+	if disk.Format == "raw" {
+		err = nativeimgutil.ResizeRawDataDisk(disk.Dir, int(diskSize))
+	} else {
+		err = qemu.ResizeDataDisk(disk.Dir, disk.Format, int(diskSize))
+	}
+	if err != nil {
 		return fmt.Errorf("failed to resize disk %q: %w", diskName, err)
 	}
+
 	logrus.Infof("Resized disk %q (%q)", diskName, disk.Dir)
 	return nil
 }

pkg/nativeimgutil/nativeimgutil.go

@@ -2,21 +2,44 @@
 package nativeimgutil
 
 import (
+	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"os"
 	"path/filepath"
 
-	"github.com/containerd/continuity/fs"
+	containerdfs "github.com/containerd/continuity/fs"
 	"github.com/docker/go-units"
 	"github.com/lima-vm/go-qcow2reader"
 	"github.com/lima-vm/go-qcow2reader/convert"
 	"github.com/lima-vm/go-qcow2reader/image/qcow2"
 	"github.com/lima-vm/go-qcow2reader/image/raw"
 	"github.com/lima-vm/lima/pkg/progressbar"
+	"github.com/lima-vm/lima/pkg/store/filenames"
 	"github.com/sirupsen/logrus"
 )
 
+// CreateRawDataDisk creates an empty raw data disk.
+func CreateRawDataDisk(dir string, size int) error {
+	dataDisk := filepath.Join(dir, filenames.DataDisk)
+	if _, err := os.Stat(dataDisk); err == nil || !errors.Is(err, fs.ErrNotExist) {
+		return err
+	}
+	f, err := os.Create(dataDisk)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	return f.Truncate(int64(size))
+}
+
+// ResizeRawDataDisk resizes a raw data disk.
+func ResizeRawDataDisk(dir string, size int) error {
+	dataDisk := filepath.Join(dir, filenames.DataDisk)
+	return os.Truncate(dataDisk, int64(size))
+}
+
 // ConvertToRaw converts a source disk into a raw disk.
 // source and dest may be same.
 // ConvertToRaw is a NOP if source == dest, and no resizing is needed.
@@ -106,7 +129,7 @@ func ConvertToRaw(source, dest string, size *int64, allowSourceWithBackingFile b
 func convertRawToRaw(source, dest string, size *int64) error {
 	if source != dest {
 		// continuity attempts clonefile
-		if err := fs.CopyFile(dest, source); err != nil {
+		if err := containerdfs.CopyFile(dest, source); err != nil {
 			return fmt.Errorf("failed to copy %q into %q: %w", source, dest, err)
 		}
 	}