core: make qemu an optional dependency

Signed-off-by: Abiola Ibrahim <git@abiosoft.com>

Author: abiosoft

cmd/start.go

@@ -290,6 +290,10 @@ func setConfigDefaults(conf *config.Config) {
 	// handle macOS virtualization.framework transition
 	if conf.VMType == "" {
 		conf.VMType = defaultVMType
+		// if on macOS with no qemu, use vz
+		if err := util.AssertQemuImg(); err != nil && util.MacOS13OrNewer() {
+			conf.VMType = "vz"
+		}
 	}
 
 	if conf.MountType == "" {

config/configmanager/configmanager.go

@@ -71,6 +71,11 @@ func ValidateConfig(c config.Config) error {
 	if _, ok := validVMTypes[c.VMType]; !ok {
 		return fmt.Errorf("invalid vmType: '%s'", c.VMType)
 	}
+	if c.VMType == "qemu" {
+		if err := util.AssertQemuImg(); err != nil {
+			return fmt.Errorf("cannot use vmType: '%s', error: %w", c.VMType, err)
+		}
+	}
 
 	return nil
 }

environment/vm/lima/lima.go

@@ -319,6 +319,11 @@ func (l *limaVM) syncDiskSize(ctx context.Context, conf config.Config) config.Co
 			return false
 		}
 
+		if err := util.AssertQemuImg(); err != nil {
+			log.Warnln(fmt.Errorf("unable to resize disk: %w", err))
+			return false
+		}
+
 		sizeStr := fmt.Sprintf("%dG", conf.Disk)
 		args := []string{"qemu-img", "resize"}
 		disk := limautil.ColimaDiffDisk(config.CurrentProfile().ID)

environment/vm/lima/limautil/image.go

@@ -12,6 +12,7 @@ import (
 	"github.com/abiosoft/colima/environment"
 	"github.com/abiosoft/colima/environment/host"
 	"github.com/abiosoft/colima/environment/vm/lima/limaconfig"
+	"github.com/abiosoft/colima/util"
 	"github.com/abiosoft/colima/util/downloader"
 	"github.com/sirupsen/logrus"
 )
@@ -32,7 +33,7 @@ func ImageCached(arch environment.Arch, runtime string) (limaconfig.File, bool)
 
 	image := diskImageFile(downloader.CacheFilename(img.Location))
 
-	img.Location = image.Raw()
+	img.Location = image.Location()
 	img.Digest = ""
 
 	return img, image.Generated()
@@ -65,8 +66,18 @@ func DownloadImage(arch environment.Arch, runtime string) (f limaconfig.File, er
 	if err != nil {
 		return f, err
 	}
+
+	diskImage := diskImageFile(qcow2)
+
+	// if qemu-img is missing, ignore raw conversion
+	if err := util.AssertQemuImg(); err != nil {
+		img.Location = diskImage.String()
+		img.Digest = "" // remove digest
+		return img, nil
+	}
+
 	// convert from qcow2 to raw
-	raw, err := qcow2ToRaw(host, diskImageFile(qcow2))
+	raw, err := qcow2ToRaw(host, diskImage)
 	if err != nil {
 		return f, err
 	}
@@ -160,6 +171,14 @@ type diskImageFile string
 func (d diskImageFile) String() string { return strings.TrimSuffix(string(d), ".raw") }
 func (d diskImageFile) Raw() string    { return d.String() + ".raw" }
 func (d diskImageFile) Generated() bool {
-	stat, err := os.Stat(d.Raw())
+	stat, err := os.Stat(d.Location())
 	return err == nil && !stat.IsDir()
 }
+
+// Location returns the expected location of the image based on availability of qemu.
+func (d diskImageFile) Location() string {
+	if err := util.AssertQemuImg(); err == nil {
+		return d.Raw()
+	}
+	return d.String()
+}

util/qemu.go

@@ -0,0 +1,16 @@
+package util
+
+import (
+	"fmt"
+	"os/exec"
+)
+
+// AssertQemuImg checks if qemu-img is available.
+func AssertQemuImg() error {
+	cmd := "qemu-img"
+	if _, err := exec.LookPath(cmd); err != nil {
+		return fmt.Errorf("%s not found, run 'brew install %s' to install", cmd, "qemu")
+	}
+
+	return nil
+}