feat: add disk_format config with post-export disk conversion

builder/virtualbox/common/step_export.go

@@ -6,6 +6,7 @@ package common
 import (
 	"context"
 	"fmt"
+	"os"
 	"path/filepath"
 	"strings"
 
@@ -14,12 +15,9 @@ import (
 )
 
 // This step cleans up forwarded ports and exports the VM to an OVF.
-//
-// Uses:
-//
-// Produces:
-//
-//	exportPath string - The path to the resulting export.
+// When DiskFormat is set to a non-VMDK format (e.g. VDI), the exported
+// VMDK is converted to the requested format after export, and the OVF
+// references are updated accordingly.
 type StepExport struct {
 	Format         string
 	OutputDir      string
@@ -28,6 +26,7 @@ type StepExport struct {
 	Bundling       VBoxBundleConfig
 	SkipNatMapping bool
 	SkipExport     bool
+	DiskFormat     string
 }
 
 func (s *StepExport) Run(ctx context.Context, state multistep.StateBag) multistep.StepAction {
@@ -89,9 +88,82 @@ func (s *StepExport) Run(ctx context.Context, state multistep.StateBag) multiste
 		return multistep.ActionHalt
 	}
 
+	// If a non-VMDK disk format is requested, convert the exported VMDK
+	// to the requested format and update the OVF references.
+	diskFormat := strings.ToUpper(s.DiskFormat)
+	if diskFormat != "" && diskFormat != "VMDK" {
+		if err := s.convertExportedDisk(driver, ui, diskFormat); err != nil {
+			state.Put("error", err)
+			ui.Error(err.Error())
+			return multistep.ActionHalt
+		}
+	}
+
 	state.Put("exportPath", outputPath)
 
 	return multistep.ActionContinue
 }
 
+// convertExportedDisk converts the VMDK produced by VBoxManage export
+// to the requested disk format (VDI, VHD) and updates the OVF file.
+func (s *StepExport) convertExportedDisk(driver Driver, ui packersdk.Ui, diskFormat string) error {
+	ext := strings.ToLower(diskFormat)
+
+	// Step A: Find the VMDK file in the output directory
+	pattern := filepath.Join(s.OutputDir, "*.vmdk")
+	matches, _ := filepath.Glob(pattern)
+	if len(matches) == 0 {
+		return fmt.Errorf("No VMDK file found in %s after export", s.OutputDir)
+	}
+	vmdkPath := matches[0]
+	vmdkBasename := filepath.Base(vmdkPath)
+
+	// Step B: Build the target disk path
+	vdiBasename := strings.TrimSuffix(vmdkBasename, ".vmdk") + "." + ext
+	vdiPath := filepath.Join(s.OutputDir, vdiBasename)
+
+	ui.Say(fmt.Sprintf("Converting exported disk from VMDK to %s...", diskFormat))
+	ui.Message(fmt.Sprintf("  %s -> %s", vmdkBasename, vdiBasename))
+
+	// Step C: Convert VMDK to requested format using VBoxManage clonemedium
+	err := driver.VBoxManage("clonemedium", "disk", vmdkPath, vdiPath, "--format", diskFormat)
+	if err != nil {
+		return fmt.Errorf("Error converting disk to %s: %s", diskFormat, err)
+	}
+
+	// Step D: Delete the VMDK
+	if err := os.Remove(vmdkPath); err != nil {
+		ui.Message(fmt.Sprintf("Warning: could not delete VMDK: %s", err))
+	}
+
+	// Step E: Read the OVF file
+	ovfPath := filepath.Join(s.OutputDir, s.OutputFilename+"."+s.Format)
+	ovfData, err := os.ReadFile(ovfPath)
+	if err != nil {
+		return fmt.Errorf("Error reading OVF file: %s", err)
+	}
+
+	// Step F: Replace VMDK references in OVF
+	// There are exactly 2 references:
+	//   1. File href: ovf:href="...disk001.vmdk"
+	//   2. Disk format URL: ovf:format="http://www.vmware.com/interfaces/specifications/vmdk.html#streamOptimized"
+	ovfContent := string(ovfData)
+	ovfContent = strings.ReplaceAll(ovfContent, vmdkBasename, vdiBasename)
+	ovfContent = strings.ReplaceAll(ovfContent,
+		"http://www.vmware.com/interfaces/specifications/vmdk.html#streamOptimized",
+		"http://www.virtualbox.org/VirtualBox/ExtPack/"+diskFormat)
+	// Also handle the OVF 0.9 sparse format URL
+	ovfContent = strings.ReplaceAll(ovfContent,
+		"http://www.vmware.com/specifications/vmdk.html#sparse",
+		"http://www.virtualbox.org/VirtualBox/ExtPack/"+diskFormat)
+
+	// Step G: Write the OVF file back
+	if err := os.WriteFile(ovfPath, []byte(ovfContent), 0644); err != nil {
+		return fmt.Errorf("Error writing updated OVF file: %s", err)
+	}
+
+	ui.Say(fmt.Sprintf("Disk converted to %s successfully.", diskFormat))
+	return nil
+}
+
 func (s *StepExport) Cleanup(state multistep.StateBag) {}

builder/virtualbox/iso/builder.go

@@ -11,6 +11,7 @@ import (
 	"errors"
 	"fmt"
 	"regexp"
+	"strings"
 
 	"github.com/hashicorp/hcl/v2/hcldec"
 	"github.com/hashicorp/packer-plugin-sdk/bootcommand"
@@ -105,6 +106,10 @@ type Config struct {
 	// ostypes. Setting the correct value hints to VirtualBox how to optimize
 	// the virtual hardware to work best with that operating system.
 	GuestOSType string `mapstructure:"guest_os_type" required:"false"`
+	// The format of the virtual disk to create. Valid values are VDI, VMDK,
+	// and VHD. Defaults to VDI. VDI supports discard/compact operations.
+	// VMDK is the OVF standard. VHD is used by Hyper-V.
+	DiskFormat string `mapstructure:"disk_format" required:"false"`
 	// When this value is set to true, a VDI image will be shrunk in response
 	// to the trim command from the guest OS. The size of the cleared area must
 	// be at least 1MB. Also set hard_drive_nonrotational to true to enable
@@ -257,6 +262,16 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, []string, error) {
 		b.config.DiskSize = 40000
 	}
 
+	if b.config.DiskFormat == "" {
+		b.config.DiskFormat = "VDI"
+	}
+	b.config.DiskFormat = strings.ToUpper(b.config.DiskFormat)
+	switch b.config.DiskFormat {
+	case "VDI", "VMDK", "VHD":
+	default:
+		errs = packersdk.MultiErrorAppend(errs, fmt.Errorf("invalid disk_format '%s', must be VDI, VMDK, or VHD", b.config.DiskFormat))
+	}
+
 	if b.config.HardDriveInterface == "" {
 		b.config.HardDriveInterface = "ide"
 	}
@@ -492,6 +507,7 @@ func (b *Builder) Run(ctx context.Context, ui packersdk.Ui, hook packersdk.Hook)
 			Bundling:       b.config.VBoxBundleConfig,
 			SkipNatMapping: b.config.SkipNatMapping,
 			SkipExport:     b.config.SkipExport,
+			DiskFormat:     b.config.DiskFormat,
 		},
 	}
 

builder/virtualbox/iso/step_create_disk.go

@@ -25,7 +25,7 @@ func (s *stepCreateDisk) Run(ctx context.Context, state multistep.StateBag) mult
 	driver := state.Get("driver").(vboxcommon.Driver)
 	ui := state.Get("ui").(packersdk.Ui)
 	vmName := state.Get("vmName").(string)
-	format := "VDI"
+	format := config.DiskFormat
 
 	// The main disk and additional disks
 	diskFullPaths := []string{}