Merge pull request hashicorp#2748 from vtolstov/qcow2

add shrink step for qcow2 image format

builder/qemu/builder.go

@@ -88,6 +88,8 @@ type Config struct {
 	DiskSize        uint       `mapstructure:"disk_size"`
 	DiskCache       string     `mapstructure:"disk_cache"`
 	DiskDiscard     string     `mapstructure:"disk_discard"`
+	SkipCompaction  bool       `mapstructure:"skip_compaction"`
+	DiskCompression bool       `mapstructure:"disk_compression"`
 	FloppyFiles     []string   `mapstructure:"floppy_files"`
 	Format          string     `mapstructure:"format"`
 	Headless        bool       `mapstructure:"headless"`
@@ -242,6 +244,11 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 			errs, errors.New("invalid format, only 'qcow2' or 'raw' are allowed"))
 	}
 
+	if b.config.Format != "qcow2" {
+		b.config.SkipCompaction = true
+		b.config.DiskCompression = false
+	}
+
 	if _, ok := accels[b.config.Accelerator]; !ok {
 		errs = packer.MultiErrorAppend(
 			errs, errors.New("invalid accelerator, only 'kvm', 'tcg', 'xen', or 'none' are allowed"))
@@ -364,6 +371,7 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		},
 		new(common.StepProvision),
 		new(stepShutdown),
+		new(stepConvertDisk),
 	}
 
 	// Setup the state bag

builder/qemu/step_convert_disk.go

@@ -0,0 +1,67 @@
+package qemu
+
+import (
+	"fmt"
+	"path/filepath"
+
+	"github.com/mitchellh/multistep"
+	"github.com/mitchellh/packer/packer"
+
+	"os"
+)
+
+// This step converts the virtual disk that was used as the
+// hard drive for the virtual machine.
+type stepConvertDisk struct{}
+
+func (s *stepConvertDisk) Run(state multistep.StateBag) multistep.StepAction {
+	config := state.Get("config").(*Config)
+	driver := state.Get("driver").(Driver)
+	diskName := state.Get("disk_filename").(string)
+	ui := state.Get("ui").(packer.Ui)
+
+	if config.SkipCompaction && !config.DiskCompression {
+		return multistep.ActionContinue
+	}
+
+	name := diskName + ".convert"
+
+	sourcePath := filepath.Join(config.OutputDir, diskName)
+	targetPath := filepath.Join(config.OutputDir, name)
+
+	command := []string{
+		"convert",
+		"-q",
+	}
+
+	if config.DiskCompression {
+		command = append(command, "-c")
+	}
+
+	command = append(command, []string{
+		"-f", config.Format,
+		"-O", config.Format,
+		sourcePath,
+		targetPath,
+	}...,
+	)
+
+	ui.Say("Converting hard drive...")
+	if err := driver.QemuImg(command...); err != nil {
+		err := fmt.Errorf("Error converting hard drive: %s", err)
+		state.Put("error", err)
+		ui.Error(err.Error())
+		return multistep.ActionHalt
+	}
+
+	if err := os.Rename(targetPath, sourcePath); err != nil {
+		err := fmt.Errorf("Error moving converted hard drive: %s", err)
+		state.Put("error", err)
+		ui.Error(err.Error())
+		return multistep.ActionHalt
+	}
+
+	return multistep.ActionContinue
+}
+
+func (s *stepConvertDisk) Cleanup(state multistep.StateBag) {}

website/source/docs/builders/qemu.html.markdown

@@ -136,6 +136,12 @@ builder.
 -   `disk_size` (integer) - The size, in megabytes, of the hard disk to create
     for the VM. By default, this is 40000 (about 40 GB).
 
+-   `skip_compaction` (boolean) - Packer compacts the QCOW2 image using `qemu-img convert`.
+    Set this option to `true` to disable compacting. Defaults to `false`.
+
+-   `disk_compression` (boolean) - Apply compression to the QCOW2 disk file
+    using `qemu-img convert`. Defaults to `false`.
+
 -   `floppy_files` (array of strings) - A list of files to place onto a floppy
     disk that is attached when the VM is booted. This is most useful for
     unattended Windows installs, which look for an `Autounattend.xml` file on