Add support for building QEMU images from pre-existing image files

If the `disk_image` parameter is set to true treat the ISO location
as the source of the disk image, copy it to the destination,
resize and boot it.

builder/qemu/builder.go

@@ -61,6 +61,7 @@ type config struct {
 	FloppyFiles     []string   `mapstructure:"floppy_files"`
 	Format          string     `mapstructure:"format"`
 	Headless        bool       `mapstructure:"headless"`
+	DiskImage       bool       `mapstructure:"disk_image"`
 	HTTPDir         string     `mapstructure:"http_directory"`
 	HTTPPortMin     uint       `mapstructure:"http_port_min"`
 	HTTPPortMax     uint       `mapstructure:"http_port_max"`
@@ -396,6 +397,8 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 			Files: b.config.FloppyFiles,
 		},
 		new(stepCreateDisk),
+		new(stepCopyDisk),
+		new(stepResizeDisk),
 		new(stepHTTPServer),
 		new(stepForwardSSH),
 		new(stepConfigureVNC),

builder/qemu/step_copy_disk.go

@@ -0,0 +1,45 @@
+package qemu
+
+import (
+	"fmt"
+	"github.com/mitchellh/multistep"
+	"github.com/mitchellh/packer/packer"
+	"path/filepath"
+	"strings"
+)
+
+// This step copies the virtual disk that will be used as the
+// hard drive for the virtual machine.
+type stepCopyDisk struct{}
+
+func (s *stepCopyDisk) Run(state multistep.StateBag) multistep.StepAction {
+	config := state.Get("config").(*config)
+	driver := state.Get("driver").(Driver)
+	isoPath := state.Get("iso_path").(string)
+	ui := state.Get("ui").(packer.Ui)
+	path := filepath.Join(config.OutputDir, fmt.Sprintf("%s.%s", config.VMName,
+		strings.ToLower(config.Format)))
+
+	command := []string{
+		"convert",
+		"-f", config.Format,
+		isoPath,
+		path,
+	}
+
+    if config.DiskImage == false {
+        return multistep.ActionContinue
+    }
+
+	ui.Say("Copying hard drive...")
+	if err := driver.QemuImg(command...); err != nil {
+		err := fmt.Errorf("Error creating hard drive: %s", err)
+		state.Put("error", err)
+		ui.Error(err.Error())
+		return multistep.ActionHalt
+	}
+
+	return multistep.ActionContinue
+}
+
+func (s *stepCopyDisk) Cleanup(state multistep.StateBag) {}

builder/qemu/step_create_disk.go

@@ -26,6 +26,10 @@ func (s *stepCreateDisk) Run(state multistep.StateBag) multistep.StepAction {
 		fmt.Sprintf("%vM", config.DiskSize),
 	}
 
+    if config.DiskImage == true {
+        return multistep.ActionContinue
+    }
+
 	ui.Say("Creating hard drive...")
 	if err := driver.QemuImg(command...); err != nil {
 		err := fmt.Errorf("Error creating hard drive: %s", err)

builder/qemu/step_resize_disk.go

@@ -0,0 +1,43 @@
+package qemu
+
+import (
+	"fmt"
+	"github.com/mitchellh/multistep"
+	"github.com/mitchellh/packer/packer"
+	"path/filepath"
+	"strings"
+)
+
+// This step resizes the virtual disk that will be used as the
+// hard drive for the virtual machine.
+type stepResizeDisk struct{}
+
+func (s *stepResizeDisk) Run(state multistep.StateBag) multistep.StepAction {
+	config := state.Get("config").(*config)
+	driver := state.Get("driver").(Driver)
+	ui := state.Get("ui").(packer.Ui)
+	path := filepath.Join(config.OutputDir, fmt.Sprintf("%s.%s", config.VMName,
+		strings.ToLower(config.Format)))
+
+	command := []string{
+		"resize",
+		path,
+		fmt.Sprintf("%vM", config.DiskSize),
+	}
+
+    if config.DiskImage == false {
+        return multistep.ActionContinue
+    }
+
+	ui.Say("Resizing hard drive...")
+	if err := driver.QemuImg(command...); err != nil {
+		err := fmt.Errorf("Error creating hard drive: %s", err)
+		state.Put("error", err)
+		ui.Error(err.Error())
+		return multistep.ActionHalt
+	}
+
+	return multistep.ActionContinue
+}
+
+func (s *stepResizeDisk) Cleanup(state multistep.StateBag) {}