Skip disk compaction for plain disks

builder/parallels/iso/builder.go

@@ -114,6 +114,12 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 			errs, errors.New("disk_type can only be expand, or plain"))
 	}
 
+	if b.config.DiskType == "plain" && !b.config.SkipCompaction {
+		b.config.SkipCompaction = true
+		warnings = append(warnings,
+			"'skip_compaction' is enforced to be true for plain disks.")
+	}
+
 	if b.config.HardDriveInterface != "ide" && b.config.HardDriveInterface != "sata" && b.config.HardDriveInterface != "scsi" {
 		errs = packer.MultiErrorAppend(
 			errs, errors.New("hard_drive_interface can only be ide, sata, or scsi"))

builder/parallels/iso/builder_test.go

@@ -134,7 +134,7 @@ func TestBuilderPrepare_DiskType(t *testing.T) {
 	var b Builder
 	config := testConfig()
 
-	// Test a default boot_wait
+	// Test a default disk_type
 	delete(config, "disk_type")
 	warns, err := b.Prepare(config)
 	if len(warns) > 0 {
@@ -159,8 +159,21 @@ func TestBuilderPrepare_DiskType(t *testing.T) {
 		t.Fatal("should have error")
 	}
 
-	// Test with a good
+	// Test with plain disk with wrong setting for compaction
 	config["disk_type"] = "plain"
+	config["skip_compaction"] = false
+	b = Builder{}
+	warns, err = b.Prepare(config)
+	if len(warns) == 0 {
+		t.Fatalf("should have warning")
+	}
+	if err != nil {
+		t.Fatalf("should not have error: %s", err)
+	}
+
+	// Test with plain disk with correct setting for compaction
+	config["disk_type"] = "plain"
+	config["skip_compaction"] = true
 	b = Builder{}
 	warns, err = b.Prepare(config)
 	if len(warns) > 0 {
@@ -169,6 +182,7 @@ func TestBuilderPrepare_DiskType(t *testing.T) {
 	if err != nil {
 		t.Fatalf("should not have error: %s", err)
 	}
+
 }
 
 func TestBuilderPrepare_HardDriveInterface(t *testing.T) {

website/source/docs/builders/parallels-iso.html.md

@@ -110,7 +110,8 @@ builder.
     image file is small initially and grows in size as you add data to it, and
     `plain` (plain disk) that the image file has a fixed size from the moment it
     is created (i.e the space is allocated for the drive fully). Plain disks
-    perform faster than expanding disks.
+    perform faster than expanding disks. `skip_compaction` will be set to true
+    automatically for plain disks.
 
 -   `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
@@ -225,9 +226,10 @@ builder.
     "5m", or five minutes.
 
 -   `skip_compaction` (boolean) - Virtual disk image is compacted at the end of
-    the build process using `prl_disk_tool` utility. In certain rare cases, this
-    might corrupt the resulting disk image. If you find this to be the case,
-    you can disable compaction using this configuration value.
+    the build process using `prl_disk_tool` utility (except for the case that
+    `disk_type` is set to `plain`). In certain rare cases, this might corrupt
+    the resulting disk image. If you find this to be the case, you can disable
+    compaction using this configuration value.
 
 -   `vm_name` (string) - This is the name of the PVM directory for the new
     virtual machine, without the file extension. By default this is