disk: add support for selecting partition table type

Follow-up to the previous commit. Translates the given partition table
type from a blueprint to the actual partition table.

pkg/disk/partition_table.go

@@ -1232,15 +1232,24 @@ func NewCustomPartitionTable(customizations *blueprint.DiskCustomization, option
 
 	pt := &PartitionTable{}
 
-	// TODO: Handle partition table type in customizations
-	switch options.PartitionTableType {
-	case PT_GPT, PT_DOS:
-		pt.Type = options.PartitionTableType
-	case PT_NONE:
-		// default to "gpt"
+	switch customizations.Type {
+	case "dos":
+		pt.Type = PT_DOS
+	case "gpt":
 		pt.Type = PT_GPT
+	case "":
+		// partition table type not specified, determine the default
+		switch options.PartitionTableType {
+		case PT_GPT, PT_DOS:
+			pt.Type = options.PartitionTableType
+		case PT_NONE:
+			// default to "gpt"
+			pt.Type = PT_GPT
+		default:
+			return nil, fmt.Errorf("%s invalid partition table type enum value: %d", errPrefix, options.PartitionTableType)
+		}
 	default:
-		return nil, fmt.Errorf("%s invalid partition table type enum value: %d", errPrefix, options.PartitionTableType)
+		return nil, fmt.Errorf("%s invalid partition table type: %s", errPrefix, customizations.Type)
 	}
 
 	// add any partition(s) that are needed for booting (like /boot/efi)

pkg/disk/partition_table_test.go

@@ -1131,11 +1131,13 @@ func TestNewCustomPartitionTable(t *testing.T) {
 
 	testCases := map[string]testCase{
 		"dos-hybrid": {
-			customizations: nil,
+			customizations: &blueprint.DiskCustomization{
+				Type: "dos", // overrides the default option
+			},
 			options: &disk.CustomPartitionTableOptions{
 				DefaultFSType:      disk.FS_XFS,
 				BootMode:           platform.BOOT_HYBRID,
-				PartitionTableType: disk.PT_DOS,
+				PartitionTableType: disk.PT_GPT,
 			},
 			expected: &disk.PartitionTable{
 				Type: disk.PT_DOS,
@@ -1580,6 +1582,7 @@ func TestNewCustomPartitionTable(t *testing.T) {
 		},
 		"plain+": {
 			customizations: &blueprint.DiskCustomization{
+				Type: "gpt", // overrides the default option
 				Partitions: []blueprint.PartitionCustomization{
 					{
 						MinSize: 50 * datasizes.MiB,
@@ -1609,7 +1612,7 @@ func TestNewCustomPartitionTable(t *testing.T) {
 			options: &disk.CustomPartitionTableOptions{
 				DefaultFSType:      disk.FS_EXT4,
 				BootMode:           platform.BOOT_HYBRID,
-				PartitionTableType: disk.PT_GPT,
+				PartitionTableType: disk.PT_DOS,
 				RequiredMinSizes:   map[string]uint64{"/": 3 * datasizes.GiB},
 			},
 			expected: &disk.PartitionTable{
@@ -2267,6 +2270,12 @@ func TestNewCustomPartitionTableErrors(t *testing.T) {
 			},
 			errmsg: `error generating partition table: invalid partition table type enum value: 100`,
 		},
+		"bad-pt-type-in-customizations": {
+			customizations: &blueprint.DiskCustomization{
+				Type: "toucan",
+			},
+			errmsg: `error generating partition table: unknown partition table type: toucan (valid: gpt, dos)`,
+		},
 	}
 
 	// we don't care about the rng for error tests

test/configs/partitioning-lvm.json

@@ -3,6 +3,7 @@
   "blueprint": {
     "customizations": {
       "disk": {
+        "type": "dos",
         "partitions": [
           {
             "mountpoint": "/data",