actually made a default boot partition

1 files changed, 88 insertions, 0 deletions

diff --git a/makeGptPartitions.go b/makeGptPartitions.go
new file mode 100644
index 0000000..d272e7d
--- /dev/null
+++ b/makeGptPartitions.go
@@ -0,0 +1,88 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	"go.wit.com/log"
+
+	"github.com/diskfs/go-diskfs"
+	"github.com/diskfs/go-diskfs/partition/gpt"
+)
+
+// make a default bootable GPT partition table
+func makeDefaultGPT(devname string) error {
+	// Open disk
+	// disk, err := diskfs.Open(devname, diskfs.ReadWrite)
+	disk, err := diskfs.Open(devname, diskfs.WithOpenMode(diskfs.ReadWrite))
+	if err != nil {
+		log.Errorf("Failed to open disk: %v\n", err)
+		return err
+	}
+
+	file, err := os.Open(devname)
+	if err != nil {
+		log.Errorf("Failed to open file for size: %v\n", err)
+		return err
+	}
+	defer file.Close()
+
+	// Determine disk size via Seek
+	sizeBytes, err := file.Seek(0, io.SeekEnd)
+	if err != nil {
+		log.Errorf("Failed to determine disk size: %v\n", err)
+		return err
+	}
+	sectorSize := int64(512)
+	totalSectors := uint64(sizeBytes / sectorSize)
+
+	// Setup partitions:
+	// Partition 1: BIOS boot, ~1MiB, starts at sector 2048
+	biosStart := uint64(2048)
+	biosSize := uint64(1 * 1024 * 1024) // bytes
+	biosSectors := biosSize / uint64(sectorSize)
+
+	// Partition 2: rest of the disk
+	rootStart := biosStart + biosSectors
+	rootSectors := totalSectors - rootStart
+
+	table := &gpt.Table{
+		LogicalSectorSize:  int(sectorSize),
+		PhysicalSectorSize: int(sectorSize),
+		ProtectiveMBR:      true,
+		Partitions: []*gpt.Partition{
+			{
+				Start: biosStart,
+				End:   biosStart + biosSectors - 1,
+				// Size is optional, but let's provide it
+				Size: biosSectors * uint64(sectorSize),
+				// GUID for BIOS boot partition (ESP-like GUID for BIOS boot)
+				Type: biosBootGUID,
+				Name: "bios_grub",
+			},
+			{
+				Start: rootStart,
+				End:   totalSectors - 1,
+				Size:  rootSectors * uint64(sectorSize),
+				// GUID for Linux filesystem partition
+				Type: linuxFSGUID,
+				Name: "root",
+			},
+		},
+	}
+
+	if err := disk.Partition(table); err != nil {
+		log.Errorf("Failed to write GPT partition table: %v", err)
+		return err
+	}
+
+	fmt.Println("Partition table successfully written!")
+	return nil
+}
+
+// GUID definitions (copied from GPT standard tables)
+const (
+	biosBootGUID = "21686148-6449-6E6F-744E-656564454649" // BIOS boot
+	linuxFSGUID  = "0FC63DAF-8483-4772-8E79-3D69D8477DE4" // Linux filesystem
+)