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efi_create.go
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/
efi_create.go
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// The following example will create a fully bootable EFI disk image. It assumes you have a bootable EFI file (any modern Linux kernel compiled with `CONFIG_EFI_STUB=y` will work) available.
package examples
import (
"fmt"
"log"
"os"
diskfs "github.com/diskfs/go-diskfs"
diskpkg "github.com/diskfs/go-diskfs/disk"
"github.com/diskfs/go-diskfs/filesystem"
"github.com/diskfs/go-diskfs/partition/gpt"
)
func CreateEfi(diskImg string) {
var (
espSize int64 = 100 * 1024 * 1024 // 100 MB
diskSize int64 = espSize + 4*1024*1024 // 104 MB
blkSize int64 = 512
partitionStart int64 = 2048
partitionSectors int64 = espSize / blkSize
partitionEnd int64 = partitionSectors - partitionStart + 1
)
// create a disk image
disk, err := diskfs.Create(diskImg, diskSize, diskfs.Raw, diskfs.SectorSizeDefault)
if err != nil {
log.Panic(err)
}
// create a partition table
table := &gpt.Table{
Partitions: []*gpt.Partition{
&gpt.Partition{Start: uint64(partitionStart), End: uint64(partitionEnd), Type: gpt.EFISystemPartition, Name: "EFI System"},
},
}
// apply the partition table
err = disk.Partition(table)
/*
* create an ESP partition with some contents
*/
kernel, err := os.ReadFile("/some/kernel/file")
spec := diskpkg.FilesystemSpec{Partition: 1, FSType: filesystem.TypeFat32}
fs, err := disk.CreateFilesystem(spec)
// make our directories
err = fs.Mkdir("/EFI/BOOT")
rw, err := fs.OpenFile("/EFI/BOOT/BOOTX64.EFI", os.O_CREATE|os.O_RDWR)
n, err := rw.Write(kernel)
if err != nil {
log.Panic(err)
}
fmt.Printf("wrote %d bytes\n", n)
}