Class: IgnitionDiskGenerator

Inherits:
Object
  • Object
show all
Defined in:
lib/vagrant-ignition/action/IgnitionDiskGenerator.rb

Overview

Note: gpt and gpt2 are the primary and secondary headers respectively

Class Method Summary collapse

Class Method Details

.create_disk(ignition_name, config_drive) ⇒ Object 



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# File 'lib/vagrant-ignition/action/IgnitionDiskGenerator.rb', line 13

def self.create_disk(ignition_name, config_drive)
  # Constants
  @first_usable_lba  = 2048
  @gpt_entrysize     = 128
  @gpt_max_entries   = 128
  gpt_lba            = 1
  arr_lba            = 2
  lba_size           = 512
  pmbr_length        = lba_size
  @gpt_length        = lba_size
  arr_length         = @gpt_max_entries * @gpt_entrysize
  minimum_disk_size  = 1536000                                                             # ~1.5M; there are issues with udev not registering the device if it is less than this...
  partitioner_reserved_space = (@first_usable_lba * lba_size) + (@gpt_length + arr_length) # this is space reserved by the partition tables and arrays
  part_label         = "Ignition Config Drive"
  part_label_encoded = part_label.encode("utf-16le").bytes
 
  ignition_conf = File.open(ignition_name, "r")
  contents = ignition_conf.sysread(File.size?(ignition_name))
  ignition_conf.close
  file_size_unrounded = contents.bytesize
  if file_size_unrounded < minimum_disk_size
    file_size = minimum_disk_size - partitioner_reserved_space
  elsif (file_size_unrounded % lba_size) != 0
    file_size = lba_size * ((file_size_unrounded / lba_size) + 1)
  else
    file_size = file_size_unrounded
  end
  drive_size = file_size + partitioner_reserved_space

  # Calculated variables
  drive_sectors    = drive_size / lba_size
  gpt2_lba         = drive_sectors - 1
  arr2_lba         = drive_sectors - 33
  # This is global as gen_gpt requires it
  @last_usable_lba = drive_sectors - 34

  ## START PMBR ##
  pmbr  = ("\0".bytes) * 446         # bootloader code
  pmbr += "\x00".bytes               # status code
  pmbr += "\x00\x01\x00".bytes       # first CHS (for a protective MBR, we can just use the min value)
  pmbr += "\xee".bytes               # partition type
  pmbr += "\xfe\xff\xff".bytes       # last CHS (for a protective MBR, we can just use the max value)
  pmbr += "\x01\x00\x00\x00".bytes   # first LBA of first partition
  pmbr += [gpt2_lba].pack('L').bytes # last LBA of first partition
  pmbr += ("\x00".bytes) * 48        # other partition data
  pmbr += "\x55\xaa".bytes           # MBR signature
  ## END PMBR ##

  ## START PART ##

  # UUID format on disk according to cgpt:
  # typedef struct {
  # UINT32 Data1;
  # UINT16 Data2;
  # UINT16 Data3;
  # UINT8 Data4[8];
  # } EFI_GUID;

  # Partition Type GUID is 0FC63DAF-8483-4772-8E79-3D69D8477DE4 (Linux Filesystem)
  part1  = [0x0FC63DAF].pack('L').bytes + [0x8483].pack('S').bytes + [0x4772].pack('S').bytes + [0x8E793D69D8477DE4].pack('Q').bytes.reverse!
  # Partition GUID is 99570A8A-F826-4EB0-BA4E-9DD72D55EA13
  part1 += [0x99570A8A].pack('L').bytes + [0xF826].pack('S').bytes + [0x4EB0].pack('S').bytes + [0xBA4E9DD72D55EA13].pack('Q').bytes.reverse!
  part1 += [@first_usable_lba].pack('Q').bytes                                                                # first LBA of first partition
  part1 += [@last_usable_lba].pack('Q').bytes                                                                 # last LBA of first partition
  part1 += "\0".bytes * 8                                                                                     # partition attributes
  part1 += part_label_encoded + ("\0".bytes * (72 - part_label_encoded.length))                               # partition name (length of 72 bytes, or 36 utf16le characters)
  part_others = "\0".bytes * (arr_length - part1.length)                                                      # other partition data
  part_arr = part1 + part_others
  part_extra_space = "\0".bytes * ((@first_usable_lba * lba_size) - (pmbr_length + @gpt_length + arr_length)) # this adds a buffer so that our partition starts at sector 2048
  part_full = part_arr + part_extra_space
  ## END PART ##


  ## START GPT ##
  gpt = gen_gpt(gpt_lba, gpt2_lba, arr_lba, part_arr)
  ## END GPT ##

  ## START GPT2 ##
  gpt2 = gen_gpt(gpt2_lba, gpt_lba, arr2_lba, part_arr)
  ## END GPT2 ##

  ## START DATA ##
  if file_size_unrounded < minimum_disk_size
    data = contents.bytes + ("\x00".bytes * (file_size - contents.bytesize))
  else
    data = contents.bytes + ("\x00".bytes * (lba_size - (file_size_unrounded % lba_size)))
  end
  ## END DATA ##

  device = pmbr + gpt + part_full + data + part1 + part_others + gpt2

  File.open(config_drive, 'wb' ) do |output|
    device.each do | byte |
      output.print byte.chr
    end
  end
end