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GUID Partition sectors
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GUID Partition sectors
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GUID Master Boot records are standard - as in Master Boot Record, but the partition table entry is rather different. The partition type, as described in byte 4 is set to 0xEE and the partition start, bytes 8-11 are normally set at 1. Sector 1 then has the complete partition information.
Sector 0
000000 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000010 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000020 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000030 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000040 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000050 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000060 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000070 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000080 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000090 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
0000A0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
0000B0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
0000C0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
0000D0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
0000E0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
0000F0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000100 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000110 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000120 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000130 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000140 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000150 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000160 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000170 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000180 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000190 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
0001A0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
0001B0 00 00 00 00 00 00 00 00 - 8C CC 51 6B 00 00 00 FE Qk
0001C0 FF FF EE FE FF FF 01 00 - 00 00 6F 59 1C 1D 00 00 oY
0001D0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
0001E0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
0001F0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 55 AA U
Sector 1 Partition table header
000000 45 46 49 20 50 41 52 54 - 00 00 01 00 5C 00 00 00 EFI PART \
000010 E6 CB B4 84 00 00 00 00 - 01 00 00 00 00 00 00 00 ˴
000020 6F 59 1C 1D 00 00 00 00 - 22 00 00 00 00 00 00 00 oY "
000030 4E 59 1C 1D 00 00 00 00 - 4E F1 2A 90 7A 65 97 49 NY N*ze—I
000040 86 05 CF CA DB 95 81 85 - 02 00 00 00 00 00 00 00 ە
000050 80 00 00 00 80 00 00 00 - B5 D7 E6 8B 00 00 00 00
000060 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
The rest of the sector is all zeros
0001E0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
0001F0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
The sector always starts with the string EFI PART followed by the version number (1) and record length (0x5c)
Offset 0x18 give the location of this sector (1)
Offset 0x20 is the offset of the spare EFI header (0x1d1c59ef)
Offset 0x28 is the start of the data area of the disk (0x22) normally just after the partition entries
Offset 0x48 start of partition entries, normally 2
Sector 2-33, Partition entries
00000000 16 E3 C9 E3 5C 0B B8 4D - 81 7D F9 2D F0 02 15 AE \ M}-
00000010 6E D9 3E F6 CE 0D B5 42 - A5 B8 8A 0B 10 6A 55 E3 n> B jU
00000020 22 00 00 00 00 00 00 00 - 21 00 04 00 00 00 00 00 " !
00000030 00 00 00 00 00 00 00 00 - 4D 00 69 00 63 00 72 00 M i c r
00000040 6F 00 73 00 6F 00 66 00 - 74 00 20 00 72 00 65 00 o s o f t r e
00000050 73 00 65 00 72 00 76 00 - 65 00 64 00 20 00 70 00 s e r v e d p
00000060 61 00 72 00 74 00 69 00 - 74 00 69 00 6F 00 6E 00 a r t i t i o n
00000070 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
00000080 A2 A0 D0 EB E5 B9 33 44 - 87 C0 68 B6 B7 26 99 C7 3Dh&
00000090 0A CD 32 5D 7E A5 35 48 - 9F B3 D7 0A A5 1F 77 EF 2]~5H w
000000A0 00 08 04 00 00 00 00 00 - FF 2F 51 5D 01 00 00 00 /Q]
000000B0 00 00 00 00 00 00 00 00 - 42 00 61 00 73 00 69 00 B a s i
000000C0 63 00 20 00 64 00 61 00 - 74 00 61 00 20 00 70 00 c d a t a p
000000D0 61 00 72 00 74 00 69 00 - 74 00 69 00 6F 00 6E 00 a r t i t i o n
000000E0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
000000F0 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
00000100 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00
EFI stands for Extensible Firmware Interface. EFI is designed to improve upon the existing Partition table design, which in particular has a 32 bit limit on sector numbers. 32 bit addressing will allow for 2TB of disk. Although this is not a problem at the moment, 1TB disks are becoming common, and 2TB are just being announced. The address fields are now 64 bit rather than 32 bit. This will give a few years grace in capacity.
Sector 2, and following sectors describe each partition type. Rather than a single byte, a GUID is used. Each partition is described by 0x80 (128) byte record, and so in the example above, there are two partitions. The first one
16 E3 C9 E3 5C 0B B8 4D - 81 7D F9 2D F0 02 15 AE
is a reseved microsoft partition It starst at sector 0x22 and has a length of 0x40021
The second partition is Microsoft Data, and can be a normal NTFS partition. The GUID is
A2 A0 D0 EB E5 B9 33 44 - 87 C0 68 B6 B7 26 99 C7
and the starting sector is 0x40800. The length is 0x15d512fff sectors, or about 2.9TB. It shows that this value is greater than 32 bits, and hence the requirement for the EFI partition data.
A GUID is a Globably Unique ID. These are numbers which should be unique. A series of such numbers have been defined for different types of disk partition, eg Microsoft Data Partition, Apple HFS+. There are also defined numbers for Linux, Solaris, HP-UX. CnW currently recognise a few of these, but the list will grow. The second 16 bytes of partition entry is a GUID for the specific drive. This can be treated as a unique partition serial number.