On Thu, May 7, 2009 at 11:57 PM, Ashish SHUKLA <[email protected]> wrote:

> So GRUB is capable of booting from GPT disks, hmm...? In non GPT disks,
> GRUB embeds itself into the first 63 sectors of the disk. That code has
> the list of sectors, from where to load the 1.5stage and 2nd stage
> filesystem loaders, encoded at the time of installation of GRUB on the
> boot sector.


 GPT was a part of the EFI specification. But it's usable on non-EFI systems
as well.

On EFI systems, grub gets compiled as an EFI application. I haven't gotten
this to work yet (EFI on macbook pro requires a 64 bit grub.efi). On non-EFI
systems, there must be a mechanism similar to what you describe above.

This mechanism works on a Asus netbook, but not on a HP laptop. The first
two sectors look as follows:

fdisk:

Disk /dev/sdb: 320.0 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       38914   312571223+  ee  GPT

(parted) p
Model: WD 3200BEV External (scsi)
Disk /dev/sdb: 320GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name     Flags
 1      17.9kB  1074MB  1074MB  ext3                  boot
 2      1074MB  11.8GB  10.7GB  ext3
 3      11.8GB  12.9GB  1074MB  linux-swap
 4      12.9GB  32.9GB  20.0GB  fat32        primary  msftres

00000000  eb 48 90 00 00 00 00 00  00 00 00 00 00 00 00 00
|.H..............|
00000010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
|................|
*
00000030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 03 02
|................|
00000040  ff 00 00 80 1b 41 0c 00  00 08 fa 90 90 f6 c2 80
|.....A..........|
00000050  75 02 b2 80 ea 59 7c 00  00 31 c0 8e d8 8e d0 bc
|u....Y|..1......|
00000060  00 20 fb a0 40 7c 3c ff  74 02 88 c2 52 f6 c2 80  |.
..@|<.t...R...|
00000070  74 54 b4 41 bb aa 55 cd  13 5a 52 72 49 81 fb 55
|tT.A..U..ZRrI..U|
00000080  aa 75 43 a0 41 7c 84 c0  75 05 83 e1 01 74 37 66
|.uC.A|..u....t7f|
00000090  8b 4c 10 be 05 7c c6 44  ff 01 66 8b 1e 44 7c c7
|.L...|.D..f..D|.|
000000a0  04 10 00 c7 44 02 01 00  66 89 5c 08 c7 44 06 00
|....D...f.\..D..|
000000b0  70 66 31 c0 89 44 04 66  89 44 0c b4 42 cd 13 72
|pf1..D.f.D..B..r|
000000c0  05 bb 00 70 eb 7d b4 08  cd 13 73 0a f6 c2 80 0f
|...p.}....s.....|
000000d0  84 f0 00 e9 8d 00 be 05  7c c6 44 ff 00 66 31 c0
|........|.D..f1.|
000000e0  88 f0 40 66 89 44 04 31  d2 88 ca c1 e2 02 88 e8
|[email protected]........|
000000f0  88 f4 40 89 44 08 31 c0  88 d0 c0 e8 02 66 89 04
|[email protected]..|
00000100  66 a1 44 7c 66 31 d2 66  f7 34 88 54 0a 66 31 d2
|f.D|f1.f.4.T.f1.|
00000110  66 f7 74 04 88 54 0b 89  44 0c 3b 44 08 7d 3c 8a
|f.t..T..D.;D.}<.|
00000120  54 0d c0 e2 06 8a 4c 0a  fe c1 08 d1 8a 6c 0c 5a
|T.....L......l.Z|
00000130  8a 74 0b bb 00 70 8e c3  31 db b8 01 02 cd 13 72
|.t...p..1......r|
00000140  2a 8c c3 8e 06 48 7c 60  1e b9 00 01 8e db 31 f6
|*....H|`......1.|
00000150  31 ff fc f3 a5 1f 61 ff  26 42 7c be 7f 7d e8 40
|1.....a.&B|..}.@|
00000160  00 eb 0e be 84 7d e8 38  00 eb 06 be 8e 7d e8 30
|.....}.8.....}.0|
00000170  00 be 93 7d e8 2a 00 eb  fe 47 52 55 42 20 00 47  |...}.*...GRUB
.G|
00000180  65 6f 6d 00 48 61 72 64  20 44 69 73 6b 00 52 65  |eom.Hard
Disk.Re|
00000190  61 64 00 20 45 72 72 6f  72 00 bb 01 00 b4 0e cd  |ad.
Error.......|
000001a0  10 ac 3c 00 75 f4 c3 00  00 00 00 00 00 00 00 00
|..<.u...........|
000001b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
|................|
000001c0  01 00 ee fe ff ff 01 00  00 00 af ea 42 25 00 00
|............B%..|
000001d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
|................|
*
000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa
|..............U.|
00000200  45 46 49 20 50 41 52 54  00 00 01 00 5c 00 00 00  |EFI
PART....\...|
00000210  48 65 3e f7 00 00 00 00  01 00 00 00 00 00 00 00
|He>.............|
00000220  af ea 42 25 00 00 00 00  22 00 00 00 00 00 00 00
|..B%....".......|
00000230  8e ea 42 25 00 00 00 00  d5 ac 62 b6 5c 05 ee 4b
|..B%......b.\..K|
00000240  98 53 9f d6 16 4d 16 3a  02 00 00 00 00 00 00 00
|.S...M.:........|
00000250  80 00 00 00 80 00 00 00  aa 27 c6 ca 00 00 00 00
|.........'......|
00000260  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
|................|
*

I'll have to test this disk on a few different machines to figure out if
this is a broken HP BIOS or I just got lucky on Asus.

 -Arun
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