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 Boot windows from logic partitions with Grub4dos
post Jun 12 2010, 12:43 AM
Post #1
xpt
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  Joined: 6-March 08
Posts: 48
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Canada


Continue on the topic from

Boot windows from logic partitions
http://www.boot-land.net/forums/index.php?showtopic=11054

because the discussion is now specifically focused on Grub4dos...

QUOTE (Wonko the Sane @ May 31 2010, 10:41 AM) *
. . . To correct the "sectors before" . . .
[*]Using the map --in-situ command, create a TEMPORARY fix:
CODE
map --in-situ (hd0,5)+1 (hd0)
root (hd0,5)
chainloader /ntldr
boot

this will correct the "sectors before" in the partition bootsector automatically and TEMPORARILY. this latter method is extremely convenient as it doesn't "touch" anything, and you can boot from a logical volume "on-the-fly".


Of the 2 given solutions, this is the first method that I tried (because I don't have a free primary partition in the actual machine that I want to use), but somehow it always failed, saying that a certain file can not be found during WinXp boots. The error doesn't make sense to me because I am sure that the ghost image was restored successfully. This started my long journey looking for the answer myself... Long story short, I think I might've found the reason.

Starting from --in-situ. From README_GRUB4DOS.txt that comes with grub4dos-0.4.4:

QUOTE
--in-situ is used with hard drive images or hardrive partitions. With an
in-situ map, we can typically use a logical partition as a primary partition.

In-situ map is a whole drive map. It only virtualize the partition table and
the number of hidden sectors in the BPB of the DOS Boot Record.

While disk emulation may encounter various problems with win9x, the in-situ map
works fine with win9x.


Yes, -in-situ will allow us to use a logical partition as a primary partition. No problem.

Now, the actual problem comes from "(hd0,5)+1". The README already hinted "In-situ map is a whole drive map", but wasn't clear enough.

The best place I found the explanation for "(hd0,5)+1" is at,

http://bbs.znpc.net/viewthread.php?tid=229...page=1#pid32617

This is its machine translation

Look for

QUOTE
In the map command, (hd0, 0) +1 is the (hd0, 0) partition, not (hd0, 0) in the first sector. This indicated that the order applies only in the map, in other places, (hd0, 0) +1, or the original meaning.


which is translated from

QUOTE
在map命令中,(hd0,0)+1是指整个(hd0,0)分区,而不是(hd0,0)的第一个扇区。这种表示只是在map命令中适用,在其它的地方,(hd0,0)+1还是原来的意义。


The actual precise translation is:

In the map command, (hd0, 0) +1 means the whole (hd0, 0) partition, not just its first sector. This meaning only applies in the map command. In other places, (hd0, 0) +1, has the normal meaning.

And the sentence before it, "该菜单是把整个分区的内容装载到内存,要确定内存足够大,否则命令不会成功。" means,

The menu is to load the entire contents of the partition into memory, the memory has to be large enough to hold it. Otherwise, the command will not succeed.

Hmmm... wait a minute, I thought that would explain why some file is not found during WinXp boots, because I definitely don't have enough memory to hold the entire partition. But on looking at the menu entry again,

CODE
title Load Partition From Disk
map --mem (hd0,0)+1 (hd0)
map (hd0) (hd1)   map --hook
root (hd0,0) chainloader +1 boot


I'm not sure now.

Will do more testing and post back.
Again, thanks a lot for your replies, karyonix & Wonko.

Meanwhile, can anyone clarify on this pleases?
Thanks


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post Jun 12 2010, 03:35 AM
Post #2
tinybit
Frequent Member   ***
Group: Developer

  Joined: 14-August 07
Posts: 462
Thank(s): 63


China


Have you tried this?
CODE
map --in-situ (hd0,5)+1 (hd0)
map --hook
root (hd0,0)
chainloader /ntldr
boot


map --in-situ will create an entry in the partition table for the logical partition. The entry will be (hd0,0) if I recall it correctly.

map --in-situ (hd0,5)+1 (hd0) will map (hd0) to itself with virtual partition table for the whole drive (hd0), and virtual BPB for the new virtual primary partition. This is a whole drive map. The int13 routine only virtualize two boot-record sectors(the MBR sector and the BPB sector). All other sectors are not virtual, which means, they are identically mapped to real sectors.

QUOTE
because I don't have a free primary partition in the actual machine that I want to use


You should free an entry for --in-situ to work on.

Just after "map --hook", you may "cat --hex (hd0)+1" and check what have changed in the partition table.
1 user(s) said "Thank you!" to tinybit for this fantastic post:
xpt
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post Jun 12 2010, 01:58 PM
Post #3
xpt
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  Joined: 6-March 08
Posts: 48
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Canada


Thanks a thousand tinybit for your reply. I read from bbs.znpc.net that you are not replying to any email or forum inquiries normally due to your current situation. So your reply is really appreciated.

> You should free an entry for --in-situ to work on.

Just for the archive, if one doesn't have empty entry in partition table, there is still solution,
follow the original thread at
http://www.boot-land.net/forums/index.php?...11054&st=30
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Posts in this topic
- xpt   Boot windows from logic partitions with Grub4dos   Jun 12 2010, 12:43 AM
- - tinybit   Have you tried this? CODEmap --in-situ (hd0,5...   Jun 12 2010, 03:35 AM
- - xpt   Thanks a thousand tinybit for your reply. I read f...   Jun 12 2010, 01:58 PM


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