On Fri, Jul 18, 2008 at 04:23:38AM -0400, x x wrote:
> anyone successfully dual boot with Linux, as well separately dual booting
> with XP/Vista?
Sure.
> I read through the FAQ about Linux and that is 4 years old, and am having
> a major pain and frustration with CHS, same with XP machine, having problems
> around the setting the CHS.
You should not have to set CHS values with a modern (say, less than 15 years
old) BIOS. The drive tells the BIOS what it prefers, and the BIOS should
use that.
> Also in fdisk, in faq for mutibooting only shows 0 is Win-95, 1, 2, and 3
> or unused so e 1, but what if 0, 1, and 2 are each used from a Linux
> distribution, do I e 3, but which do I set as the active partition, do I
> f 0 or f 1 and write to disk for Linux, or do I f 3 and write to disk to
> boot Open?
You need to understand this much about Master Boot Records, and MBR
partitions:
It's a very old design. There is only room in the MBR for 4 partitions.
These are called, "Primary Partitions". An "Extended DOS Partition" is a
method of increasing that number without changing the structure of this old
design; one of the 4 partition slots are used to point to blocks on disk
with additional MBR partitions. This design was invented by Microsoft to
add some logical partitions without impacting any of their PC manufacturing
cusotmers.
Some OS's are very particular about starting and ending addressing and booting.
It is usually best to use each OS's MBR manipulation tools when setting up
multibooting. Windows tools for Windows, Linux tools for Linux, and OpenBSD
tools for OpenBSD.
Today, OpenBSD requires a primary partition. Using OpenBSD's fdisk(8)
program, these are numbered 0-3. If, as you say, on your system 0-2 are used
and 3 is unused, then you must use 3. If all four are already in use, you
must restructure your system to free one of these primary partitions.
The "f" command you mention, "flag", is used to assign the active, bootable
partition for the BIOS.
> When I set CHS to work along side XP on there and reboot nothing works,
> neither OS knows how to load
On boot, the BIOS loads the MBR program from the drive. The partition marked
as bootable ("active" in Microsoft's fdisk program, "flagged" in OpenBSD's)
is determined, and its Partition Boot Record (PBR) is loaded and executed.
If none of the four partitions is marked active, the disk is not bootable.
Below, is the output of "# fdisk wd0" on a laptop with three operating systems:
WXP, Ubuntu, and OpenBSD. There are 4 primary partitions in use, one for
each OS and a fourth, containing the "Extended DOS Partition" which is used
by Ubuntu to create a logical partition for Linux swap.
Note the "active" partition is OpenBSD; though I use the GAG bootloader to
manage multibooting -- it lives in the blocks before partition #0 begins.
Disk: wd0 geometry: 2432/255/63 [39070080 Sectors]
Offset: 0 Signature: 0xAA55
Starting Ending LBA Info:
#: id C H S - C H S [ start: size ]
-------------------------------------------------------------------------------
0: 07 0 1 1 - 522 254 63 [ 63: 8401932 ] HPFS/QNX/AUX
*1: A6 523 0 1 - 1815 254 63 [ 8401995: 20772045 ] OpenBSD
2: 83 1816 0 1 - 2401 254 63 [ 29174040: 9414090 ] Linux files*
3: 05 2402 0 1 - 2431 254 63 [ 38588130: 481950 ] Extended DOS
Offset: 38588130 Signature: 0xAA55
Starting Ending LBA Info:
#: id C H S - C H S [ start: size ]
-------------------------------------------------------------------------------
0: 82 2402 1 1 - 2431 254 63 [ 38588193: 481887 ] Linux swap
1: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
2: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
3: 00 0 0 0 - 0 0 0 [ 0: 0 ] unused
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