Bug report

Mikkel L. Ellertson mikkel at infinity-ltd.com
Fri Oct 26 13:30:31 UTC 2007


Tim wrote:
> On Thu, 2007-10-25 at 14:56 -0700, Rick Stevens wrote:
>> Ah, the makeactive thingie may have something to do with it.  That
>> sets the "active" flag in the partition table on the disk so the OS
>> marks that as /dev/sda.
> 
> I don't see why it has to have that effect.  It just means that this
> partition is bootable.
> 
>> There can only be one "active" partition in the system.  DOS and early
>> Windows systems use that flag to know where they were booted from.
>> It shouldn't be necessary for a Linux kernel, grub or lilo. 
> 
> I have a system with three drives, each have an active partition.  It
> works without any problems, including being able to boot Windows from
> one of them.  As far as I was aware, the issue was to help the BIOS
> provide a list of which were the bootable choices, not the OS.
> 
The makeactive is more for OS's that insist that they be booted from
the active partition. It does not affect loading another copy of
Grub, or the booting of Linux. Both Grub and Linux are more then
happy to load off of non-active partitions and drives other then the
first drive. (As long as the BIOS can access them for Grub.) For an
example of this, you can use the XP boot loader, and have loading
Linux using Grub as an option.

Linux will also boot from a non-primary partition, and you can only
make primary partitions active. I have also booted Linux systems
without an active partition. But this depends on the BIOS, because
some BIOS refuse to try and boot anything if they do not find an
active partition, while others will boot if they find a valid boot
loader signature on the MBR, regardless of any active partition.
Then there are the ones that only check for an active partition if
they do not find a boot loader in the MBR, and check for a valid
boot loader signature on the boot record of the active partition. I
have even run into a few that will boot with only extended partitions.

Oh yes, this only applies to systems with a DOS type partition
table. There are other types of partition tables with their own rules...

Mikkel
-- 

  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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