[Techtalk] Extended Partitions - I found it! - QUITE! :)

[James]

On 20 Nov 2003 12:18:42 -0500, TechChiq <techchiq at hotpop.com> wrote:

> On Thu, 2003-11-20 at 10:35, Hamster wrote:
>> Well I guess the subject line is a matter of opinion. As far as I'm
>> concerned my question is still unanswered. You've simply stated "use 
>> 0x85"
>> without explaining why.
>
> I tried. You didn't understand what information and links I've given so
> far, so I guess I'll have to let someone else explain it. I think Brenda
> Bell has a good insight on this far better than I so I'll leave this up
> to her. All I know is what I googled and tried to share. I never
> personally tried to use a DOS type partition to run Linux. I used Linux
> for Linux and DOS for DOS. Why would I want to do otherwise? I never
> like to mix apples and oranges unless absolutely necessary.

The different numbers are just a sort of "tag", indicating what filesystem
is inside that partition. Linux uses one particular value for its various
filesystems (ext2, ReiserFS etc), and another for the swap partition -
although in fact it completely ignores the value used. It's still used
for other things: tools such as PartitionMagic care very much what kind
of filesystem they're working on!

Using INT13 or not is irrelevant, by the way, and no version of NT has ever
used INT13 to access disks; even Windows 3.1 has an optional alternative
("32 bit disk access") which improves performance, and is the default on
Windows 95 and later. Linux doesn't - whatever the partition may be -
although apparently someone wrote a driver allowing it to do so if you 
need.

If you don't care about tools like Partition Magic working, you can 
probably
use any partition type you like - Linux won't normally care - although
if you pick the wrong one, booting an OS which recognises that type as 
"mine"
may then trample all over it!

> I don't know if you can even boot up linux from a DOS extended partition
> if Linux is the only OS on your system, because 0x85 tells the computer
> to look for a linux-based filesystem and 0x0F tells the computer to look
> for a DOS-based LBA extended partition. So it may search for the boot
> files differently and thus not find them. If you're not dual-booting,
> there's no reason to put linux on a DOS-type (or Windows-type)
> partition. Why would you want to?

If you just had one large partition (say, a new PC which came with Windows
on) and you don't want to repartition, you could run Linux using the DOS
partition as your root, with a swapfile. Then, you need to have the 
partition
marked as DOS - otherwise, DOS won't recognise it as being its own format.
It'll just ignore anything it regards as a "foreign" format - NTFS, for 
example.


James.