multi-OSes and partitioning

Gary W. Swearingen garys at
Mon Apr 10 18:44:41 UTC 2006

taeb <taeb at> writes:

> On Sat, Apr 08, 2006 at 10:15:45PM +0200, Alan McKinnon wrote:
> <SNIP>

> Well, that clears up one fuzzy area for me.  One of the sites I read
> said: ... up to three of the partitions could be marked as EXTENDED ...

I'm fairly sure that all four can be marked as "EXTENDED" (with
non-standard software) but little or no software will handle that
configuration as well as you might wish.  One way to abuse the scheme
is to make and fill an extended partition with some sub-partitions
and then change the partition type to "0" and then make a different
extended partition with subpartitions.  Then you could switch between
the two by swapping partition types between "extended" and "unused".


>> > The partitioning scheme I'm planning to use is:
>> >
>> > P1: freeDOS     ~100MB
>> > P2: minix3      ~900MB
>> > E3: freeBSD     ~59GB
>> > E4: Linux       <remainder of disk>
>> >
>> > Inside E4 would be partitions 5-9 laid out something like:
>> > p5: Linux-1     to hold one version of Ubuntu -- current or next
>> > p6: Linux-2     to hold another version of Ubuntu
>> > p7: swap
>> > p8: Home
>> That won't work, you have two extended partitions and can only have 
>> one (maybe E3 is a typo). This will work better:
> Nope.  I thought you could have more than one extended part.  As a test
> I just tried creating more than one extended part, and by golly it only
> let me do one. :)

I hope you haven't confused FreeBSD's "slice" with an "extended
partition".  They serve the same purpose, both having what I call
"subpartitions" or "secondary partitions".  AFAIK, "logical
partitions" is sometime used synonomously, but is a kind of
bastardation of IBM's term "logical drive" which could be either
primary or secondary.

>> P1: freeDOS	~100M
>> P2: minix3	~900M
>> P3: freeBSD	~59G
>> E4:		remainder
>>   L5: Linux 1
>>   L6: Linux 2
>>   L7: swap
>>   L8: home
> If I understand correctly it sounds like I could skip P3, put a
> partition inside E4 and let freeBSD use it.  Not sure that'll work,
> although I might try it if I have some time, just to see.  I'll probably
> stay with something like the above. :)

IIRC, a guy who should know told me that you can put a BSD slice with
BSD partitions (I'll call subpartitions) within an extended primary
partition like that, but much software will get confused.  FreeBSD
certainly CAN use the E4 subpartitions as if they were a normal
primary partition with no subpartitions; they would be addressed
something like ad0s5, ad0s6, etc.

>> Remember that Linux couldn't care less about this weird partition 
>> convention. The only software where it matters is fdisk and others in 
>> the same class.

I wonder if the boot code which names partitions could get
confused and not give you all the devices you expect.  It DOES
manage to detect my BSD subpartitions from multiple primaries.
(I see an hda15 in dmesg.)

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