[wellylug] Help - Confusing partitions

[Jonathan Harker]

Cliff Pratt wrote:
> Carl Turney wrote:
>> (1) Is it important that there is no hda3 partition?
>>
> A disk can normally have up to 4 primary partitions or 1 to 3 primary
> partitions and one extended partition with as many logical partitions as
> you like. (I've vague memories of BSD violating this rule, somehow).
> 
> If there is an extended partition the partition are numbered primary one
> to three and extended four, with any logical partitions from 5 up, even
> if (as is the case here) when there are fewer than three primary
> partitions. So, no, it is not important that there is no hda3.

Yes. I've found it helpful to think of the extended partition as a
container for the logical partitions. So,each disk can only have four
"primary" partitions, numbered 1 to 4, one of which may optionally be an
"extended" partition, which is always given the number 4. The extended
partition itself doesn't do anything except act as a container for
further "logical" partitions, which are always numbered 5 upwards. This
was introduced in the early days of DOS on IBM XT/AT, to get over the
(then) hardware limitation of only having four partitions per disk.

>> (2) Should I expect any difficulty in creating an hda4 partition
>> without creating an hda3 first, using fdisk?
>>
> No, the extended partition will be hda4. I think there has to be one
> primary partition at least, though.
>>
>> (3) Is hda5 truly a =logical= LINUX partition, created within a
>> =physical= Windows partition, hda4?  (Note same start & stop
>> cylinders.)
>>
> It's not Windows, it's 'extended'. There is no OS at this level. The
> extended partition contains logical partitions.
>>
>> (4) Could the logical hda5 be created using LINUX's fdisk, as I
>> seriously doubt that any genuine Micro$oft Windows utility would
>> offer creation of a logical LINUX partition?
>>
> Yes, if you create an extended partition, then a logical partition
> within it, the first one will be hda5. This is true of Windows fdisk
> too, except that the partition type won't be Linux.
>>
>> (5) Would Ubuntu be able to "seamlessly" work, if I bypassed the
>> Windows hda4 partition altogether?
>>
> It's nothing to do with Windows. Yes, you can create the disk with no
> extended partition, and just root, swap and home all as primary partitions.
>>
>> (6) What possible benefits are there to such a "logical within a
>> physical" setup, in the original (working) hard disk?
>>
> If you want more than four partitions, you have to use an extended
> partition, eg:
> 
> /dev/hda1    primary
> /dev/hda2    primary
> /dev/hda3    primary
> /dev/hda4    extended, contains the following
> /dev/hda5
> /dev/hda6
> ....
> 
> The fact that /dev/hda2 and /dev/hda3 may be missing confuses those new
> to disk partitioning. In your setup there is no advantage in the
> extended partition.
> 
> Cheers,
> 
> Cliff
> 
>