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Re: custom partitioning



On Sun, 2007-07-29 at 10:26 -0600, Charles Curley wrote:
> On Sun, Jul 29, 2007 at 10:43:50AM -0400, Michael Klinosky wrote:
> > I just got another computer, and I'm stalled in the partitioning 
> > department. I decided to forgo LVM, so I have some questions.
> > 
> > Does it matter in which order I create the partitions? Like, should I 
> > create /boot first?
> 
> Some BIOSes cannot access beyond a given number of cylinders on a hard
> drive. Thus the files to be loaded by the BIOS should be contained
> entirely within the range up to that number. If you create /boot
> first, you will keep those BIOSes happy, and will not cause any
> problems for BIOSes that do not have that restriction.
> 
> > 
> > On the 'Add partition' window is a checkbox: 'Force to be a primary 
> > partition'. What's this? (It's not mentioned in the Installation docs.) 
> > Do any partitions need it?
> 
> This has to do with the history of disk partitioning; it is a kludge
> and a bad hack. Even the terminology is atrocious.
> 
> In short, there are four places in the partition table
> of the master boot record (the first sector of the hard drive). These
> are primary partitions.
> 
> To add more partitions, primary partitions can be relabeled as extended
> partitions, which contain logical partitions. Under Mess-DOS, a given
> extended partition can have no more than four logical partitions. I
> don't know if any other OSs have this restriction. The logical
> partition table for each extended partition is contained in the first
> sector of the extended partition. You do not put file systems on
> extended partitions; they are containers for primary and logical
> partitions.
> 
> Thus to add up to four logical partitions, you must sacrifice a
> primary partition. But you must have a primary partition to keep older
> BIOSes happy (and perhaps current ones; I don't follow BIOS
> development closely these days). So you can have up to 13 partitions
> in a Mess-DOS compliant hard drive.
> 
> In any case, Linux' libata driver cannot recognize more than 15
> primary and logical partitions, so that sets an upper limit.
> 
> So the only partition you should force to be a primary is /boot, which
> should then become /dev/sda1. Let the disk partitioner allocate the
> rest between logical and primary.
> 
> The article at http://en.wikipedia.org/wiki/Primary_partition is
> pretty good, although it confuses things by conflating primary and
> logical partitions.
> 
Great post charles.  I had known some of this but had forgotten about
it.
Regards,
Les H


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