re-write is this booting info correct?

[Fbsd1]

Polytropon wrote:
> On Mon, 28 Dec 2009 21:04:57 +0800, Fbsd1 <fbsd1 at a1poweruser.com> wrote:
>> The Microsoft/Windows fdisk program is used to allocate partitions on 
>> the hard drive. This program allocated two types of partitions “primary 
>> dos partition” and “extended dos partition”.
> 
> Just a formal addition: "primary DOS partition" - DOS stands
> for "Disk Operating System", it's an abbreviation. You're
> stating this later on, but you should do it at its first
> occurance.
> 
>

for correctness i agree.

> 
>> A single “primary dos partition” occupying all the space on the hard 
>> drive would be assigned drive letter C.
> 
> The "drive letters" used seem to include the ":" as a part,
> so it would be "C:" instead of plain "C".
> 
>

I have the win98 fdisk english version. I tested this and the fdisk 
program displays just the drive letter with out the :. Now on the DOS 
command line you do have to use the : to change to different drive, like 
in to change to A: drive.

> 
>> An alternate method is to allocate an “extended dos partition” and then 
>> sub-divide it into logical dos drives lettered C, D, E, F.
> 
> I think the term is "logical volume inside an extended DOS
> partition"; I'm not very familiar with their english names,
> but that would correspond to the correct german name (found
> in german versions of DOS); the term is "volume" or "drive".
> 
> I've got no english DOS documentation here, so I can't
> check for the correct term.
> 
> German: "Primäre DOS-Partition" and "Logisches Laufwerk in
> einer erweiterten DOS-Partition", and "Laufwerk" means
> "drive", but I think I recall that DOS uses "volume" for
> this...
> 

The correct word as displayed in the fdisk program is 'logical dos 
drives' just the way i have it.

> 
> 
>> One of these 
>> “primary dos partitions” or one of the logical dos drives in the 
>> “extended dos partition” must be set as the active partition to boot 
>> from.
> 
> I'm not sure you can actually boot from a logical volume
> inside an extended DOS partition... as far as I remember,
> booting can only take place from a primary DOS partition.
> 
> 

I tested this and can confirm you can boot from a logical drive
inside an extended DOS partition. Just have to set the active flag first.

> 
> 
>> FreeBSD’s fdisk program allocates disk space into slices. A FreeBSD 
>> slice is the same thing as a Microsoft/Windows  “primary dos partition”. 
>> FreeBSD has nothing akin to an “extended dos partition”.
> 
> It quite has - its slices (which are subdivided just as the
> extended DOS partitions are, so its partitions are like - 
> but not the same as - the logical volumes inside a DOS
> extended partition).
> 
> 
> 
>> The 
>> Microsoft/Windows partition and the FreeBSD slice is where the operating 
>> system software is installed.
> 
> No. The software is installed on the partitions inside a
> slice, or, to be more exact, in the file system that the
> partition holds. There can be of course one partition
> coviering the whole slice, so "partition(s)" would be
> a valid term.
> 
> 
> 
>> The FreeBSD 
>> ‘disk label’ program is used to sub-divide the slice into smaller chunks 
>> called partitions. In a standard install of FreeBSD, these partitions 
>> are the default directory names used by the operating system.
> 
> Not "are" - they _refer_ to them (or are refered to by
> then), e. g. the default directory name / is the root
> directory, but /dev/ad0s1a is the partition; /usr is the
> directory for { UNIX system resources | user binaries and
> libraries }, but /dev/ad0s1g is (maybe) the partition that
> holds this data. In settings where one partition convers
> the whole slice, there are no further mountpoints for the
> divisions of functional parts of the system.
> 
> 
> 
>> The motherboard standard which was created in the days before windows 
>> desktop were even though of yet and at which time Microsoft DOS (disk 
>> operating system) was the only thing available.
> 
> Sure. :-)
> 
> 
> 
>> This hard drive 512-byte MBR is where all the limitations are. Do to 
>> it’s size the MBR partition table is limited to 4 entries.
> 
> Due to its size...

good catch.

> 
> 
> 
>> This means no 
>> matter how large your hard drive is (20MG or 200GB) you can only 
>> sub-divide it into a maximum 4 slices/partitions.
> 
> 20MB. But I'd like to have a 20 machine gun hard disk, too. :-)
>

back in win3.1 days a 20MG hard drive was the largest made at the time.

> 
> 
>> The default MBR code written by the Microsoft/Windows fdisk program is 
>> hard coded to boot the C drive. The FreeBSD fdisk program has option to 
>> write a simple boot menu program to the MBR.
> 
> You could add that this program is called the "FreeBSD boot
> manager", because that's its actual name.
> 
> 
> 
> Everything else seems to be correct to me, as well as
> written in an appealing way, and technically understandable.
> 
> 


I am adding this verbiage to my FreeBSD installer Guide for
release 8.0 which will be available to the public 1/1/2010 at
http://www.a1poweruser.com/

following is the corrected version incorporating your ideas.

Users with Microsoft/Windows knowledge of how a hard drive is configured 
may have a terminology issue with FreeBSD. Microsoft/Windows and FreeBSD 
use the word partition to mean different (but related) things.

The Microsoft/Windows fdisk program is used to allocate partitions on 
the hard drive. This program allocated two types of partitions “primary 
dos partition” and “extended dos partition”. DOS means “disk operating 
system” which was the precursor to the Microsoft/Windows desktop GUI 
“graphical user interface” first appearing in Win 3.1.
A single “primary dos partition” occupying all the space on the hard 
drive would be assigned drive letter C. You can also sub-divide the hard 
drive into multiple “primary dos partition” each one being assigned a 
drive letter C, D, E, F. An alternate method is to allocate an “extended 
dos partition” and then sub-divide it into logical dos drives lettered 
C, D, E, F. One of these “primary dos partitions” or one of the logical 
dos drives in the “extended dos partition” must be set as the active 
partition to boot from. In a multiple partition allocation only one 
partition can be marked as bootable at one time. Typically legacy 
Microsoft/Windows Win3.1, Win95, Win98, WinMe, and Win2000 defaulted to 
a single “primary dos partition”. Starting with XP, PC manufactures 
started to provide support for their PC’s operating system by having a 
second  “primary dos partition” where the original factory version of 
the system was hidden and used to restore the C drive back to the 
factory version when corrupted by a virus. Microsoft/Windows provides no 
native method of selecting which partition to boot from in a multiple 
partition allocation.

FreeBSD’s fdisk program allocates disk space into slices. A FreeBSD 
slice is the same thing as a Microsoft/Windows “primary dos partition”. 
The FreeBSD ‘disk label’ program is used to sub-divide the slice into 
smaller chunks called partitions. FreeBSD partitions are like (but not 
the same as) the logical drives inside a “extended dos partition”.

The motherboard standard which was created in the days before windows 
desktop were even though of yet and at which time Microsoft DOS (disk 
operating system) was the only thing available. This legacy standard has 
continued un-updated to this current time and contributes to the 
limitations imposed on booting, disk layout and selection of which 
allocation on the hard disk to boot from.

The motherboard BIOS ROM chip at power up inquires each device 
(floppies, cdrom, hard drive, usb memory stick) you selected in the BIOS 
menu to boot from.

The hard drive has a MBR (Master Boot Record) a (512 byte block) located 
in sector-0 of the first physical track on the hard drive. This MBR 
contains bootstrap code and the disk partition table created by the 
fdisk program. The BIOS boot code reads the MBR code and disk partition 
table into memory and then transfers control to it. This MBR code is 
responsible for parsing the partition table and finding the bootable 
slice/partition that is marked 'active'.  The MBR code then sets up the 
disk-address-offset information for the bootable slice/partition, and 
reads 'relative sector zero' from that slice/partition, and transfers 
control to that one-sector block of code that contains the unique 
operating system code to load it into memory.

This hard drive 512-byte MBR is where all the limitations are. Due to 
its size the MBR partition table is limited to 4 entries. This means no 
matter how large your hard drive is (20MG or 200GB) you can only 
sub-divide it into a maximum 4 slices/partitions.

The default MBR code written by the Microsoft/Windows fdisk program is 
hard coded to boot the C drive. The FreeBSD fdisk program has option to 
write a simple boot menu program to the MBR. Its called the "FreeBSD 
boot manager".
There are MBR boot menu programs in the FreeBSD ports collection that 
you can load into the MBR on the first physical cabled hard drive to 
scan for other bootable primary-partitions/slices on this hard drive and 
any other hard drives cabled to the PC. It displays a menu giving you 
the option to choose which one you want to boot from. This gives you the 
ability to have more that one operating system installed on your PC at 
one time.