A Dos primary partition for all boot loaders?

[saikee]

Edited 11/5/10 - Warning ! - The proposed primary Dos primary partition here is suitable mainly for new installation. It will not suit existing single MS installation due the the rigidity of drive letter created when the MS Windows was first installed. Please see Post #2 for further explanation.

The single Dos partition is alright for new installations if one is prepared to retored Grub everytime a MS system overwriting the MBR. Also MS systems are backward compatible so install from old to new to minimise the work. For example Win2k's NTLDR cannot boot Xp so Xp must be installed after Win2k to avoid repair with the Recovery Console.



A member of Justlinux once write in his signature that "a MS Windows may die one day but not Dos". This is quite accurate as I have found out.

I have found many advantages of putting a Dos in the first partition sda1 in my boot disk. Inside it I have NTLDR, which boots only the Win2k and XP, bootmgr which boots the Vista and Win7 (but able to pass control to NTLDR too) and Grub which can boot all operating systems. Here is the content of my sda1

linux-8w65:/mnt/sdb21 # ls /mnt/sda1
1st_bcd       boot         BOOTSECT.BAK        DRVSPACE.BIN  pagefile.sys  SUHDLOG.DAT
1st_bcd.LOG   BOOT.---     BOOTSECT.DOS        IO.SYS        ProgramData   SYSTEM.1ST
1st_bcd.LOG1  Boot.BAK     COMMAND.COM         MSDOS.---     $RECYCLE.BIN  System Volume Information
1st_bcd.LOG2  boot.ini     CONFIG.DOS          MSDOS.SYS     Recycled      WINDOWS
arcldr.exe    BOOTLOG.PRV  CONFIG.SYS          NETLOG.TXT    RHDSetup.log
arcsetup.exe  BOOTLOG.TXT  d899a95043109a710a  NTDETECT.COM  service.log
AUTOEXEC.BAT  bootmgr      DBLSPACE.BIN        ntldr         SETUPLOG.TXT

I have highlighted the relevant boot loaders in different colors. As you can see they can live happily together. The Grub here is Grub1 or Legacy Grub. Grub2 is less versatile, has many restrictions, needs longer commands and is not preferred here.

Red is for Dos own boot files

Blue is for the NTLDR's essential boot loader files

Purple is the bootmgr boot loader. Its BCD data is inside the /boot dirctory.

Magenta is where Grub is housed

The /boot (showed up as \boot in Dos) directory has both the bootmgr other files as well as the grub directory which has the 3 essential Grub1 files highlighted in magenta here.

linux-8w65:/mnt/sdb21 # ls /mnt/sda1/boot/grub
bash1  menu.lst  menu.lst.backup  stage1  stage2

Advantages

(1) All the NT MS Windows systems can be placed in the logical partitions because they all need just their boot loaders in a primary partition marked "active" (or bootable in Linux term). In my case I have Win7 in sda6, Win2k in sda7, Vista-64 in sda8 and Xp in sda9. XP and Win2k can only be booted by NTLDR whereas Vista and Win7 are booted by bootmgr. Basically bootmgr takes over the bootsector and provide an alternative to switch to NTLDR within its booting menu. Naturally both bootmgr and NTLDR can fire up Dos in the sda1 too.

(2) Grub can be conveniently house in sda1 as it can read a Dos partition with filing system in FAT32 (Type c). It only needs two files, stage1 and stage2, inside and optionally the 3rd file menu.lst. Without the menu.lst Grub boots to a Grub prompt. Any installed system can be fired up manually in a Grub prompt so it is a pretty powerful set up.

(3) One can write a Grub boot menu before any other operating system is installed. That has to be the coolest thing to do and you know what you can generate such menu by a Bash script just like this

for ((i=1;i<=60;i++));do echo "title @ sda$i";echo "root (hd0,$(($i-1)))"; echo "chainloader +1"; echo " 
";done  > /mnt/sda1/boot/grub/menu.lst

In the above I mounted the sda1 partition on a mounting point /mnt/sda1. The loop shows I intend to boot 60 partitions.

I have only assembled the 4 MS system (all booted from sda1) and one Linux in sda19 and my menu.lst, after a few editings, currently stands as

title W2k/Xp, Vista/Win7 and MS Dos @ sda1
root (hd0,0)
chainloader +1
 
title @ sda2
root (hd0,1)
chainloader +1
 
title @ sda3
root (hd0,2)
chainloader +1
 
# sda4 is an extended partition and not bootable
 
# sda5 is the common swap used by all Linux
chainloader +1
 
title @ sda6
root (hd0,5)
chainloader +1
 
title @ sda7
root (hd0,6)
chainloader +1
 
title @ sda8
root (hd0,7)
chainloader +1
 
title @ sda9
root (hd0,8)
chainloader +1
 
title @ sda10
root (hd0,9)
chainloader +1
 
title @ sda11
root (hd0,10)
chainloader +1
 
title @ sda12
root (hd0,11)
chainloader +1
 
title @ sda13
root (hd0,12)
chainloader +1
 
title @ sda14
root (hd0,13)
chainloader +1
 
title @ sda15
root (hd0,14)
chainloader +1
 
title @ sda16
root (hd0,15)
chainloader +1
 
title @ sda17
root (hd0,16)
chainloader +1
 
title @ sda18
root (hd0,17)
chainloader +1
 
title OpenSuse 11.3 @ sda19
root (hd0,18)
chainloader +1
 
title @ sda20
root (hd0,19)
chainloader +1
 
title @ sda21
root (hd0,20)
chainloader +1
 
title @ sda22
root (hd0,21)
chainloader +1
 
title @ sda23
root (hd0,22)
chainloader +1
 
title @ sda24
root (hd0,23)
chainloader +1
 
title @ sda25
root (hd0,24)
chainloader +1
 
title @ sda26
root (hd0,25)
chainloader +1
 
title @ sda27
root (hd0,26)
chainloader +1
 
title @ sda28
root (hd0,27)
chainloader +1
 
title @ sda29
root (hd0,28)
chainloader +1
 
title @ sda30
root (hd0,29)
chainloader +1
 
title @ sda31
root (hd0,30)
chainloader +1
 
title @ sda32
root (hd0,31)
chainloader +1
 
title @ sda33
root (hd0,32)
chainloader +1
 
title @ sda34
root (hd0,33)
chainloader +1
 
title @ sda35
root (hd0,34)
chainloader +1
 
title @ sda36
root (hd0,35)
chainloader +1
 
title @ sda37
root (hd0,36)
chainloader +1
 
title @ sda38
root (hd0,37)
chainloader +1
 
title @ sda39
root (hd0,38)
chainloader +1
 
title @ sda40
root (hd0,39)
chainloader +1
 
title @ sda41
root (hd0,40)
chainloader +1
 
title @ sda42
root (hd0,41)
chainloader +1
 
title @ sda43
root (hd0,42)
chainloader +1
 
title @ sda44
root (hd0,43)
chainloader +1
 
title @ sda45
root (hd0,44)
chainloader +1
 
title @ sda46
root (hd0,45)
chainloader +1
 
title @ sda47
root (hd0,46)
chainloader +1
 
title @ sda48
root (hd0,47)
chainloader +1
 
title @ sda49
root (hd0,48)
chainloader +1
 
title @ sda50
root (hd0,49)
chainloader +1
 
title @ sda51
root (hd0,50)
chainloader +1
 
title @ sda52
root (hd0,51)
chainloader +1
 
title @ sda53
root (hd0,52)
chainloader +1
 
title @ sda54
root (hd0,53)
chainloader +1
 
title @ sda55
root (hd0,54)
chainloader +1
 
title @ sda56
root (hd0,55)
chainloader +1
 
title @ sda57
root (hd0,56)
chainloader +1
 
title @ sda58
root (hd0,57)
chainloader +1
 
title @ sda59
root (hd0,58)
chainloader +1
 
title @ sda60
root (hd0,59)
chainloader +1

You will find I have arranged every partition to be chainloaded. Grub can chainload any operating system as long as there is a boot loader residing in the boot sector.

Every MS system, from Dos to Win7, ever invented by M$ always has a boot loader inside its boot sector. Therefore they are always chainloadable. This is true for all BSD and Solaris systems that have to be installed in a primary partition.

For Linux the system will be chainloadable if the boot loader, be it a Grub1, Grub2 or Lilo, is placed in the root partition where the Linux is installed.

Therefore whenever I install a Linux all I need to do is to tell its installer that I want my boot loader to be inside the Linux partition and it will be fired up by my pre-fixed menu.lst like a clockwork.

(3) The MS boot loaders NTLDR and bootmgr can be nuked and rebuilt without affecting their masters (Dos, Win2k, Xp, Vista and Win7). I have rebuilt these boot loaders manually just to ensure we can do it.

(4) Dos partitions in Fat32 can be accessed by most of the operating systems invented for PC.

(5) There is no better way to learn the MS boot loaders than starting with Dos which every MS Windows must support.

(6) The Dos operating system can actually be omitted in the Dos partition if needed. This is to say the partition sda1 can be data only and has no operating system inside!

(7) Grub does not need to occupy the boot sector of sda1, leaving the bootmgr fully functional to proceed to booting all MS systems.

How to set it up?

(1) Just make a partition sda1 of your chosen size and specify it to have Type "C". This can be done by either command

cfdisk /dev/sda

or

fdisk /dev/sda

make sure to mark it "bootable".

(2) Format it by command

mkfs.msdos -F32 /dev/sda1

This partition is ready for use but cannot boot itself. To make it bootable you need to run a Dos system, either from a CD or a floppy. The command to transfer a MS Dos across is just

sys c:

This should transfer a booting code into the boot sector of sda1 and deposit three files "Command.com", "io.sys" and "MSDOS.sys"

(3) Place Grub inside
To do this you need to boot up a Linux Live CD. Find out where the two essential files "stage1" and "stage2" by asking the kernel with the command

find / -name stage1

Once locate the directory containing stage1 (stage2 will be in the same location) change directory to it, make a mounting point for sda1, mount the sda1 partition, make the /boot /grub dircetory and copy the two files across

mkdir /mnt/sda1
mount /dev/sda1 /mnt/sda1
mkdir /mnt/sda1/boot
mkdir /mnt/sda1/boot/grub
cp stage* /mnt/sda1/boot/grub

To setup Grub in the MBR is to invoke a Grub shell in a Linux root terminal with commands

grub
root (hd0,0)
setup (hd0)
quit

The above Dos partition in fact has lots of booting technology inside. Apart from able to boot any MS and Linux system it can used to demonstrate the difference of (hd0) and (hd0,0) which many users may not even know the difference. The (hd0) is the MBR and the (hd0,0) is the first partition of the first disk. Since my sda1 contains the MS boot loader bootmgr these command in a Grub prompt (obtainable by pressing the "c" key at a text Grub screen) will fire up the bootmgr residing in the boot sector of sda1

root (hd0,0)
chainloader +1 
boot

whereas

root (hd0)
chainloader +1 
boot

fires up the the menu.lst in the /boot/grub directory of sda1.

The above information tells me that the MBR is occupied by the file "stage1". The command "setup (hd0,0)" I issued earlier modifies stage1 and hard-coded the hard disk address of "stage2". When the Bios reads the MBR it loads stage1 into memory. Grub is then able to load its stage2 which is its brain. With stage2 available Grub can check if a menu.lst is available and load it if there is one. When nothing is found Grub defaults to a Grub prompt and the user still has its full functionality.