Master Boot Record

[yahooram]

hello everyone

here are lots of posts about grub over-writing when xp installed on linux os.
but i not found any right answer
please tell me-
1. what is master boot record?
2.where it places in computers harddisk?
3.why it over-wright when installing xp on to the linux?
4.is any mechanism here to prevent from over-writing master boot record when installing xp on linux?

please answare these question so than every linux user handle that kind of grub lost.

[Segfault]

1, 2. This is the very first sector on your hard drive. It contains code to boot the operating system(s). Also it has information about primary partitions.
3. MS Windows operating system is designed to be the sole OS in your PC. Thus it assumes nothing important can be on the MBR before Windows install.
4. Use better operating systems than those of Microsoft.

[Rubberman]

You have found out why when creating a dual-boot system you need to install Windows before Linux, BSD, or whatever. It will nuke the boot loader in the MBR so whatever was on the system previously will be unavailable until you restore the GRUB or LILO boot loader you had before.

[yahooram]

hello rubberman
thanks for reply
please define me the answare of my 3 and 4 questions.

[rokytnji]

3.why it over-wright when installing xp on to the linux?

Because Microsoft designed it so. You would have to ask Microsoft why they designed it so.

4.is any mechanism here to prevent from over-writing master boot record when installing xp on linux?

No because when you install windows it does not ask if you wish to install Windows MBR. You do not have a choice Like you do when Linux asks about installing Grub or Lilo and what location you wish to install bootloaders. Windows is not about giving a user choice. Sorry you had to learn the hard way.

Supergrubdisk iso. was made for these kind of problems as well as numerous internet posts on how to reinstall grub when Windows over writes it. Lots of Documentation on this. Super Grub Disk Homepage

[Rubberman]

3.why it over-wright when installing xp on to the linux?
4.is any mechanism here to prevent from over-writing master boot record when installing xp on linux?

Ans. 3: That's what xp does, as Segfault explained. It doesn't recognize any software but itself.
Ans. 4: There is no way to prevent this behavior of XP. As I said before, this is why when you want to create a dual-boot system you first install Windows, and then you install the other operating system(s) such as Linux, BSD, or Solaris.

These days, when I need to run Windows I mostly run it on a virtual machine on a Linux host. If for some reason I need to run Windows directly on the computer hardware, then I have a Windows-only disc for my laptop so I can unplug the Linux disc and insert the Windows disc without bothering anything else. I don't bother with dual booting at all.

[egan]

I'm not sure, but I think you could backup the MBR and restore it if needed as follows:

dd ifdd if=/dev/sda of=/dev/sdb/sda-mbr.bin bs=512 count=1

Assuming you want to back it up to the second partition...

Restore with:
dd if=/dev/sdb/sda-mbr.bin of=/dev/sda bs=1 count=64 skip=446 seek=446

[yahooram]

thanks for replying to all linux gurus

i want to say to rokytnji that i also used super grub disks but
it donse not work for me.

an error message is appears

"/boot/grub/stage1 file is not read correctly."

i follow some steps

boot from linux cd
type these commands
linux rescue
chroot /mnt/sysimage
grub-install /dev/hda

but same error message is appear
"the file /boot/grub/stage1 not read correctly."

that's why i asked these questions.

if any linux guru able to solve this problem please help me.

i am requesting for all gurus.

[rokytnji]

Boot up your live cd and type in (if using Ubuntu because we don't know what distro you are using)
and type in

fdisk -l

and hit enter and copy and paste readout in next post so members can look at your partitions.

[vickey_20]

1. what is master boot record?

Master Boot Record (512 bytes ) is a location on the HDD which contains information ( Like Boot Sector, Partition Table and magic bit) which helps in loading the boot loader like grub or lilo.

2.where it places in computers harddisk?

The MBR is present on cylinder 0 head 0 sector 1 in the first 512 bytes.

3.why it over-wright when installing xp on to the linux?

Thats the way xp is designed to be!!

4.is any mechanism here to prevent from over-writing master boot record when installing xp on linux?

If we make the MBR read only then it wouldn't be possible to over write it. Although I m not sure how to do it but I think it can be done.