grub-install /dev/fd0 on unmounted floppy disk

vinaytp · 11-18-2009, 06:26 AM

Hi all...

I was studying a study material where its mentioned before installing grub on floppy disk...we have to unmount it...

My doubt is how unmounted file system is detected to install boot loader?

Code:

[root@lyrebird root]# umount /dev/fd0
umount: /dev/fd0: not mounted
[root@lyrebird root]# grub-install /dev/fd0
Installation finished. No error reported.
This is the contents of the device map /boot/grub/device.map.
Check if this is correct or not. If any of the lines is incorrect,
fix it and re-run the script `grub-install'.

Above after unmounting floppy drive..I dont understand how grub-install /dev/fd0 works ?

Can anyone help me please...

Thanks in advance......

DaveQB · 11-18-2009, 06:29 AM

grub-install sets up the device to be bootale with your current boot setup. It has many options that you can use to tell it all sorts. Have a read of the manual

man grub-install

That might shed some more light for you.

vinaytp · 11-18-2009, 06:36 AM

Quote:

Originally Posted by DaveQB

grub-install sets up the device to be bootale with your current boot setup. It has many options that you can use to tell it all sorts. Have a read of the manual

man grub-install

That might shed some more light for you.

Thanks for your reply DaveQB...

But my question is /dev/fd0 should me mounted at some mount point to execute grub-install command right ?

But in the above shown script in a study material they are trying to execute grub-install on unmounted floppy...how is this possible ?

j1alu · 11-18-2009, 06:55 AM

in this how-to:
http://sidux.com/index.php?module=Wikula&tag=GrubFloppy
you also umount the floppy before running the grub-shell.
not that it would answer your question *why* it is so or how it is possible, but it seems to be that way.

as long as it works

DaveQB · 11-18-2009, 06:59 AM

Programs can interact with the block level device, that's how they are mounted and the file system presented to you etc. Like dd can dump a whole drive into a binary file that you can mount, mounting the FS ontop of that to read it.

So grub deals with the superblock of the device, it does not need the file system to be mounted for this. In fact, better not to.

vinaytp · 11-18-2009, 07:35 AM

Code:

grub-install '(fd0)'

Code:

# grub  
 grub> root (fd0)  
grub> setup (fd0)  
grub> quit

Here function of grub-install command
AND
setup (fd0) do same thing ??

malekmustaq · 11-18-2009, 12:15 PM

vinaytp,

Quote:

Here function of grub-install command
AND
setup (fd0) do same thing ??

Yes.
Grub command "setup" is safer to use than "grub-install" and both do the same thing at the boot sector. You did not need to mount the media because you are not reading any data from it: the system is going to perform something to the device, and it better stay as such.

To erase confusion a ten minute reading of this grub tutorial can greatly help you. Just read the topic you needed to know, but bookmark that page to easily return to it as need arises in the future.

Hope it helps.

Good luck.