Making a spare boot up floppy

[Jeff Vian]

Barry Yu wrote:

> Jeff Vian wrote:
>
>>
>>
>>>
>> I agree on the utility of booting from CD.  However, the OP had asked 
>> what he did wrong in trying to make the bootable floppy.  :-)
>>
>>
>> It never hurts ot answer the question that was asked.  :-)
>>
>>>>
>>>> On Sun, 2004-03-28 at 18:42, Jeff Vian wrote:
>>>> > The easiest way to make a usable (and bootable) image of a boot 
>>>> floppy
>>>> > is with dd.
>>>> > Use "dd if=/dev/fd0 of=boot.img bs=512 count=2440" to create the 
>>>> file
>>>> > boot.img that is an exact copy of the floppy.
>>>> >
>>>> > That will create a bootable image of the floppy that then can be put
>>>> > back onto another floppy using rawrite from dos/windows, or dd on 
>>>> linux.
>>>>
>>>>
>>>> > Barry Yu wrote:
>>>>
>>>> > >I want copy all contents in the bootable floppy into my data 
>>>> storage partition, and copy them back into a blank floppy in case I 
>>>> need - I had bad experience in open a blend new box of floppy and 3 
>>>> consecutive floppy even not workable at all! I must prepare if the 
>>>> current boot floppy one day is gone. Moreever, I really want to 
>>>> know above copy process what have I missed that caused the new 
>>>> floppy not bootable even with correct contents in it (At least I 
>>>> can't see what I had missed).
>>>> > >Thanks for helping.
>>>>
>>
>>
> Exactly, what I wanted to know is ; Why I can't copy the contents of  
> a bootable floppy? Because after I have copeid I copared both floppies 
> (The original and the new copy) I obviously found nothing wrong but 
> the new floppy just won't work, that is what I want to find out.
>
As I said in my first answer,  making the floppy bootable is NOT the 
same as copying files to it.
The boot sector must be written to make it bootable.  Copying files 
to/from the floppy does not affect the boot sector of the disk, thus it 
does not make it bootable by the simple act of copying the needed files 
to the disk.

Making a floppy with "mkbootdisk" writes the boot sector to make it 
bootable, as does "sys" in dos/windows.  Then my method of creating a 
duplicate of the bootable diskette once made will recreate the boot 
sector exactly as written so the copy is also bootable.
 
Please note, that if a floppy has any bad sectors when formatted it 
CANNOT be used to read/write an exact image since the image will be the 
size of the full disk and bad sectors will mean the image is not 
restored properly.