[ale] What format is the "make zdisk" Linux boot disk ?

Joe Whitaker dsrekjw at prism.gatech.edu
Fri Nov 7 16:43:02 EST 1997


Thanks for all the responses.
OK, but now I'm curious as to how the floppy boot knows
where my root file system is. There seems to be nothing in
the dd command specifying the root location.
-joew

Jason Boyles wrote:
> 
> On Fri, 31 Oct 1997, Joe Whitaker wrote:
> 
> > When using the command: "make zdisk"
> > The disk boots just fine.
> > What format is it?
> 
>         gzipped ELF with a loading/decompressing boot block prepended.
> 
>         It's just a raw copy of /usr/src/linux/arch/i386/boot/zImage
> written starting at block 0 of the floppy.
> 
> > How can I mount it?
> > I tried to mount it as msdos, ext2,
> > and some others, but no luck.
> 
>         You can't mount it, afaik. Unless you write an fs driver to read a
> zImage from a block device and somehow represent it as a file system. :-)
> 
> > How can I copy it to make a backup?
> 
>         You could dd it from floppy to a file and then dd the file onto
> another floppy, or just dd your extant zImage (usually
> /usr/src/linux/arch/i386/boot/zImage) to /dev/fd0H1440 (or /dev/fd0, if
> you trust the floppy driver format recognition code) like so:
> 
> dd bs=8192 if=/usr/src/linux/arch/i386/boot/zImage of=/dev/fd0H1440
> 
>         This brings up another question for me: normally I dd zImages
> without using the block size parameter. Why does the author of
> /usr/src/linux/arch/i386/boot/Makefile choose to add the bs=8192
> parameter? My bootable kernel floppies work fine, even though I
> rarely use make zdisk, and thus no bs flag.
> 
>         Perhaps it is a convenient multiple of the floppy block size?
> 
> ----
> Jason Boyles <jason at alltel.net>
> "Welcome to The Sanctuary of the Select. If thee come wielding
> the sword of faith to dismember children of sin, thou art welcome."






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