emergency boot disk

[der.hans]

Am 28. May, 2002 schwätzte Ronald Jacobowitz so:

> This question concerns creating an emergency boot disk for Caldera Open
> Linux 1.3, which I am using to learn Linux since I have two books of the
>
> "do this, now do that" variety for this distribution.
>
> I would appreciate any reply in language that a newbie can understand.
>
>
> My configuration: 2 HDs, approx 2MB each, with Caldera 1.3 on hdb
>                                            (hda contains Red Hat 6.1)
>                   main OS: Win98, running Partition Magic
>
>
> The Caldera 1.3 installation CD allows the choice of writing LILO either
>
> to the MBR, a floppy, or the beginning of the Linux root partition.
>
> In an earlier installation, I had put LILO on a floppy (which booted
> OK),
> but normally booted using Loadlin from DOS 6.22. This time, since I am
> happily using Partition Magic, I put LILO in the root partition, but
> would
> still like if possible to have an emergency boot disk available.
>
> Several sources suggest that the command
>
>    dd if=/vmlinuz of=/dev/fd0
>
> would do the trick (my file vmlinuz is in /), but when I try to boot
> with
> the disk created by this command, either with or without an extra
>
>    bs=8192
>
> at the end of the command, and either with or without first running
> kfloppy to format the disk
>
>    (Extra Question - when is this necessary?),

You don't need to format the floppy if you're writing to it with dd as dd
wipes the format anyway. Formatting might mark bad sectors such that dd will
skip them, though.

> at the section
>
>    >>> kernel: mounting root filesystem <<<
>
> the following messages appear, some recurring several times and with
> what
> I assume are various memory locations indicated:
>
>    attempt to access beyond end of device
>    unable to read superblock
>    FAT bread failed
>    Kernel panic: VFS: Unable to mount root fs on 03:03
>
> Is there an obvious way to fix this, other than twice reinstalling Linux

What's the size of your vmlinuz? I've got one that's 1.3MB. Another couple
hundred k and it won't fit on the floppy. You should get an error from dd if
the whole thing didn't fit, though. It's been a couple of years since I've
used a floppy. I don't even remember for certain if vmlinuz is compressed,
but I think it is.

Also, if you've still got your install CDs, you should be able to use them
for emergency booting. Same as the bootable business card[1] and other
recovery systems.

ciao,

der.hans

[1] http://www.lnx-bbc.org/
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