I have always created an emergency boot floppy during
a Slackware install. However this only creates a boot
disk which boots the install kernel configuration. If I
recompile the kernel, to add drivers, remove unneeded
components to enable hardware to work properly,
I have always created a new emergency disk using
the new kernel and the general command:

dd if=/boot/vmlinuz of=/dev/fd0 bs=8192

I have never had to use one since the new kernel has
always worked properly. However in anticipation of
installing GRUB, I decided to test my disk created in the
above fashion and it failed miserably.

Reading Linux-Boot-HOWTO, I am reminded that an
emergency disk can be created simply by:

make bzdisk

While this is all well and good, I am wondering why the
general copy of the kernel mentioned above doesn't
work. Further reading indicates that to properly create
a disk from a kernel image the following applies:

-------------------------
If you are not using LILO, transfer the kernel to the bootdisk with dd:

% dd if=KERNEL of=/dev/fd0 bs=1k
353+1 records in
353+1 records out

In this example, dd wrote 353 complete records + 1 partial record, so the kernel occupies the first 354 blocks of the diskette. Call this number KERNEL_BLOCKS and remember it for use in the next section.

Finally, set the root device to be the diskette itself, then set the root to be loaded read/write:

rdev /dev/fd0 /dev/fd0
rdev -R /dev/fd0 0

Be careful to use a capital -R in the second rdev command.
-------------------------

Is this essential?

How would I use rdev to change the ramdisk word to indicate
that root should be mounted from the hard disk?

The manpage on rdev is somewhat confusing but it looks
like I would have to use something like:

rdev -R /dev/hda2 0

but it is unclear.

TIA

That is pretty much what I have in my notes for quick and dirty boot disk.
rdev "boot device" "root partition" is the way I use it.
rdev /dev/fd0 /dev/hdax

I ran a 'make bzdisk' on this Slack 9.0 rc1 system and
got the message:

root device is (3, 2)
Boot sector 512 bytes
setup is 4649 bytes
warning: kernel is too big for standalone boot from floppy
dd bs=8192 if=bzImage of=/dev/fd0
122 +1 records in
122 +1 records out

Tried to boot with it and got a repeating message:
AX: 0212
BX: 7600
CX: 0501
DX: 0100
100B

I guess this is the problem. Size of linux in /boot is 1,005,805

Just as a check, I created a boot disk under a Slack 8.0 distro
with a recompiled kernel of size 829,618 and got:

101 +1 records in
101 +1 records out

Booting with this disk works. However, trying to create a disk
with the original install kernal of size 1,396,901 I get:

170 +1 records in
170 +1 records out.

Booting with it produces:

- Uncompressing Linux....
Invalid compressed format (err=1)
-- System halted

Now I know I created a boot disk with this kernal when I
originally installed 8.0 and I know I can go in and create
a new one by running 'setup' again.

What is the maximum size of a kernel that can be fitted to
a floppy?

What does the 'setup' boot disk creation do that a standard
dd'ing does not?

Why can't I run 'setup' in Slack 9.0?

I did create a boot disk in 'setup' when I originally installed
the distro with a kernel size of 1,171,441.

I have not used the 'make bzdisk' command.
I use the 'dd' command you mentioned.
dd if=kernelimage of=/dev/fd0
rdev /dev/fd0 /dev/hdax

Best answer:

Slackware uses SYSLINUX to create a DOS/VFAT type boot
floppy when you create an emergency disk when installing.

The benefit of this is that it puts a copy of your kernel
on a DOS formatted floppy along with some additional
files to make it bootable. The advantage is that the floppy
will now accommodate larger kernel file sizes where the

dd if=/boot/vmlinuz of=/dev/fd0 bs=8192

creates an IMAGE file which can easily overcome the size
limitations of a 144 disk.

My newly created floppy contents are as follows:

03/22/2003 12:07a 1,005,805 vmlinuz
03/04/2003 11:02p 369 syslinux.cfg
03/04/2003 11:03p 7,836 ldlinux.sys
03/04/2003 11:02p 653 f1.txt
03/04/2003 11:02p 678 message.txt

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