Today I needed to create a bootable USB stick that does nothing else but just a reboot of the machine.

Why? The machine is booting up from network, but the problem is what happens when the network is down or doesn’t reply fast enough. Unfortunately, the PXE didn’t have the option of booting in an endless loop.

The solution is to:

1. try boot from the network first
2. fall back to booting from USB/CF and reboot the machine

Now, a quick howto on how to create a system like that:

Plug in your USB stick or CF card to the machine. I’m assuming it is found under /dev/hda in your system.

Then:

• With fdisk, create a FAT32 partition, make it active (bootable) and write changes. It should look like this afterwards:

• Then create a dos FS on the partition with

• Install a master boot record (MBR)

• and install a minimal syslinux system. This can be done using the script that can be found here (originally from here) with a command:

where the offset is the number from ” 32 sectors/track” of the fdisk output.

• last but important step, from a FREEDOS image, extract and copy at least the files command.com and kernel.sys. To do that, simply download a freedos iso image from FREEDOS site, and then mount it somewhere with a command:

and then you can copy the files to the /dev/hda1 (which you also have to mount somewhere (-; )

That’s it! You have now a bootable USB stick/CF Card.

Now, the trick to make it reboot. Create an AUTOEXEC.bat file (ahh those old DOS days…), and inside type:

And that’s all, it should work fine.

Expected problems:

• If the systems hangs on “MBR” state when trying to boot, try to invoke syslinux.pl with custom parameters for cylinders, heads and offset, e.g. for the fdisk output above, the offset would be 32, and heads 64.