[syslinux] centos and extlinux

[Jerry Geis]

I am trying to use extlinux on centos 5.2 i386 to boot a thumbdrive.

I ran the commands:
mkdir -p /boot/extlinux
extlinux /boot/extlinux
cat /usr/lib/syslinux/mbr.bin > /dev/sde
cp /boot/vmlinux.latest.kernel /boot/extlinux/linux

I then tried to boot the USB stick and it started booting
but then it says:

kernel panic unknown root device.

What else do I have to do. I followed the instructions in 
/usr/share/doc/syslinux/extlinux.doc

Thanks,

Jerry