[Sugar-devel] USB stick advice

[Mitch Bradley]

My first order recommendation is "don't use dd to blast an image over 
the existing partition map".

The problem with doing so is that it wrecks the factory partition 
layout.  I strongly suspect that said factory layout is, on many sticks, 
optimized for the characteristics of the stick's internal firmware and 
the hardware block sizes of the NAND Flash chips.

Unfortunately, the alternative is rather more complicated procedurally 
than "dd and pray".  But given the indifferent results from dd&pray, I 
think it may be worthwhile to go for a more elaborate procedure.

Here is an outline of what I think really should be done:

a) Ensure that your filesystem image is somewhat smaller than 1G (or 2G 
or whatever your base size) so it will fit on "all" 1G devices.

b) The image is just the partition contents, excluding the partition 
block and master boot record.

c) The installation procedure involves

c1) Editing (not replacing) the existing partition map, setting the 
first partition's "boot flag" byte and changing its filesystem type to 
ext2 or whatever.  (Ideally it would better not to change the filesystem 
type, instead sticking with the factory FAT partition, but I understand 
what a hard nut that is to swallow for Linux enthusiasts.)

c2) Copying the image into the partition

c3) Installing your bootloader using an installation program instead of 
dd, thus replacing the first sector's Master Boot Record and doing 
whatever else is necessary to complete the bootloader's installation.  I 
have had the best results with syslinux.

There is, of course, a chicken-and-egg problem of how do you run the 
bootloader's installer.  On the other hand, you have the same problem 
with "dd" - in principle, on any machine that can run "dd", you can also 
run syslinux.

If you want to talk more about this issue, please feel free to keep the 
conversation going.  It is a topic that has been much on mind recently.

Mitch



Walter Bender wrote:
> I was wondering if you have any words of wisdom to share with us re
> USB stick compatibility, given your experience with the XO. There
> seems to be a lot of variability in terms of which sticks boot which
> machines in our Sugar-on-a-Stick experiments, e.g., using the same
> machine (a Classmate running XP) to burn the same image (the Beta SoaS
> iso) onto USB storage media from three different vendors, I cannot
> predict which one(s) will be bootable on any particular piece of
> hardware. Is there any deterministic way to proceed, or is trail and
> error our only recourse?
>
> thanks.
>
> -walter
>
>