[Sugar-devel] USB stick advice
wmb at laptop.org
Mon Apr 13 15:53:44 EDT 2009
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
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.
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?
More information about the Sugar-devel