[Sugar-devel] Unbootable machine

[Jonas Smedegaard]

On Sun, Aug 30, 2009 at 03:21:18PM +0200, Jonas Smedegaard wrote:
>On Sun, Aug 30, 2009 at 07:36:05AM -0400, Luke Faraone wrote:
>>On Sun, Aug 30, 2009 at 07:25, Jonas Smedegaard <dr at jones.dk> wrote:
>>
>>>makebootfat not only formats with disk geometry that *is* right, 
>>>but also use a handcrafted MBR which has a higher chance of 
>>>*looking* right by various BIOSes - both when looking for 
>>>USB-FDD, USB-ZIP and USB-HDD.
>>
>>Now, by *right*, do we mean not only that but also something that 
>>meets the criteria of 
>>http://wiki.laptop.org/go/How_to_Damage_a_FLASH_Storage_Device#How_to_win(without 
>>the problems caused by 
>>http://wiki.laptop.org/go/How_to_Damage_a_FLASH_Storage_Device#Screwed-up_formatting 
>>)?
>>
>>
>>I'm not too familiar with how USB flash works, so I don't know if 
>>USB-{FDD, ZIP, HDD} layouts are compatible with the layout you'd want 
>>to minimize wear.
>
>Please read the following: 
>http://advancemame.sourceforge.net/doc-makebootfat.html#7
>
>If you, after reading above, still feel that your questions are 
>relevant (hint: I don't), then please elaborate on them.

Sorry - I now realize that my response above might be seen as rude.

Thing is, I really didn't talk about how to do things right at all, but 
that in *addition* to do formatting, the makebootfat tool can setup an 
MBR that tricks BIOS into treating the USB stick as a bootable device - 
no matter if the BIOS looks for USB-FDD, USB-ZIP or USB-HDD.

In other words, with makebootfat (if it really holds up to its promise), 
you can create USB sticks that are bootable on more hardware:

Instead of "bootable on hardware that supports USB-FDD boot method" or 
"bootable on hardware that supports USB-ZIP boot method" or "bootable on 
hardware that supports USB-HDD boot method" - makebootfat creates sticks 
that are "bootable on hardware that supports either USB-FDD, USB-ZIP or 
USB-HDD boot methods".

...or, as Peter Anvin points out (if I understand correctly), 
makebootfat creates sticks that are "bootable on hardware that supports 
either USB-FDD, USB-ZIP or USB-HDD boot methods and does note choke on 
the combo tricks in the MBR cheat design".


In other words, makebootfat does not magically deal with the challenges 
of NAND wear - the issue is another: Reliable NAND storage is worthless 
for booting Sugar if your hardware does not recognize the media as 
bootable in the first place!


Hope that helps :-)

  - Jonas

-- 
* Jonas Smedegaard - idealist & Internet-arkitekt
* Tlf.: +45 40843136  Website: http://dr.jones.dk/

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