[Sugar-devel] Documenting the SoaS file system

[Caroline Meeks]

On Wed, Jul 29, 2009 at 9:16 AM, Sebastian Dziallas <sebastian at when.com>wrote:

> Luke Faraone wrote:
>
>> On Wed, Jul 29, 2009 at 08:32, Caroline Meeks
>> <caroline at solutiongrove.com <mailto:caroline at solutiongrove.com>> wrote:
>>
>>    When I read about squashfs in wikipedia or chat with friends about
>>    it, its decribed as read-only and optimized for space.  If we are
>>    rewritting our squashfs everytime the user saves data, that could be
>>    the source of a lot of our failures.  If we never rewrite it, then
>>    probably its a red harring and we need to look elsewhere.
>>
>>
>>  From what I understand, the squashfs is *never* rewritten once created.
>> All changes are stored in a "LVM Snapshot", which is just another file
>> on the underlying FAT filesystem.
>>
>
> As far as I know, what happens is this:
>
> * At build time, all packages are installed (and so is the base system) and
> end up in an image, which gets compressed using squashfs.
>
> * Once you boot your disk / device, any change you make gets saved into
> this spurious file (either for the overlay or home), which contains only the
> changes made since you booted for the first time. Those changes get - again
> afaik - mapped with some magic (don't ask me how, maybe some Fedora folks or
> the wiki know) on the fly into the usual filesystem.


Ahh so its that magic I am looking for the documentation for.

>
>
> --Sebastian
>



-- 
Caroline Meeks
Solution Grove
Caroline at SolutionGrove.com

617-500-3488 - Office
505-213-3268 - Fax
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