[Sugar-devel] Documenting the SoaS file system

[Mathieu Bridon (bochecha)]

>>  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.

That's also what I understood. And if I'm not mistaken, the "magic"
involved is a pinch of UnionFS (a read-write partition that is mounted
as an overlay on top of the root filesystem).

Maybe the livecd-tools guys could confirm this. Jeremy, IIRC you
worked on this, could you enlighten us ?


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Mathieu Bridon (bochecha)