[Fedora-livecd-list] Persistance Overlay

[Jeremy Katz]

On Wed, 2008-06-04 at 19:12 +0100, Pedro Silva wrote:
> So, how does the persistance work:
> 
> - Persistance is created with livecd-iso-to-disk, if I run it again
> without the overlay flag, previous persistance overlay is deleted?

Yes.  Also, the overlay is specific to the *exact* filesystem image that
it is created for.  

... and for the gory details.  The way that persistence is implemented
is that the persistence file is used as the backing store for the device
mapper snapshot that we build on top of the "base" filesystem image.
This means that it contains just changed blocks from the base image and
that changes continue to build up over time, never reusing blocks from
the snapshot.  

So, not ideal for more long-term cases as if you're updating with yum,
then you'll run out of space on your snapshot before you'd expect as we
overwrite things multiple times[1].

Which brings me to what I've been working on this week -- persistence
purely for /home[2].  So rather than using the persistence file for the
snapshot backing store, we instead mount it as /home[3].  At this point,
it's almost to where I'm happy enough with it to push, so stay tuned for
more details :-)

Jeremy

[1] Plus, your kernel will never get updated
[2] Actually, implemented such that you can have persistent changes for
the "OS" as well as a persistent /home.  Then your /home sticks around
when you update the USB stick but any "OS" change disappear as with the
present bits
[3] Including support for encryption