[Fedora-livecd-list] Anyone using the overlay file?

[Jeremy Katz]

On Thursday, January 22 2009, Daire Byrne said:
> ----- "Jeremy Katz" <katzj at redhat.com> wrote:
> > Not usefully -- you can string together some 'dm table' commands and
> > get the number of blocks used but it requires being root and also had
> > some oddities.
> > 
> > My kingdom for an upstreamable unionfs :/
> 
> We use "aufs" to union a COW filesystem for our custom "Live" system. It does seem a little odd that many of the other distros now use a union filesystem approach to LiveCDs and NFS read-only roots but Fedora has for the time being stayed away from it. It's not like there isn't lots of custom stuff being put into fedora/redhat kernels that isn't yet upstream. In fact there was a discussion about getting UnionFS upstream recently on the kernel list....

A discussion that went nowhere fast.  Just like every previous
discussion of unionfs.  And actually, we're _very_ resistent to adding
not-upstreamed stuff into the Fedora kernels.  Things that are in an
appropriate staging tree?  Yeah.  But unionfs isn't even there
 
> Saying all this the dm-snapshot approach will be more efficient space wise as it works with blocks instead of whole files.

But since it works on blocks, you have no way at all to ever reasonably
pull out your changes and apply them for a new image and a lot of other
things

Jeremy