devicemapper and stateless? (was Re: who needs unionfs!, was Re: [Fedora-livecd-list] experimental unionfs and initramfs code)

[Bill Nottingham]

Bill Nottingham (notting at redhat.com) said: 
> > I just saw this go by on planet.fedoraproject.org::
> > http://blogs.gnome.org/view/markmc/2006/04/25/0
> > 
> > notting or jeremy: Is markmc working on something like this as part of
> > stateless or is the devicemapper work he's doing totally unrelated?
> 
> It's related, but it's not part of the readonly-root support. Using
> something like device-mapper for that means you'd have to use a block
> device.
> 
> What LFS appears to be doing is creating a sparse loop device on tmpfs,
> and using that as the block layer. It's a interesting idea, and bears
> investigation.

However, one of the downsides of this approach is it (essentially) makes
the whole root filesystem read-write, which loses some of the benefits
of readonly-root (and makes it a whole lot easier to DoS yourself.)

Bill