Douglas McClendon wrote:
While I haven't by any means given up pursuit of my devicemapper
implementation of persistence, I wonder-
What do people think about using unionfs for persistence (and perhaps
Copy-On-Write in general) in Fedora LiveCDs?
I was somewhat surprised to discover a while back that ubuntu actually
used devicemapper for their COW long ago (early 2005). But that they
abandoned that in favor of the 'flexibility' of unionfs.
I know that unionfs was ruled out as an option for Fedora, because it
was being kept out of the repos. In fact, before pilgrim/livecd-creator
came into existence, I posted a proof of concept fedora unionfs-based
livecd infrastructure-
http://www.redhat.com/archives/fedora-livecd-list/2006-April/msg00197.html
But a lot has changed in the last 18 months. It seems that unionfs is
in the -mm kernel tree, and between that, fuse-unionfs, and aufs, it
seems pretty likely that some flavor of unionfs will make it into fedora
in the foreseeable future.
Given that, and given the multitude of other projects I could be working
on, makes me wonder how much time I should spend working on devicemapper
persistence, if the vast majority of livecds out there are using
unionfs, and unionfs may become an option for fedora in the near future.
Comments?
Never being one to avoid conversing with myself...
It occurs to me that it wouldn't be difficult at all to implement an
initramfs system, that supports *BOTH* devicemapper and unionfs for COW.
With nothing more than a bootarg of cowmethod=<type> to specify
changing from whatever the default method is to the other.
In this fashion, you could actually keep the existing devicemapper
fedora livecd infrastructure, including the nice speedy installer :),
and also support persistence via unionfs on the same livecd.
I still of course think that ubuntu made the wrong decision, and that
devicemapper is ultimately more 'flexible' and better than unionfs. But
I can't deny that unionfs works easily in a lot of ways (spec wrt livecd
persistence), and has certainly enjoyed widespread usage.
-dmc