[Fedora-livecd-list] Re: Review? LiveUSB persistence

[Jeremy Katz]

Moving to the more appropriate list, original is at
https://www.redhat.com/archives/fedora-devel-list/2008-January/msg03188.html for those not on fedora-devel

On Thu, 2008-01-31 at 16:11 -0600, Douglas McClendon wrote:
> I keep hearing these crazy rumors that RedHat actually wants to subject 
> actual users to my LiveUSB persistence feature next/this month.

Lots of people want lots of different things.  I've definitely left this
sitting hanging too long and I apologize.  I just didn't have time to
poke over the holidays and my January was a bitty nutty.  But I should
be back to just my normal mail lag now ;-)

> I for one think the feature is really cool, useful, and know of no 
> showstopping or even known bugs.  But I also would not subject actual 
> users to it, without having had more people review it and sign off on 
> it.  Anyway, to absolve myself of any responsibility, I once again 
> request code review and feedback-

Overall, I think that it looks good.  I think the big thing to work out
is how best to integrate the initscripts changes.  Especially as we're
in parallel switching things over to upstart for F9.  Just to make sure
that I'm clear about what's there so that when we try to bribe Bill, we
can do so effectively...
* The unmount loops in /etc/init.d/functions are modified so that we
don't unmount the underlying fs of the overlay
* We don't want to sync the hwclock on shutdown of a live image
* Do an overlay teardown on halt to replace the rw snapshot with a ro
version

The latter feels like we're going to want a generic hook to be able to
run, perhaps from back in the initramfs.  The middle feels largely
unrelated to persistence in general, but just a "needs fixing" which
will fit in nicely with other hwclock changes that are underway in
rawhide.  And the first I'm less clear on I guess.

Outside of those changes, everything looks pretty straight-forward and
reasonable.  We'll want a little more error checking in
livecd-iso-to-disk and it might also be nice to have another tool that
lets you create your usb stick to use with the actual cd form (I did
this by hand and it was pretty nice that I could easily get it
working!).  As for the findoverlay bits, for right now, leaving them as
a separate script is fine.  In the longer term, we're hopefully going to
kill mayflower and be able to use more "normal" initrds[1], at which
point pulling it in more directly would be nice.

As far as reliability... shutting down cleanly, I can't cause a problem.
I pulled the usb stick from a box and got some garbage in a file I had
written.  I want to do some more playing here, but I also wanted to get
this mail out today.  Worst case, if we say "you need to shut down
cleanly", then so be it.  It might be nice if we flag clean vs not
shutdown so that we can force a fsck in unclean cases.  But no clue if
that's even feasible; I'll take a look, though.

Jeremy

[1] One mkinitrd to rule them all... :)