On Sat, 2014-01-25 at 17:54 -0700, Chris Murphy wrote:
On Jan 25, 2014, at 4:12 PM, Adam Williamson
<awilliam(a)redhat.com> wrote:
>
> * Do an offline update that includes Foo v2.0
> * Boot the updated system, run Foo, it migrates its configuration to
> some new scheme
> * Realize there was something wrong with the update, roll it back
> * Run Foo again, find it doesn't work because it's been migrated to the
> new config scheme which the old version of Foo doesn't work with
I would grumble, but a configuration file being updated and made
incompatible with the prior version would be tolerated. Ideally the
application makes an unmodified copy. If it doesn't, new school
restore with --reflink from snapshot, regular cp if using LVM thinp
snapshots, and old school just restore the file from a conventional
backup. Not such a big deal.
If it's something far less throw away than configuration files being
changed, it's a bit more complicated how badly and quickly the
conversation degrades. But I can hardly recall a recent example of
this happening. It's just not that common in my experience.
What about mail application change the format of the mail folders ?
It happens, and it is *not* data you want to risk throwing away. There
are many other examples like this especially on the server side.
Simo.
--
Simo Sorce * Red Hat, Inc * New York