[Yum-devel] snapshots for rollbacks

Konstantin Ryabitsev icon at fedoraproject.org
Sat Jan 19 20:20:17 UTC 2008

On Jan 19, 2008 1:09 PM, seth vidal <skvidal at fedoraproject.org> wrote:
> > Does the yum plugin live elsewhere? I can only see an apt over debian
> > (over opensolaris) solution there.
> I never received the yum plugin. I was told about it from a user inside
> a very large corporation. The principle of it is fairly simple. Simply
> have the plugin in the pretransaction state perform a lvm snapshot and
> save it.

I may be confused, but I thought LVM snapshots didn't quite work that
way. You can take a snapshot of a partition and mount it separately,
for example in order to acquire a consistent backup. With LVM2 you can
mount snapshots rw, so you can test things out, but it's always done
on a non-live "backup" partition, and any changes will be thrown away.

Theoretically, you can do:

1. Create a rw LVM snapshot of / and mount it on /mnt/snapshot
2. Apply yum updates in the /mnt/snapshot chroot
3. Reboot with the snapshot partition as / to test things out (or
bring up a VM on that root)
4. If all is well, reboot back to live partition, destroy the
snapshot, and apply updates to live
5. If all is not well, then just reboot back to live, and destroy all
attempts at trying

From reading the linked article, I believe they are talking about the
features of ZFS, not LVM. If I'm wrong and completely misunderstand
how LVM snapshots work, then I'll be more than happy to admit it, as
I'd love to be able to do FS rollbacks like that.

Konstantin Ryabitsev
Montréal, Québec

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