Re: Snapshot/Rollback using LVM/EVMS

[Goswin von Brederlow <brederlo@informatik.uni-tuebingen.de>]

"pavel.orehov@gmail.com" <pavel.orehov@gmail.com> writes:

> Hi,
>
> I am using debian linux and i want to make a system snapshot using LVM
> or EVMS.
> Now i am having running system with one partition (/dev/hda1 of 30GB,
> ~7GB used) and i can't modify or delete existing data.
> I want to take the snapshot (one or more) in some point, save it
> locally and rollback if needed.
>
> My question is what better to use LVM or EVMS?

Lvm snapshots only works on lvm logical volumes. So no luck with your
/dev/hda1. Evms on the other hand can work directly with normal
partitions in some ways. Check for details.


Also you can't realy rollback with lvm snapshots. When you do a
snapshot you create a copy (on write) of the volume. If you change the
original volume (and that is still the mounted system) that volume
remains changed while the snapshot gets a copy of the original data.

To rollback you would have to reboot and use the snapshot device as
your device.

Alternatively you can reboot using the snapshot device before any
alterations. A rollback is then just a reboot with the old device.

As of now there is also now "commit" tool to merge the changes stored
in a snapshot back into the original device. Rollback and commiting a
snapshot is toaly possible with lvm (with an umounted FS on the devcie
you overwrite), there just isn't a frontend for it.

> What exact steps to make system snapshot and rollback with both of
> them?
>
> Note: I have the User Guide of both of them, but it a little confusing.
>
> Thanks,
> Pavel

MfG
        Goswin