Restore UFS snapshot

[pete wright]

On 5/26/07, Svein Halvor Halvorsen <svein.h at lvor.halvorsen.cc> wrote:
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> Roland Smith wrote:
> >> Is it possible to rollback a file system snapshot, i.e. restore the
> >> file system to the state it was in at the time a mksnap_ffs command
> >> was issued?
> >
> > You can mount the snapshot, and then copy the files back to the original fs.
> > Note that cp can preserve flags, but not ACLs AFAIK.
>
>
> Yes, I know that this is possible. However, it's a lot of work.
> There should be some straightforward way of rolling back to a
> snapshot, since the files and all the file system structure are
> already there. Also, there might not be room on the disk for it.
>
>

well, if you are using snapshot's you already have most likely
calculated the overhead that the snapshot(s) will take - so i'm a
little confused at to the lack of room available for the snapshot.
it's not uncommon to have hourly, daily, weekly snapshot's of given
volumes.



> >> User scenario:
> >>
> >> Before a major upgrade (eg. releng->current, portupgrade -a, etc),
> >> it would be nice to mksnap_ffs, and then after the upgrade be able
> >> to either delete the snapshot if all went well, or rollback to the
> >> snapshot.
> >
> > You should use dump(8) in this case. Create level 0 dumps of your
> > filesystems and store them somewhere. You can dump live filesystems with
> > dump's -L flag.
> >
> > If you botch the upgrade, you can use restore(8) to revert your
> > filesystems to the situation before the upgrade.
> >
> > Note that you should really make regular dumps of your filesystems as
> > backups anyway!
>
> This is also beyond the point, although I appreciate that you
> suggest alternative ways to meet my objectives. dump/restore would
> also require additional disk space.
>
> I do actually backup my data on a regular basis, but not all of my
> computers really need external backup, as I could stand some
> downtime. However, if I could easily make a snapshot, and then
> either roll back or delete it afterwards, it would be a nice
> compromise between security and effort. And also: it seems it should
> be possible to do this. If not, I might want to make a tool for it.
>
>

they handbook has a pretty decent example of how to use dump along
side mksnap_ffs - and it seems pretty robust to me.  when dealing with
whole filesystems and important data i think dump(8) is really the way
to go as much work has been put into ensuring that you end up with a
consistent image on disk.

having said that - i see no reason why one couldn't write a wrapper
around dump(8) and mksnap_ffs.

-p

-- 
~~o0OO0o~~
Pete Wright
www.nycbug.org
NYC's *BSD User Group