pre-upgrade backup

[Christopher Browne]

On Wed, May 26, 2010 at 11:36 AM, Matt Price <moptop99-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org> wrote:
> Anyway, since the whole family uses this computer, I'm anxious about a
> failed upgrade, and am wondering if anyone out there uses a version
> control system or something that would let one roll back an upgrade if
> it's severely broken.  For instance, I'm thinking I could put /etc
> under git or something, and use dpkg --get-selections to get a list of
> packages?  And if the things go badly wrong, I could just roll back
> /etc/ and reinstall everything from the karmic repos or something.
> /home is unfortunately not on a separate partition but all our video
> files are, so most of our media should be relatively safe.
>
> anyway, i'd appreciate hearing any thoughts.  thanks!

Disk drives are cheap enough that I'd be strongly inclined to have the
backup be that:

- The old installation remains on the old drive, completely untouched

- The new installation is done on a new drive, and whatever data
appears relevant is copied over

If you want to roll back, you just mount the old drive.  And that
costs you, what, maybe $100.  The amount of time required to try to do
this on a single drive, or to repair things if something goes woefully
wrong, is likely to be worth quite a bit more than $100.

It may be a lovely idea to have a Git repository that captures some
portion of what's in /etc; that's pretty independent of this.  It's a
regrettable thing that /etc tends to capture quite a lot of static
information that, for instance, you'd want an RPM/deb package to
update.

Life would be better if we consistently had:
 /etc - containing only the data that YOU ENTERED
 /var/packaged-stuff/etc - containing data provided by packages and such

But I don't think it would be notably easy to get to that point.  The
nearest would be to establish your own repository...

 /etc - contains all the configuration of all sorts, including cached
copies of DATA YOU ENTERED

 /usr/my-etc - contains original copies of the files that you
customized, which could be managed as a Git repo or some such thing

Then...   Something automated would periodically (polling/event driven
I leave to others) copy anything changed in /usr/my-etc into the
appropriate spot in /etc

I've done things somewhat resembling this using cfengine.
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