Rollback functionality for apt-rpm

[Panu Matilainen]

On Thu, 30 Nov 2006, Panu Matilainen wrote:
>
> I should have time to have a closer look and take it for a test ride this
> evening, I'll comment more thoroughly then.

Took a bit longer than I hoped, sorry. Some additional comments / food for 
thought:

- You certainly do NOT want to store rollback database in /var/cache/apt, 
that data is supposed to be just a cache that can be recreated at any time 
from information available elsewhere. 'rm -f /var/cache/apt/*.bin' is 
a common method for cleaning up the package cache if it has gotten screwed 
somehow. The package data can be restored from package indexes, the 
rollback history not. So I'd suggest moving it to /var/lib/apt (or rather, 
Dir::State) instead.

- For somebody who's concerned enough about the system state to bother 
with rollbacks, storing just the config files might not be sufficient. The 
package in question might have gone offline for whatever reason, and the 
non-config contents might have changed as well (be it a config file not 
marked as such or whatever). Storing the full package contents should be 
possible at least optionally I think. Which brings me to the next point...

- Rpm has native rollback capabilities since 4.0 or thereabouts. Did you 
experiment with using that instead of doing it all yourself? apt-rpm 
honors rpm configuration for creating rollback rpm's (in rpm terms called 
"repackaging") on transactions, what has been missing is a way to do the 
actual rollback via apt. I haven't actually looked into the details at all 
but it might be good/cool/nice to be able to use the native rollback 
capability where it exists and is usable (eg I don't know of rpm 4.0 
rollback quality :). OTOH Debian apt and (apt-rpm on rpm-3.x) could use 
the in-apt rollback support because nothing like that exists in dpkg.

 	- Panu -