[Rpm-maint] RFC: Relocate RPM and DNF databases to /usr

[Chris Murphy]

On Thu, Dec 9, 2021 at 5:01 AM Jaroslav Mracek <jmracek at redhat.com> wrote:
>
> Hello Chris,
>
> On Tue, Dec 7, 2021 at 5:01 AM Chris Murphy <lists at colorremedies.com> wrote:
>>
>> Hi RPM and DNF folks,
>>
>> I have a draft change proposal for review and comment, i.e. it's not yet set to be published to Fedora devel at . It's a bit thin, but I expect to fill in more detail following discussion in this thread.
>>
>> https://fedoraproject.org/wiki/Changes/RelocateRPMDNFToUsr
>
>
> The change is not so simple. It is not only the movement of files from one location to another one. We store more types of data in that location - history database (sqlite), module failsafe data (yamls). In future we will store system state data (toml). Data is not only modified after RPM transactions but also by module and mark commands. What I want to say is that the change will be painful but in the proposal there are limited benefits.

I'm pretty sure I'm generally opposed to the idea of logs being rolled
back (in a snapshot and rollback regime). Logs should always carry
forward. Ideally, indicate relevant things like rollbacks in the log,
because rolling back a log is a form of data loss. The history
database sounds more like a log than not. So I'm getting squeamish
about locating that somewhere else. Whereas system state information,
if it's primarily describing /usr, sounds like it needs to get
somewhere in /usr.

Similar to openSUSE, design efforts around a default snapshot and
rollback regime in Fedora are complicated when anything in /var
depends on the state of /usr, and vice versa. As independent and
interchangeable as they can be, I think the better.

> There is also a question in which location DNF can move data. proposed `/usr/lib/sysimage/dnf` is maybe not the best one.

What are some alternative suggestions?


>> Fedora 36 seems like a good time to do this. What do you think?
>
>
> I don't think it is a good time to perform such a change from a DNF perspective. We have a plan to introduce a major update to Fedora 38, therefore it is a better time frame for such a change.

Is it better, worse, or indifferent if the RPM database location were
changed in Fedora prior to any DNF change?


-- 
Chris Murphy