CentOS - Dec 2020 - Oracle Linux - oracle-epel vs epel - dnf priority

I'd like to run this by you guys and get your opinion.

For those of us who are considering moving to Oracle Linux (or at least doing
some experimenting with it), I just had an idea for dealing with the fact that
the oracle-el-epel apparently doesn't have all of the packages that are in
the fedora-el-epel that we all know and love.

It makes sense to me to use the oracle epel with OL to the greatest extent
possible simply because it's part of OL.

To get around the missing package issue, what about setting up both oracle-epel
and fedora-epel, and then using the dnf priorities to pick the stuff from
oracle-epel first and if it's not there then grab it from fedora-epel.

One issue that I can see (though it may not be an actual issue) is the way the
priorities setting works:

QUOTE:
priority
    integer
    The priority value of this repository, default is 99. If there is more than
one candidate package for a particular operation, the one from a repo with the
lowest priority value is picked, possibly despite being less convenient
otherwise (e.g. by being a lower version).
END OF QUOTE

By setting fedora-epel to a lower priority, the if a package we want is only in
fedora-epel, we'll grab it from there.  But if that package has a dependency
on another package version X  that can be found in fedora-epel and for some
reason oracle-epel supplies only package version X-1, what happens then?  Is dnf
smart enough to pick the higher-versioned (and required) package from
fedora-epel even though it has a lower priority.

I'll try to explain that again.

I want to install Foo, which is only in fedora-epel.

Foo requires Bar version 2.0.

Bar 2.0 exists in fedora-epel, but oracle-epel has only Bar version 1.0.

What happens then?  Does dnf see that Foo requires Bar-2.0 and get it from
fedora-epel even though it has a lower priority?

-- 
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On Mon, 14 Dec 2020 at 13:41, Frank Cox <theatre at sasktel.net> wrote:
> I'd like to run this by you guys and get your opinion.
>
> For those of us who are considering moving to Oracle Linux (or at least
> doing some experimenting with it), I just had an idea for dealing with the
> fact that the oracle-el-epel apparently doesn't have all of the
packages
> that are in the fedora-el-epel that we all know and love.
>
> It makes sense to me to use the oracle epel with OL to the greatest extent
> possible simply because it's part of OL.
>
> To get around the missing package issue, what about setting up both
> oracle-epel and fedora-epel, and then using the dnf priorities to pick the
> stuff from oracle-epel first and if it's not there then grab it from
> fedora-epel.
>
>
Having done this for years.. choose one or the other. Do NOT mix the two.
You will end up with heartache and sleepless nights trying to figure out
why things are broken. If you are lucky it is something easy like an update
is broken because the missing EPEL package wants a library that the OEL has
an older version of. In other cases it is the same thing but the soname was
good enough to make rpm think it would work.

I say this as a former EPEL package leader.. either use Oracle EPEL and
figure out how to interact with them to get their rebuilds done faster or
do the same with Fedora EPEL. Priorities and similar filtering tools work
well enough if you have focused repositories where small sets may overlap
but you want X to take over from Y. In the case of nearly 1:1 repos, you
will end up with it working 95%-99% of the time and then burning down the
house.




-- 
Stephen J Smoogen.

Le 14/12/2020 ? 19:41, Frank Cox a ?crit :
> For those of us who are considering moving to Oracle Linux (or at least
> doing some experimenting with it), I just had an idea for dealing with the
> fact that the oracle-el-epel apparently doesn't have all of the
packages
> that are in the fedora-el-epel that we all know and love.
The Yum Priorities plugin (package yum-plugin-priorities) would be nice to
have, but unfortunately it seems to have disappeared. I've used this quite
extensively over the last decade. Whenever I have to use a third-party repo
that's a potential threat to the official repos, I'm setting it up with
priority=10 or something just to be on the safe side.

This has always worked like a charm.

Cheers,

Niki

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