(For those looking for an rpm rant, sorry, this isn’t it….!)
Currently there’s a ticket in front of FESCo asking whether or not alternative dependency solvers should be allowed in Fedora’s default install. For those who don’t know, the dependency solver is the algorithm which picks the set of packages to install/remove when a user requests something. So, for example, if the user asks for Firefox to be installed, the “depsolver” is the thing which figures out which other packages Firefox needs in order to work. On occasion, there is more than one possible solution – an obvious example often being language packs; applications usually need at least one language installed, but they don’t care which.
I don’t particularly have much skin in this particular game; but what I would note is that I find it particularly bizarre that this task is delegated to an algorithm. What we’re saying, basically, is that the configuration of a given installation is chosen by a bit of software. So long as the various package requirements – which could be library versions, files, or something entirely synthetic – are all met, the configuration is “valid”. Of course, that doesn’t necessarily mean it works – it may be totally untested by anyone else, and things get particularly grizzly if you’re doing something “fun”. Such fun includes:
- deploying “multi-arch” packages. Maybe you want a 32-bit browser plugin on your 64-bit PC, for example;
- installing third-party packages. Maybe it’s RPM Fusion, maybe it’s an ISV – but where-ever it’s from, it’s another set of variables the depsolvers looks at;
- installing your own packages. See above.
The package management system doesn’t have a concept of “OS” and “other stuff”. Being able to override such a concept would be a feature; not having it is not a feature however.
Now, fans of package management frequently tout the many benefits, and they are indeed multiple. It makes it easy to install new software and be reasonably sure it works (it may need a lot of configuration, though). Splitting stuff up into a thousand different bits makes security updates more straightforward (at least, in theory – see later). But in general, to conflate all these issues is a bit of a mistake: there are other forms of installation system which provide these benefits as well.
So, what’s wrong with this? We’ve already seen that the choice of depsolver can potentially make or break the system, or at least lead to configurations which were not intended by the packagers, but to some extent that could be solved by tightening the specification/package dependencies, so that the “right choice” is obvious and algorithm-independent. But, there are other issues.
It’s difficult to estimate the number of Fedora users, but the statistics wiki page makes a reasonable effort. And looking at that, we can see that about 28 million installs of almost 34 million (that are connecting for software updates) are currently using unsupported releases of Fedora. That’s over 80% of installs using a release which is no longer supported.
This of course has security implications, because these users are no longer getting security updates. No matter how fancy the package management, these people are all on their own. And unfortunately, the package management tools are not much use here: effectively, unless you use the installer in one of its guises, the procedure is difficult and potentially error prone.
You’re also out of luck with third-party repos: the package manager doesn’t insulate them from each other, so mixing is frowned upon. It may work, it may not. You may be able to upgrade, you may not. It may alter core functionality like your video driver, and you might be able to downgrade if it failed, but let’s hope it didn’t manually fiddle with things.
There’s probably an awful lot more that can be written on this topic, and of course package management right now, for the most part, works pretty well. But I worry that it’s a concept which has pretty much had its day.