Public SourceMage Discussion List

[Juuso Alasuutari <iuso AT sourcemage.org>]

I've been thinking more about how to make the transition from hotplug to udev 
work smoothly for stable 0.4 -> 0.6. My conception is that there are two main 
obstacles:

1) Udev needs to replace hotplug during system-upgrade if both are already 
installed, but hotplug needs to be available for e.g. static /dev systems.
2) The new udev needs to be cast after linux if both are in the install queue.


Possible solution for 1:

This would be easily solved if we could just deprecate hotplug in favor of 
udev. But there are those who use static /dev or want to experiment. 
Therefore I suggest this solution:

- Add 'conflicts hotplug y' in udev, so that it will overthrow hotplug when 
cast. (Having udev installed implies that you're not a static /dev user.)
- Add a check in hotplug that will abort cast if udev > 0.91 is installed and 
tell the user why. This will fix situations where both udev and hotplug are 
in the queue and hotplug is cast after udev -- without this check udev would 
dispel hotplug, but it would then be cast again.

One problem I can see with this is, that if udev fails to cast, the user will 
be left without a new udev and hotplug. But I think we can't absolutely 
guarantee that a conflict is safe, or can we?


Possible solution for 2:

This problem stems from the fact that the new udev spell won't cast if linux 
< 
2.6.15. If during a system-upgrade udev is queued before linux, linux will 
still be 2.6.14.2 when udev attempts to cast.

It would be a neat solution to add 'depends linux' in udev, but we won't do 
that because some users prefer custom kernels. For them we can't guarantee 
that the system-upgrade pulls through unless they cast a new kernel before 
it, but that's the risk that one takes with custom stuff. We should mainly 
worry about udev working together with the linux spell without enforcing 
linux on anyone.

Something that a few people have suggested already is adding an up_trigger in 
linux. It would trigger a udev cast if:

- Udev is installed and its version is < 0.92, and the udev in the grimoire 
is 
> 0.91.
- Installed kernel version is < 2.6.15 and the version to be installed is >= 
2.6.15.

These checks should narrow the up_trigger cases to the one time we need to 
worry about, which is the transition.


As always I'm in need of feedback to point out the possible holes in this 
scheme before I implement it.

-- 
        Juuso Alasuutari
[[ Source Mage GNU/Linux ]]

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