Bug#398924: Conflict between Gnome, udev, hotplug and linux-2.4

[Steve Langasek]

On Thu, Nov 16, 2006 at 06:26:22PM +0100, Marco d'Itri wrote:

> > The order is not yet decided, it is just the current way it is written
> > down. If you (or anyone else) could give hints what the best upgrade
> > order is (perhaps even different for different situations), please don't
> > hesitate to tell us.
> When upgrading a 2.4 system, kernel first. It's also the easiest component
> part to rollback.

Kernel first before what?  Before anything else in userspace?

I don't see any reason to worry about rollbacks at all, except in the
specific case of "the new kernel isn't set up right yet, so I need to be
able to reboot to the old kernel to finish the upgrade."  I don't see that
installing a new kernel first helps much with that; whether you install it
first or last, installing linux-image-2.6.18-3-$foo is going to pull in
initramfs-tools -> udev and udev is going to kick out hotplug.  Whether this
happens at the beginning or at the end doesn't seem relevant to the user
experience, since in either case there's a window after hotplug has been
removed and before the kernel has been configured where a power failure
could leave the system in a state that isn't easy to recover from.

On Thu, Nov 16, 2006 at 06:43:07PM +0100, Robert Millan wrote:

> Upgrading kernel first would fix this problem, but I'm not confident to tell
> if that wouldn't bring other -perhaps worse- problems.

Well, I guess one benefit is that if you install the kernel first, the
window between hotplug being removed and the new kernel being configured
*should* be reduced.  If you don't upgrade the kernel first, there's a
possibility that some other package (such as gnome, but there are many
others) will pull udev in and kick hotplug out early in the upgrade, perhaps
even in a completely separate apt run from the kernel upgrade.

> So far I proposed two solutions (letting udev and hotplug coexist, or letting
> gnome-desktop-environment be installed without udev when hotplug is present), I
> think either of these would be better than altering kernel/userland upgrade
> order.

Having udev and hotplug coexist sounds like an interesting possibility.  I'm
surprised to hear that this is even a consideration now; I would encourage
someone to look into this if they have time.

BTW,

> We claim to that we support Linux 2.4 with etch userland, but:

>   - udev doesn't support linux 2.4 (at least not the version shipped with
>     etch).
>   - installing the new gnome-desktop-environment got rid of hotplug.

Please bear in mind that etch's support for Linux 2.4 is intended to be on a
transitional basis *only*; i.e., it's intended that when someone
dist-upgrades from sarge to etch, their packages come up in a working state
*until they have a chance to reboot to the etch kernel*.  It is not intended
that users run etch on a 2.4 kernel indefinitely, so given the complexity of
this upgrade I'm not bothered if there's a point of no return after which
rebooting to 2.4 no longer gives a fully working system -- as long as
booting to 2.6.18 *is* possible...

-- 
Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
vorlon at debian.org                                   http://www.debian.org/