[arch-dev-public] For how long should we support a smooth update?

[Dieter Plaetinck]

On Sat, 11 Dec 2010 18:23:27 +0100
Pierre Schmitz <pierre at archlinux.de> wrote:

> Hi all,
> 
> because our development is always moving forward we sometimes need to
> break compatibility with old installations of Arch. For example
> switching to xz as compression for all packages of course requires a
> version of libarchive which can handle it. Allan's request for bumping
> glibc's kernel dependency is similar (but also a special case). Or
> imagine some special treatment in install files when updating from old
> package versions. We have also had some repository changes which made
> updates from very old setups difficult or broke old install isos.
> 
> I would suggest to decide on a maximum age within which an update
> should be supported. What about one year? That would mean updating a
> system which hasn't been updated for more than one year or installing
> from an ISO image older than one year might not work.
> 
> The benefit of such a defined "rule of thumb" would be that code and
> packages can be simplified and we are not hold back by keeping very
> old backwards compatibility.
> 
> A side effect of this rule would be that keeping your system up to
> date is a requirement for using Arch. This is no big deal though and
> should affect virtually nobody.
> 
> What do you think? Would you agree in general? Is a year too short or
> too long?
> 
> Greetings,
> 
> Pierre
> 

interesting question.
Isn't it already in our guidelines/recommendations somewhere that
Arch users need to update their system regularly (at least weekly or
so), and if they don't like that, Arch is not for them?
I would say we only stretch this support period for the maximum amount
of time needed, not a timeframe we just make up.

As far as I know, the biggest bottleneck are release media.
So I would say: we support upgrade paths from system as old as the
latest official release media, or newer.
In this case, the newest release is 2010.05, so if a users system was
last updated in April, that's too old to still support upgrades.

There is a potential edge case / race condition when new, breaking
features are released shortly after a media release. (or in other
words: users would need to upgrade right away when new official images
are released), maybe we should take oldest release + 1 month, or so.

If we'll ever be at a point where we do frequently official
releases (like each 3 months), we probably don't want to force users
to download the new image if they have one of 3 months old.  We can
capture that in our statement as well by saying something like "we
support upgrades on systems as old as the oldest release media whose
age does not exceed 6 months (unless the latest release media are older
then 6 months, in which case we support from then and onwards)"

Dieter