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Re: [Ubuntu-phone] Archive management plans for phone RTM


On Wed, Jun 4, 2014 at 1:20 PM, Colin Watson <cjwatson@xxxxxxxxxx> wrote:
> The current plan is therefore:
>  * Rick has asked me to take ownership of deciding when to branch for
>    RTM; note that this decision can be taken retroactively by copying
>    older versions of packages, so we can say "the image from three days
>    ago looked good but things have been broken since then, so let's
>    branch from that".  I intend to take this decision based on how
>    stable images are and how much tension there is between phone work
>    and development of other parts of Ubuntu;

Another factor that should feed into this decision should be the
schedule/status of our currently ongoing commercial engagements with
our phone OEMs, as they will be another constituency for whom
minimized tension/disruption will be critical around that time frame.

>  * We will then have an "ubuntu-phone" (name TBD) distribution in
>    Launchpad with a series named something like "rtm-14.09", and will
>    land changes for RTM there, allowing other parts of Ubuntu to move on
>    without risk of breaking phone images.  We'll have a -proposed pocket
>    as usual and proposed-migration will operate on it.  I'd like
>    permissions on this distribution to be identical to those in Ubuntu
>    where possible, but we can discuss details there.  There'll be
>    system-image channels for RTM, probably per-device.

The "probably per-device" clause is interesting. Noting it here to
feed into questions below.

>  * We don't want to have to maintain RTM series for a long time.  The
>    plan is to move devices to the next stable branch along as soon as
>    possible.  To facilitate this, the usual rule should be that changes
>    should only go into this distribution after they're already on their
>    way into mainline Ubuntu (as for SRUs), to make sure that we don't
>    end up in a situation where developers land changes on the stable
>    branch but don't quite get round to landing them in mainline.

Agreed that this policy is critical to the long term success of Ubuntu
phone images, as reducing/eliminating rootfs fragmentation is one of
the key differentiators of our platform vs. Android.

> = FAQ =
> Can we use this strategy for other Ubuntu flavours or derivatives?
>   In theory, maybe.  It's very much easier to use this strategy for
>   phone images, though, because the standard distribution mechanism is
>   via system-image channels so we don't need to worry about updating
>   sources.list or arranging for mirroring of the derived archive, etc.
>   There's also a potentially serious social cost to having lots of
>   archive branches, and I wouldn't want to do so except for short
>   durations under tight management; I don't want to see the
>   Ubuntu-and-flavours development community fracturing unnecessarily.

Will this mechanism be able to support an arbitrary number of
commercial downstream flavors? My assumption here is that a commercial
downstream will branch off RTM itself, forming RTM'.

I assume the "probably per-device" channel mechanism could be used here?

A simplifying assumption is that the commercial downstreams will
definitely want to follow the policy of "mainline first" and "have
devices-in-the-field update from next stable branch ASAP", although be
aware that the value of "P" may be on the order of "multiple months".

Will there be some mechanism to recreate the archive at the RTM or
RTM' branch point? I am thinking of a factory hotfix nightmare where
access to the exact source / package versions will be critical in
debugging the issue. We can make the nightmare worse by imagining that
it inexplicably occurs 6 months after initial shipment.


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