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Re: Status and open questions for debian-installer with backports support

On Thu, 2018-08-02 at 10:56 +0200, Cyril Brulebois wrote:
> debian-installer
> ================
> net-retriever
> -------------
>   https://salsa.debian.org/installer-team/net-retriever/commit/09535b0613a85e02d511b92b60683b20405b6d42

This looks rather inefficient.  Maybe not a big deal for the small
number of udebs though.

(Time to put a more powerful scripting language in the installer?  Even
awk would be a step up!)

> base-installer
> --------------
> We could probably modify library.sh to reuse it, but I'd like to have
> minimal changes (for reasons explained in the very last section). We
> could probably just iterate over all installed linux-image-'*' packages,
> pick the one from the src:linux package, and upgrade it from the
> backports repository.

You mean the src:linux-latest package, right?

This is kind of unfortunate, but should work.  Even when the set of
flavours for a architecture is changed, src:linux-latest builds
transitional packages to support upgrades.

> debian-cd
> =========
> => It might be nice to have some kind of consistency check, at least
>    to make sure the ABI is the same for the linux kernel produced by
>    the d-i build, and for the modules available in the backports
>    suite. [Note: this might be true for weekly builds too, see recent
>    complaints/bug reports.] Bonus points if the source version is
>    checked too, for extra caution.

It is not a nice bonus, but really important that the source version is
equal.  Using module udebs older than the kernel image will usually
(but not always) work, but using newer module udebs will often result
in unresolvable symbols for some modules.

> The finish-install script ran as expected, but I ended up with a 4.16
> kernel from backports in the installed system, as the linux-latest
> binaries still point to it rather than to 4.17 (presumably because
> linux/stretch-backports is still Needs-Build on mipsel at the moment).

That was just forgotten, I'm afraid.  Bastian has just updated linux-

> It was downloaded from the network mirror.
> => It would be nice if we could include the linux-image-* packages from
>    backports (and their dependencies) directly on the installation image,
>    so as to be indpendent of what's happening in the stretch-backports
>    suite on online mirrors.

I agree, it should be possible to install without network sources

>                             Users would have reproducible results over
>    time, instead of a jumpy target. I don't know debian-cd enough to
>    determine how feasible it would be. I'm also not sure what would happen
>    if we had “old” linux-image packages on the ISO, and “newer” ones on
>    mirrors.

If they *do* enable network sources then they should get the latest
version.  This is not so different from installing stable and getting a
security update instead of the version on the installation image.

> Open questions
> ==============
> Now that I've explained (in length…) how it works, I think it's high
> time we define what our target is.
> Due to the volatility of a backports suite, I would tend to not even try
> to support netboot.


>                     Aiming for a least a netinst image would look good
> to me. If we can manage that, we can probably also produce a CD1 for
> those who want to have more packages than just what's on a netinst (I've
> had at least one such request). I'm not going to debate how many
> desktops we should have CD1 for, that's really not my call. I'll just
> mention that size constraints might be tricky since we'll have both the
> linux-image packages for the base suite and those from the backports
> suite. The whole DVD/BR thing is probably entirely overkill.

As I understand it, CD#1 is already fairly useless for non-networked
(or limited network) installations and DVD#1 is a lot more useful.

> => Choice to make: netinst and maybe CD1(s)? Something else?
> It's probably a good idea to consider building matching unofficial
> image(s) with firmwares embedded. I'm not an expert regarding debian-cd
> so help is much welcome. Tweaks might be needed to get firmwares
> installed and/or upgraded from the backports repository, be it to embed
> them on the image, or to make them available to the installed system.

Yes, firmware would need to come from backports.

Since there is no dependency relation between the kernel and firmware
package, I don't prune old files until they are no longer referenced by
the kernel version in any supported suite.  So the CD image build would
only need to use firmware packages from backports, not two different

> Last question: how often do we produce such an image? I don't think it's
> reasonable to do that every time a new major version of linux is made
> available in the backports repository. Doing that once around the middle
> of the release cycle would look good to me. This would kind of mimic the
> “and a half” thing we had in the past. Once we get the process right, we
> might think about doing so another time or two, but we already have limited
> humanpower to deal with stable point releases and alphas for testing
> (at least oldstable is gone now)…

Doing this even once per release is a nice improvement, but I think
it's not enough to solve the problem of unsupported hardware (even on
x86).  And I think the more often this is done, the easier it will get.
 Still, I realise that you are likely to end up doing most of the work,
and only you can decide how much time to spend on it.

> => Question: what to advertise/communicate on? One-shot only is probably
>    a good rule of thumb?

I think what you're proposing is to announce this as a one-off, and not
to immediately make any promises about regular builds.  If so, I agree.


Ben Hutchings
If you seem to know what you are doing, you'll be given more to do.

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