[Pkg-ltsp-devel] Bug#874775: ltsp: Use of /var/lib/apt/lists internals

[Vagrant Cascadian]

On 2017-09-09, Julian Andres Klode wrote:
> On Sat, Sep 09, 2017 at 04:57:19PM +0200, Petter Reinholdtsen wrote:
>> [Julian Andres Klode]
>> > Instead of relying on internals, please use the interfaces provided by
>> > APT 1.1 and newer:
>> 
>> Very good.  As you might have seen from the URL you sent, LTSP copies
>> the package lists into its chroot to avoid having to download the same
>> set of files again in the chroot.  What is the recommended way to do
>> this using the API interfaces?  Is there a way to "inject" package
>> lists, or should the script get the paths inside and outside the chroot
>> before copying between the paths?


> I'm not entirely sure why you just copy Packages files, but you could
> just do the query for Packages with indextargets and copy them over into
> $ROOT.

Probably because we don't generally care about Sources, and Release
files are small enough that it's worth re-downloading them to make sure
everything is up to date.


> for file in $(apt-get indextargets --format '$(FILENAME)' "Created-By: Packages"); do
> 	mkdir -p $ROOT/"$(dirname "$file")"
> 	cp "$file" "$ROOT/$file"
> done

If the "apt-get indextargets" syntax depends on apt 1.1+, it looks like
this wouldn't be supported on Debian Jessie (apt 1.0.9) or Ubuntu 14.04
(apt 1.0.1). This is not a deal-breaker, per se, but it's worth noting.


Of course, the /var/lib/apt/lists path might actually be different
outside of the chroot than inside, if it's configurable. So inside the
chroot we would need to get the values before copying them:

  dirstate=$(chroot $ROOT apt-config dump Dir::State)

And then parse out Dir::State and Dir::State::Lists and reassemble
inside the chroot.

That said, with a freshly built chroot, how likely is it that the
directory is non-default, or how likely will the default change in the
forseeable future?


> But I guess you also have to copy Release files, I don't see how that
> works well with APT currently. But we don't store Release files
> compressed, so it's sort of OK. Why not just copy everything?

It's been a while since I've used this feature for LTSP, but in my
experience, apt goes ahead and gets whatever files are missing. Maybe
that will change...


live well,
  vagrant
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