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Re: Layers for the package manager

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Le duodi 22 brumaire, an CCXXV, Eduardo M KALINOWSKI a écrit :
>							    Also, if I
> wanted to run another program from stable, I could build another docker
> image for that, but due to the clever way docker works, there'd be only
> one copy of the base system plus two layers, one for each image, with
> only the applications in question. That's a big advantage in relation to
> chroots or virtual machines.

I did not know Docker worked that way. It is interesting, and better
than I thought.

> And yet, even if a base layer is shared, docker images are completely
> isolated from one another and from the host system. If you want to share
> data, you need to explicitly configure that.
> 
> That does solve the isolation problem, and allows you to run packages
> from different repositories simultaneously, with different versions of
> libraries if necessary; and allows you to install packages from
> untrusted sources (or that are not available as .deb's) without messing
> with your "real" system.
> 
> It does not solve the problem you mention: if there is an update of
> OpenSSL, the images will continue to use the old version unless you
> rebuild them. The process can be automated, but at least you'll need to
> run a command to rebuild the images, and this can be time consuming.

Indeed. Compared to what I have in mind, it seems it would work for the
leaves/sinks of the graph system, but not the inner nodes.

Also, the isolation is kind of a mis-feature in this particular case

> Now might be a good time to dive into some of the internals, such as how
> the images and layers work:
> https://docs.docker.com/engine/userguide/storagedriver/imagesandcontainers/
> That might give you some ideas for your solution. Take a look also at
> the pages "AUFS storage driver in practice" and "OverlayFS storage in
> practice". While you won't be able to do what you want with docker,
> perhaps you can get some ideas. I'd guess you'd need some kind of
> layering like done by docker, but sometimes changing the bottom layers
> (which is not possible with docker - only the topmost layer is ever
> changed).

Thanks for the pointers. I definitely do not have time to actually work
on it as a project, but knowing a few pointers will do no harm.
Union-capable filesystems were indeed something that I thought could
help an hypothetic implementation.

Regards,

-- 
  Nicolas George

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Thread

Layers for the package manager Nicolas George <george@nsup.org> - 2016-11-11 20:40 +0100
  Re: Layers for the package manager Eduardo M KALINOWSKI <eduardo@kalinowski.com.br> - 2016-11-11 23:30 +0100
    Re: Layers for the package manager Nicolas George <george@nsup.org> - 2016-11-12 21:20 +0100
      Re: Layers for the package manager Eduardo M KALINOWSKI <eduardo@kalinowski.com.br> - 2016-11-12 22:10 +0100
        Re: Layers for the package manager Nicolas George <george@nsup.org> - 2016-11-17 11:00 +0100
      Re: Layers for the package manager Jonathan Dowland <jmtd@debian.org> - 2016-11-14 18:50 +0100
  Re: Layers for the package manager Don Armstrong <don@debian.org> - 2016-11-15 18:30 +0100
    Re: Layers for the package manager Nicolas George <george@nsup.org> - 2016-11-17 10:50 +0100
      Re: Layers for the package manager Don Armstrong <don@debian.org> - 2016-11-17 16:30 +0100

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