Re: updating list of substitutes

[Pjotr Prins <pjotr.public12@thebird.nl>]

On Tue, Apr 21, 2015 at 10:22:48AM +0200, Ludovic Courtès wrote:
> Pjotr Prins <pjotr.public12@thebird.nl> skribis:
> 
> > Pretty much every time I want to install a package I get a search for
> >
> >   updating list of substitutes 
> >
> > being on a slow internet line this sucks (not everyone has fast
> > internet! Think outside the US/Europe where internet is often still
> > metered on mobile lines), besides installing the same software often
> > install a host of new versions of dependencies. I don't like the
> > system changing under me - that is not a reproducible setup.
> >
> > Q1: Do we retain older builds of binaries for some time for download?
> 
> Yes, but the amount of time is unspecified.
> 
> On hydra.gnu.org it can be quite long in practice, so that would call in
> favor of increasing the default TTL in ???guix substitute???.
> 
> In the longer run, we need servers to advertise their TTL (someone
> running ???guix publish??? may have a different TTL.)
> 
> > Q2: Can we switch off updating list of substitutes? A command line
> >     switch would do. '--no-update-supstitutes'
> 
> No.

Can we have that option?

> > Q3: Would it be possible to version the list of substitutes and use
> >     that for (re)deployment? That way I can truely regenerate an existing
> >     system.
> 
> You can always regenerate an existing system.  The list of substitutes
> reflects what???s currently available on hydra.gnu.org.  If some
> substitutes vanish, Guix automatically falls back to building from
> source.

How do I recreate the exact same system from Hydra? Even now if I
install the exact same Ruby-2.2.1 it will install different packages
compared to yesterday.

We could solve it by giving the list of substitutes a HASH and able to
select that and install.

Pj.