[opam-devel] opam binary snapshot

[Sylvain Le Gall]

2013/10/31 Jon Ludlam <jonathan.ludlam at eu.citrix.com>:
> On 31/10/13 12:40, Anil Madhavapeddy wrote:
>> On 15 Oct 2013, at 00:36, Mika Illouz <mika at illouz.net> wrote:
>>
>>> Our current system involves packaging up OCaml stuff as
>>> debian packages, and distributing them to ubuntu clients in binary
>>> form via a internal debian repo.  This gets the ocaml dependencies
>>> necessary to build stuff, even to those don't develop in ocaml, with
>>> minimal cognitive overload.
>>>
>>> Some of my colleagues think that distributing ocaml dependencies in
>>> binary form is ultimately more stable.  I am wondering whether I can
>>> satisfy them, with a solution that somehow exports as binary snapshot
>>> of everything under ~/.opam/4.01/  .  One idea is to define a debian
>>> package for a blessed ~/.opam/4.01/ , and export it via our internal
>>> debian repo.  Another idea is just export it to clients via rsync, or
>>> some other shared global storage.
>> [Ccing opam-devel and also Citrix/Rackspace folk, as this came up
>> last week in XenSummit).
>>
>> In general, I'd like to figure out how to use OPAM to build RPMs and
>> Debs just as easily as it can currently do ocamlfind installations.
>> In the short-term, I suspect that if you use a system compiler and
>> have enough external dependency information in the OPAM repository,
>> we could get away with quite a lot by tarring up the .opam directory.
>>
>> This has also been a frequent request for teaching purposes, so I'd
>> like to experiment with version controlling .opam -- this would just
>> require hooks when adding/creating files in the subdirectory hierarchy,
>> although it would probably be too slow to shell out every time
>> (Thomas' cagit OCaml library may come in useful here).
>>
>> Dave/Jon/John, any thoughts on this?
>>
>> -anil
>
> RPMs/debs would definitely be nice. There would be a problem doing this
> right now as you'd have to do some sort of two pass thing to get the
> list of files installed by the package, which is required for both RPMs
> and debs.
>

You don't need the list of files for a Debian package.... You don't
even need the dependencies, since it is auto-computed (except for
depending on executable, but this is a minor annoyance, lib deps are
computed).

Maybe you are talking about directly generating a binary .deb ? (like
directly an ar archive, but that is super tricky to do)

> One slightly odd thing about tarring up the .opam directory is that it's
> usually something that lives in a user's home directory. I wonder if any
> of the packages might have hard-coded paths in there which would mean
> having to install it into exactly the same place - so requiring the same
> user. I guess a quick grep through the .opam dir would tell you this.
>

Packages use hard coded paths. Most of the things that loads data in
fact (just an example: camomile). When the software has already gone
through a Debian packaging process, you should have a reliable
DESTDIR, but that is not 100% sure.

Regards
Sylvain