Re: [MirageOS-devel] Opam Docker Permissions Issue?

[Anil Madhavapeddy <anil@xxxxxxxxxx>]

> On 9 Nov 2016, at 12:29, Compos Min <composmin@xxxxxxxxxxxx> wrote:
> 
> Hi Folks,
> I've been reading about Mirage for quite a while now and would like to start 
> making
> some contributions (well as much as somebody that is just learning OCaml).
> 
> Unfortunately I'm stuck on build problem with the simple Dockerfile listed on 
> https://github.com/ocaml/opam-dockerfiles.
> 
> FROM ocaml/opam:ubuntu-15.10_ocaml-4.02.3
> RUN opam remote add dev git://github.com/mirage/mirage-dev
> RUN opam depext -i mirage
> 
> The error output is:
> Fatal error:
> # opam-version    1.2.2 (c968888614d3fdbac881d3b7b8ef32ee97839807)
> # os              linux
> opam: "open" failed on /home/opam/.opam/log/command-5-5a61c5.out: Permission 
> denied

Hi Chris,

I've still not fully documented those Dockerfiles are meant to be used as base 
images, so my apologies for that [1].  I ran through yours and hit a few 
issues, so I thought it might be useful to list out what I did while debugging 
it.

- Your Dockerfile uses Ubuntu 15.10 which is no longer maintained, and so the 
OPAM repository in that image has not been successfully rebuilt since Jun16 
[2].  This leads to an outdated opam-repository package set.  How did I 
diagnose this?

  - The symptom of an outdated opam-repository is that "opam depext mirage" 
installed mirage.2.9.0 despite the mirage-dev remote being available.
  - I changed the RUN line to "opam depext -ui mirage.dev~mirage" to force it 
to explicitly install the development version.
  - This resulted in an OPAM constraint error complaining that "topkg>=0.8.0" 
was not a valid package.  Since that has been released in the past few months, 
the missing package indicated that the repository was out of date.

- I changed it to "ocaml/opam:ubuntu-16.04_ocaml-4.02.3" which is the LTS, and 
reran it. This time the OPAM repository was up-to-date, but the development 
version of Mirage now requires 4.03.0 and so compilation failed.
  - Fixing it on 4.02 is fairly low hanging so I submitted a PR [3]
  - We need to be consistent about our decision on the minimum OCaml version [4]

So recommendations right now for the Dockerfile are:

FROM ocaml/opam:ubuntu-16.04_ocaml-4.03.0
RUN opam remote add dev git://github.com/mirage/mirage-dev
RUN cd /home/opam/opam-repository && git pull -u && opam update -uyv
RUN opam depext -uivy mirage.dev~mirage

This will update the OPAM repository, update the revisions to be the very 
latest, and verbosely install external dependencies.  I'll work on documenting 
this properly in [1] for release documentation.

As for your original permissions issue -- I'm not sure :-)  Are you using 
Docker for Mac by any chance?  That does UID rewriting for shared volumes, but 
I'm otherwise not sure how root crept in here. Could you try adding a "USER 
opam" beforehand to make sure this is working ok?

[1] Dockerfile doc tracking issue: https://github.com/mirage/mirage/issues/697
[2] How do we retire old distributions? 
https://github.com/ocaml/infrastructure/issues/7
[3] https://github.com/mirage/mirage/pull/695
[4] https://github.com/mirage/mirage/issues/696

regards,
Anil


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