All (really all?) the opam conf packages are just interfaces to the respective OS
packages,
so you would normally need the package plus the dev-package for it.

Just search with apt-cache, apt-file, or command-not-found (beware the recursion, the
latter two have to be installed :-)

/Str.

On 28.03.2016 05:08, Helmut Brandl wrote:
> I have severe problems installing some packages with opam. I want to install
> 'js_of_ocaml' with opam, but it cannot install the package 'conf-pkg-config'. In
> trying to do this I get the error:
>
>     opam install conf-pkg-config
>     The following actions will be performed:
>       ∗  install conf-pkg-config 1.0
>
>     =-=- Gathering sources =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>
>     =-=- Processing actions -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>     [ERROR] The compilation of conf-pkg-config failed at "pkg-config --help".
>
>     #=== ERROR while installing conf-pkg-config.1.0 ===============================#
>     # opam-version 1.2.2
>     # os           linux
>     # command      pkg-config --help
>     # path         /home/helmut/.opam/4.02.3/build/conf-pkg-config.1.0
>     # compiler     4.02.3
>     # exit-code    127
>     # env-file    
>     /home/helmut/.opam/4.02.3/build/conf-pkg-config.1.0/conf-pkg-config-11348-42bb52.env
>     # stdout-file 
>     /home/helmut/.opam/4.02.3/build/conf-pkg-config.1.0/conf-pkg-config-11348-42bb52.out
>     # stderr-file 
>     /home/helmut/.opam/4.02.3/build/conf-pkg-config.1.0/conf-pkg-config-11348-42bb52.err
>
>
>
>     =-=- Error report -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>     The following actions failed
>       ∗  install conf-pkg-config 1.0
>     No changes have been performed
>
>     =-=- conf-pkg-config.1.0 troobleshooting =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>     => This package relies on external (system) dependencies that may be missing.
>     `opam depext conf-pkg-config.1.0' may help you find the
>        correct installation for your system.
>
>
> The recommended check does not give any information.
>
> I have installed the version 4.02.3 successfully via opam and switched to that version.
>
> Any ideas on how to analyze the problem?
>
> Regards
> Helmut
>