[Nix-dev] [Nix-commits] [NixOS/nixos] b609ff: allow out-of-tree nixos modules

[Mathijs Kwik]

Nicolas Pierron <nicolas.b.pierron at gmail.com> writes:

> Hi all,
>
> I wrote a bit of documentation to for people who cannot understand
> NixOS logic.  You might find main use case of modules described on
>
>     https://nixos.org/wiki/NixOS:Modules

That's a nice overview!
I just thought configuration.nix and other "no-declaration" modules were
just the config attribute of a "full module". Reading the source (which
is in nixpkgs, not nixos) made it clear eventually, but this wiki page
sums it up nicely.

Thanks!

>
> On Sat, Jul 21, 2012 at 9:25 AM, Mathijs Kwik <mathijs at bluescreen303.nl> wrote:
>> Ah :)
>>
>> I did read the sources of lib/eval-config and saw that
>> configuration.nix is just treated as a module, so I did understand
>> that part. However it wasn't clear to me how to use that to add
>> additional modules (config option "modules" of course doesn't exist).
>
> The reason is that modules are filtered to avoid duplicates and this
> option may cause the evaluation of a configuration to have no
> fix-point.
> In addition, of having no fix-point, this is likely to cause a huge
> memory consumption compared to our current system, which does not do
> that well right now.
>
>> But indeed, now it's clear. Didn't see lib/modules in nixpkgs yet.
>> Quite ingenious :)
>
> Thanks, I think I will keep this email around for the bad days :)
>
>> I'll revert my commit.
>>
>> On Sat, Jul 21, 2012 at 6:11 PM, Shea Levy <shea at shealevy.com> wrote:
>>> Nope, it works for both. 'configuration files' are actually a
>>> special case of a module (a module that has no options and
>>> unconditionally sets other options).
>>>
>>> On Jul 21, 2012, at 12:05 PM, Mathijs Kwik <mathijs at bluescreen303.nl> wrote:
>>>> As I understood, "require" is for including configuration files (that
>>>> set options).
>>>>
>>>> This new option allows adding modules, leading to new options to configure.
>>>>
>>>> On Sat, Jul 21, 2012 at 6:00 PM, Shea Levy <shea at shealevy.com> wrote:
>>>>> How does the 'require' option not suit this need?
>>>>>
>>>>> On Jul 21, 2012, at 11:38 AM, Mathijs Kwik <mathijs at bluescreen303.nl> wrote:
>>>>>> The environment variable "NIXOS_EXTRA_MODULES" is now checked to
>>>>>> contain a path to a file similar to modules/module-list.nix.
>
> You might find some examples in my laptops configurations:
>

I browsed all you guys' configs a bit after Michael pointed me to that repo.
Fortunately it's all quite similar to what I'm doing :)


> https://nixos.org/repos/nix/configurations/trunk/misc/nicolas.b.pierron/
>
> I made a few modules in the common directory which are included in
> most of my configurations.  Which was the first reason of NixOS module
> system ;)

Have a nice weekend,
Mathijs