[Nix-dev] [NixOS] How does system.requiredKernelConfig work?

[Shea Levy]

Hello,

On 01/07/2013 05:57 AM, Rickard Nilsson wrote:
> Hi,
>
> The system.requiredKernelConfig configuration option in NixOS should allow
> one to specify kernel config options a module needs. But how is it
> supposed to work? I'm creating a service for FSCache/CacheFiles (caching
> NFS or CIFS files locally) in NixOS, and then I need the following kernel
> config options:
>
>     FSCACHE m/y
>     CACHEFILES m/y
>     NFS_FSCACHE y
>     CIFS_FSCACHE y
>
> so I specified this:
>
> system.requiredKernelConfig = with config.lib.kernelConfig; [
>     (isYes "NFS_FSCACHE")
>     (isYes "CIFS_FSCACHE")
>     (isEnabled "FSCACHE")
>     (isEnabled "CACHEFILES")
> ];
>
> But Nix neither warns me that NFS_FSCACHE and CIFS_FSCACHE is not enabled
> (in the nixpkgs default config), nor does it enable them. If I add them to
> pkgs/os-specific/linux/kernel/linux-x.x.nix and rebuild the kernel,
> everything works fine, but I don't see the point of the NixOS option?

The option is only useful (for now at least) when using 
pkgs.linuxManualConfig, which lets you provide a .config file for your 
kernel instead of using the standard config procedure used by the normal 
nixpkgs kernel builder. The config.lib.kernelConfig functions assume all 
features are enabled for the normal nixpkgs kernel.

>
> Best regards,
>     Rickard Nilsson
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