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The kernel derivation created with `pkgs.buildLinux` exports an attribute `features` specifying whether optional functionality is or isn’t enabled. This is used in NixOS to implement kernel-specific behaviour.

     

       
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:::{.example #ex-skip-package-from-kernel-feature}

     

       
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# Skipping an external package because of a kernel feature

     

       
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For instance, if the kernel has the `iwlwifi` feature (i.e., has built-in support for Intel wireless chipsets), then NixOS doesn’t have to build the external `iwlwifi` package:

     

       
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```nix

     

       
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modulesTree = [kernel]

     

       
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  ++ pkgs.lib.optional (!kernel.features ? iwlwifi) kernelPackages.iwlwifi

     

       
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  ++ ...;

     

       
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```

     

       
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:::

     

       
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If you are using a kernel packaged in Nixpkgs, you can customize it by overriding its arguments. For details on how each argument affects the generated kernel, refer to [the `pkgs.buildLinux` source code](https://github.com/NixOS/nixpkgs/blob/d77bda728d5041c1294a68fb25c79e2d161f62b9/pkgs/os-specific/linux/kernel/generic.nix).

     

       
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:::{.example #ex-overriding-kernel-derivation}