The CUDA Toolkit is a suite of CUDA libraries and software meant to provide a development environment for CUDA-accelerated applications. Until the release of CUDA 11.4, NVIDIA had only made the CUDA Toolkit available as a multi-gigabyte runfile installer, which we provide through the [`cudaPackages.cudatoolkit`](https://search.nixos.org/packages?channel=unstable&type=packages&query=cudaPackages.cudatoolkit) attribute. From CUDA 11.4 and onwards, NVIDIA has also provided CUDA redistributables (“CUDA-redist”): individually packaged CUDA Toolkit components meant to facilitate redistribution and inclusion in downstream projects. These packages are available in the [`cudaPackages`](https://search.nixos.org/packages?channel=unstable&type=packages&query=cudaPackages) package set.

All new projects should use the CUDA redistributables available in [`cudaPackages`](https://search.nixos.org/packages?channel=unstable&type=packages&query=cudaPackages) in place of [`cudaPackages.cudatoolkit`](https://search.nixos.org/packages?channel=unstable&type=packages&query=cudaPackages.cudatoolkit), as they are much easier to maintain and update.

### Updating CUDA redistributables {#updating-cuda-redistributables}

1. Go to NVIDIA's index of CUDA redistributables: <https://developer.download.nvidia.com/compute/cuda/redist/>
2. Make a note of the new version of CUDA available.
3. Run

   ```bash
   nix run github:connorbaker/cuda-redist-find-features -- \
      download-manifests \
      --log-level DEBUG \
      --version <newest CUDA version> \
      https://developer.download.nvidia.com/compute/cuda/redist \
      ./pkgs/development/cuda-modules/cuda/manifests
   ```

   This will download a copy of the manifest for the new version of CUDA.
4. Run

   ```bash
   nix run github:connorbaker/cuda-redist-find-features -- \
      process-manifests \
      --log-level DEBUG \
      --version <newest CUDA version> \
      https://developer.download.nvidia.com/compute/cuda/redist \
      ./pkgs/development/cuda-modules/cuda/manifests
   ```

   This will generate a `redistrib_features_<newest CUDA version>.json` file in the same directory as the manifest.
5. Update the `cudaVersionMap` attribute set in `pkgs/development/cuda-modules/cuda/extension.nix`.

### Updating cuTensor {#updating-cutensor}

1. Repeat the steps present in [Updating CUDA redistributables](#updating-cuda-redistributables) with the following changes:
   - Use the index of cuTensor redistributables: <https://developer.download.nvidia.com/compute/cutensor/redist>
   - Use the newest version of cuTensor available instead of the newest version of CUDA.
   - Use `pkgs/development/cuda-modules/cutensor/manifests` instead of `pkgs/development/cuda-modules/cuda/manifests`.
   - Skip the step of updating `cudaVersionMap` in `pkgs/development/cuda-modules/cuda/extension.nix`.

### Updating supported compilers and GPUs {#updating-supported-compilers-and-gpus}

1. Update `nvccCompatibilities` in `pkgs/development/cuda-modules/_cuda/data/nvcc.nix` to include the newest release of NVCC, as well as any newly supported host compilers.
2. Update `cudaCapabilityToInfo` in `pkgs/development/cuda-modules/_cuda/data/cuda.nix` to include any new GPUs supported by the new release of CUDA.

### Updating the CUDA Toolkit runfile installer {#updating-the-cuda-toolkit}

> **WARNING**
>
> While the CUDA Toolkit runfile installer is still available in Nixpkgs as the [`cudaPackages.cudatoolkit`](https://search.nixos.org/packages?channel=unstable&type=packages&query=cudaPackages.cudatoolkit) attribute, its use is not recommended and should it be considered deprecated. Please migrate to the CUDA redistributables provided by the [`cudaPackages`](https://search.nixos.org/packages?channel=unstable&type=packages&query=cudaPackages) package set.
>
> To ensure packages relying on the CUDA Toolkit runfile installer continue to build, it will continue to be updated until a migration path is available.

1. Go to NVIDIA's CUDA Toolkit runfile installer download page: <https://developer.nvidia.com/cuda-downloads>