---
title: "Cache"
description: "nix binary cache"
date: 2025-02-26T17:37:19+0100
---

We provide a binary cache in `hut`, with the aim of avoiding unnecessary
recompilation of packages.

The cache should contain common packages from bsckpkgs, but we don't provide
any guarantee that of what will be available in the cache, or for how long.
We recommend following the latest version of the `jungle` flake to avoid cache
misses.

## Usage

### From NixOS

In NixOS, we can add the cache through the `nix.settings` option, which will
enable it for all builds in the system.

```nix
{ ... }: {
  nix.settings = {
    substituters = [ "https://jungle.bsc.es" ];
    trusted-public-keys = [ "jungle.bsc.es:pEc7MlAT0HEwLQYPtpkPLwRsGf80ZI26aj29zMw/HH0=" ];
  };
}
```

### Interactively

The cache can also be specified in a per-command basis through the flags
`--substituters` and `--trusted-public-keys`:

```sh
nix build --substituters "https://jungle.bsc.es/cache" --trusted-public-keys "jungle.bsc.es:pEc7MlAT0HEwLQYPtpkPLwRsGf80ZI26aj29zMw/HH0=" <...>
```

### Nix configuration file (non-nixos)

If using nix outside of NixOS, you'll have to update `nix.conf`

```bash
echo "substituters = https://jungle.bsc.es" >> /etc/nix/nix.conf
echo "trusted-public-keys = jungle.bsc.es:pEc7MlAT0HEwLQYPtpkPLwRsGf80ZI26aj29zMw/HH0=" >> /etc/nix/nix.conf
```

### Hint in flakes

By adding the configuration below to a `flake.nix`, when someone uses the flake,
`nix` will interactively ask to trust and use the provided binary cache:

```nix
{
  nixConfig = {
    extra-substituters = [
      "https://jungle.bsc.es/cache"
    ];
    extra-trusted-public-keys = [
      "jungle.bsc.es:pEc7MlAT0HEwLQYPtpkPLwRsGf80ZI26aj29zMw/HH0="
    ];
  };
  outputs = { ... }: {
    ...
  };
}
```