# Installing a single stable package when on unstable?

**URL:** https://discourse.nixos.org/t/installing-a-single-stable-package-when-on-unstable/68021
**Category:** Help
**Created:** [August 15, 2025, 10:17am UTC](https://discourse.nixos.org/t/installing-a-single-stable-package-when-on-unstable/68021 "2025-08-15T10:17:14Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![Oneechan69](https://discourse.nixos.org/user_avatar/discourse.nixos.org/oneechan69/32/32401_2.png) [@Oneechan69](https://discourse.nixos.org/u/Oneechan69)
#### Post date: [August 15, 2025, 10:17am UTC](https://discourse.nixos.org/t/installing-a-single-stable-package-when-on-unstable/68021/1 "2025-08-15T10:17:14Z")

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I’m on unstable for newer package versions. In my flake I have `nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";`. A [PR](https://github.com/NixOS/nixpkgs/pull/433196) to [fix rust-analyzer](https://github.com/NixOS/nixpkgs/issues/432960) got merged but its not up yet so it fails to build for me right now.

I looked up how to install a single stable package and found [this solution](https://discourse.nixos.org/t/installing-only-a-single-package-from-unstable/5598/4) for a single unstable package which I copied below. If I were to use this then how would I get the tarball URL for a specific nixpkgs version, like 25.05 for example? or is there another (possible better) way to do this?

```
# configuration.nix
{ config, pkgs, ... }:
let
  unstable = import
    (builtins.fetchTarball https://github.com/nixos/nixpkgs/tarball/<branch or commit>)
    # reuse the current configuration
    { config = config.nixpkgs.config; };
in
{
  environment.systemPackages = with pkgs; [
    nginx
    unstable.certbot
  ];
}

```

---

<div class="post-metadata">

### Author: ![picnoir](https://discourse.nixos.org/user_avatar/discourse.nixos.org/picnoir/32/4186_2.png) [@picnoir](https://discourse.nixos.org/u/picnoir)
#### Post date: [August 15, 2025, 10:21am UTC](https://discourse.nixos.org/t/installing-a-single-stable-package-when-on-unstable/68021/2 "2025-08-15T10:21:21Z")

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The PR did not reach the nixos-unstable channel yet. You can track the progress using nixpk.gs: [Nixpkgs PR #433196 ("rust-analyzer-unwrapped: fix source hash") progress](https://nixpk.gs/pr-tracker.html?pr=433196)

Edit: to be more specific, here, for this particular one, you can use the `nixos-unstable-small` branch to get the fix.

---

<div class="post-metadata">

### Author: ![waffle8946](https://discourse.nixos.org/user_avatar/discourse.nixos.org/waffle8946/32/27221_2.png) [@waffle8946](https://discourse.nixos.org/u/waffle8946)
#### Post date: [August 15, 2025, 11:03am UTC](https://discourse.nixos.org/t/installing-a-single-stable-package-when-on-unstable/68021/3 "2025-08-15T11:03:06Z")

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No, it’s reached, that tracker is just behind. I prefer to use @ocfox’s as it uses github apis directly: [https://nixpkgs-tracker.ocfox.me/?pr=433196](https://nixpkgs-tracker.ocfox.me/?pr=433196)