# Is using hydra built package declaratively possible?

**URL:** https://discourse.nixos.org/t/is-using-hydra-built-package-declaratively-possible/6838
**Category:** Help
**Created:** [April 23, 2020, 8:24am UTC](https://discourse.nixos.org/t/is-using-hydra-built-package-declaratively-possible/6838 "2020-04-23T08:24:53Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![573](https://discourse.nixos.org/user_avatar/discourse.nixos.org/573/32/2640_2.png) [@573](https://discourse.nixos.org/u/573)
#### Post date: [April 23, 2020, 8:24am UTC](https://discourse.nixos.org/t/is-using-hydra-built-package-declaratively-possible/6838/1 "2020-04-23T08:24:53Z")

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Hello folks,

I recently learned that you can install packages successfully built on hydra using the `nix-env` call revelead by the Summary \> Build products \> Help Action button.

Is it somehow possible to install that same closure declaratively as in

```auto
(import (builtins.fetchTarball "https://hydra.nixos.org/build/116518901/download/1/cachix") {})

```

How would I determine the corresponding url (i. e. smth like `https://hydra.nixos.org/build/116518901/download/1/cachix` see [this comment](https://discourse.nixos.org/t/concept-use-any-package-version/6515/3)) ?