proof-read
Kierán Meinhardt
parent
8d55e7fcb7
commit
c1a3be6091
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@ -13,13 +13,13 @@ summary: >
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# nix-instantiate
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I like NixOS and the way modules work.
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I miss them when I do tasks in other languages,
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which have less power than NixOS, for example
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I miss them when I do tasks in other languages
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that have less power than NixOS, for example
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[Ansible](https://www.ansible.com) and [Terraform](https://www.terraform.io).
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Luckily all these tools can be configured via JSON,
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and Nix can easily create JSON.
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The goto tool for that job is
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The go-to tool for that job is
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[nix-instantiate](https://nixos.org/nix/manual/#sec-nix-instantiate)
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which every NixOS has installed (yeye!).
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@ -33,13 +33,13 @@ different tools that use JSON.
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If you are interessted in a full (or almost full)
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terraform JSON renderer have a look at my
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[terranix project](https://github.com/mrVanDalo/terranix)
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[terranix project](https://github.com/mrVanDalo/terranix).
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## First tests
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Lets look what `nix-instantiate` does.
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We create a file `test1.nix`
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We create a file `test1.nix`:
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```nix
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# file test1.nix
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@ -49,7 +49,7 @@ rec {
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}
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```
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and than we run `nix-instantiate` to render json
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and than we run `nix-instantiate` to render JSON:
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```sh
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$> nix-instantiate --eval --json --strict test1.nix | jq
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@ -60,7 +60,7 @@ $> nix-instantiate --eval --json --strict test1.nix | jq
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}
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```
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Nice! this is expected because it is an example from
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Nice! This is expected because it is an example from
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[the documentation](https://nixos.org/nix/manual/#sec-nix-instantiate).
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## Modules for the win
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@ -100,13 +100,13 @@ in
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result.config
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```
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When running
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When running:
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```sh
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nix-instantiate --eval --strict --json test2.nix --show-trace | jq
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```
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we get the following json.
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We get the following JSON:
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```json
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{
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@ -128,8 +128,8 @@ we get the following json.
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```
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This is almost what we want to see. the `_module` value is not needed.
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So lets remove it with a sanitize function, and move the content path
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to a different file called config.nix
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So let's remove it with a sanitization function, and move the content path
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to a different file called `config.nix`.
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```nix
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# file test3.nix
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@ -159,7 +159,7 @@ in
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(sanitize result.config)
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```
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in `config.nix` we can now focus on the configuration content. And we write it
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In `config.nix` we can now focus on the configuration content. And we write it
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just like we would write a NixOS module.
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```nix
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@ -189,7 +189,7 @@ The result of the now well known command
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nix-instantiate --eval --strict --json test3.nix --show-trace | jq
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```
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looks like the result we want to have.
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looks like the result we want to have:
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```nix
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{
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@ -213,18 +213,18 @@ We can write modules to hide complexity and create very well readable
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strange tooling which is not capable of mapping, filtering
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or hiding complexity.
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## a simple example
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## A Simple Example
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Let's make an example so a none NixOS veteran can see
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Let's make an example so a non-NixOS-veteran can see
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how to start using this modules system.
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### hcloud.nix
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### `hcloud.nix`
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The following file is a module that let's us create
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resource entries to create a
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resource entries to create an
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[hcloud server](https://www.terraform.io/docs/providers/hcloud/r/server.html).
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But it has one parameter `additionalFileSize`
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which will automatic add a `hcloud_volume` and a `hcloud_volume_attachment`.
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which will automatically add an `hcloud_volume` and an `hcloud_volume_attachment`.
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```nix
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# hcloud.nix
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@ -299,11 +299,11 @@ in {
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}
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```
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### config.nix and output
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### `config.nix` and Output
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#### without additionalFileSize
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#### Without `additionalFileSize`
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Lets look at the different `config.nix` results.
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Let's look at the different `config.nix` results.
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```nix
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{
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@ -350,9 +350,9 @@ The `hcloud` parameter should be removed, but for now I will leave it here,
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to see the original configuration.
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To make this work in terraform, you have to remove everything except `resource`.
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#### with additionalFileSize
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#### With `additionalFileSize`
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Lets add some `additionalFileSize`.
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Let's add some `additionalFileSize`.
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```nix
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{
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@ -408,21 +408,21 @@ $> nix-instantiate --eval --strict --json test3.nix --show-trace | jq
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}
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```
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Oha, a lot of other resources joined the party.
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Additionally the `additionalFileSize` parameter is
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Whoa, a lot of other resources joined the party.
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Additionally, the `additionalFileSize` parameter is
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properly removed from `resource.hcloud_server.test`.
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You could also create this very simple example with
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`variables`, `locals` and `count`.
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By doing that you already reached the limits of
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By doing that, you already reached the limits of
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`HCL` but in Nix this is a very simple example.
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## A more complex Example
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## A More Complex Example
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Lets create something you wouldn't be able to do in `HCL`
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anymore.
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Imagine you have a inner circle of admins,
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Imagine you have an inner circle of admins,
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which need access to all machines created.
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So when a machine is created we also add
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all admin keys.
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@ -453,9 +453,9 @@ Let's look at the config first how it would look like.
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}
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```
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### admins.nix
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### `admins.nix`
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But this time `admins` module will not create any `resource` directly.
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But this time the `admins` module will not create any `resource` directly.
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```nix
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# admins.nix
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@ -481,7 +481,7 @@ with lib;
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### hcloud.nix
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These options are used in the `hcloud.nix` file and of course every
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other module you write, where you write which create servers.
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other module you write, where you write which servers to create.
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```nix
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{ config, lib, ... }:
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@ -574,12 +574,12 @@ in {
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The `hcloud.nix` starts to get big now, and it is very similar to the version
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from the privious section.
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Focus on the last section on `mkMerge` and in `config` look closely
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Focus on the last section on `mkMerge` and in `config` look closely
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at the end of the `serverResource` definition.
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### output
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### Output
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Lets look at the resulting JSON
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Let's look at the resulting JSON:
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```json
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$> nix-instantiate --eval --strict --json test3.nix --show-trace | jq
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@ -634,15 +634,15 @@ $> nix-instantiate --eval --strict --json test3.nix --show-trace | jq
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}
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```
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Nice all 3 keys will be created by `hcloud_ssh_key` and they all get wired
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Nice! All 3 keys will be created by `hcloud_ssh_key` and they all get wired
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to the new `hcloud_server`.
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This should give you a feeling how you can maintain your
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`JSON`/`YAML`-configured tools, with `nix-instantiate` and the NixOS module system.
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JSON/YAML-configured tools, with `nix-instantiate` and the NixOS module system.
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Happy Hacking!
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## Thanks
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Thanks to `tv` for his introduction to `nix-instantiate`.
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Thanks to `lassulus` for polishing this article.
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Thanks to `lassulus` and `kmein` for polishing this article.
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