mirror of
https://github.com/daylinmorgan/oizys.git
synced 2024-11-05 01:53:15 -06:00
add related resources
This commit is contained in:
Cole Mickens
parent
2ea0f44eb8
commit
53f4d92a2f
1 changed files with 85 additions and 44 deletions
129
README.md
129
README.md
|
|
@ -1,14 +1,20 @@
|
|||
# nixos-flake-example
|
||||
|
||||
This readme seeks to explain and justify flakes.
|
||||
It also provides an example NixOS config with a supporting `flake.nix`,
|
||||
This readme starts out with an attempt to explain and justify flakes. It also contains
|
||||
some examples of `nix` cli flakes syntax and tips for adopting flakes in your project.
|
||||
|
||||
Finally, [at the end of the readme](#example-nixos-config-with-optional-flake-support)
|
||||
is an example NixOS config with a supporting `flake.nix`,
|
||||
and instructions to build it with *and without* flakes support at the same time.
|
||||
|
||||
Later, it may contain more comprehensive tips about adopting flakes and changes you made need to make to your configuration.
|
||||
|
||||
- [Overview of Flakes (and why you want it)](#overview-of-flakes-and-why-you-want-it)
|
||||
- [The Basics of Flakes](#the-basics-of-flakes)
|
||||
- [Flake Syntax Examples](#flake-syntax-examples)
|
||||
- [Important Related Reading](#important-related-reading)
|
||||
- [Nix CLI - Flakes Usage](#nix-cli---flakes-usage)
|
||||
- [Useful Commands and Examples](#useful-commands-and-examples)
|
||||
- [nixos-rebuild](#nixos-rebuild)
|
||||
- [nix build](#nix-build)
|
||||
- [nix flake](#nix-flake)
|
||||
- [Auto-coercion examples](#auto-coercion-examples)
|
||||
- [Tips for Porting to Flakes](#tips-for-porting-to-flakes)
|
||||
- [Example NixOS Config with optional Flake support](#example-nixos-config-with-optional-flake-support)
|
||||
|
||||
|
|
@ -16,21 +22,11 @@ Later, it may contain more comprehensive tips about adopting flakes and changes
|
|||
|
||||
Flakes is a few things:
|
||||
* `flake.nix`: a Nix file, with a specific structure to describe inputs and outputs for a Nix project
|
||||
* flake inputs can,
|
||||
* point at directories on disk,
|
||||
* track the tip of master of a github repository,
|
||||
* track specific branches of a generic git repos, etc
|
||||
* See [NixOS Wiki - Flakes - Input Schema](https://nixos.wiki/wiki/Flakes#Input_schema) for flake input examples
|
||||
* See [NixOS Wiki - Flakes - Output Schema](https://nixos.wiki/wiki/Flakes#Input_schema) for flake output examples
|
||||
* `flake.lock`: a manifest that "locks" inputs and records the exact versions in use
|
||||
* CLI support for flake-related features
|
||||
* `nix flake update --recreate-lock-file` for updating all inputs and recreating `flake.lock`
|
||||
* `nix flake update --update-input nixpkgs` to update a single input to latest and recording it in `flake.lock`
|
||||
* `nix build /some/dir#some-output` to build the `some-output` attribute in the `/some/dir` project
|
||||
* (more, see the rest of this document for examples)
|
||||
* pure (by default) evaluations
|
||||
* thus the following are disallowed/unused:
|
||||
* `NIX_PATH` and `<nixpkgs>` type constructs
|
||||
* local user nixpkgs config (`~/.config/{nix,nixpkgs}`)
|
||||
* unpinned imports (aka, `fetchTarball` without a pinned `rev`+`sha256`)
|
||||
* pure (by default) evaluations
|
||||
|
||||
This ultimately enables:
|
||||
* properly hermetic builds
|
||||
|
|
@ -42,42 +38,72 @@ This removes the need for:
|
|||
* manually documenting or scripting to ensure `NIX_PATH` is set consistently for your team
|
||||
* the need for the *"the impure eval tree of sorrow"* that comes with all of today's Nix impurities
|
||||
|
||||
## The Basics of Flakes
|
||||
## Important Related Reading
|
||||
|
||||
* [NixOS Wiki - Flakes](https://nixos.wiki/wiki/Flakes)
|
||||
* a somewhat haphazard collection of factoids/snippets related to flakes
|
||||
* particularly look at: **[Flake Schema](https://nixos.wiki/wiki/Flakes#Flake_schema)**, and it's two sections: **[Input Schema](https://nixos.wiki/wiki/Flakes#Input_schema)**, **[Output Schema](https://nixos.wiki/wiki/Flakes#Output_schema)**
|
||||
* [Tweag - NixOS flakes](https://www.tweag.io/blog/2020-07-31-nixos-flakes/)
|
||||
* this article describes how to enable flake support in `nix` and `nix-daemon`
|
||||
* reading this article is a **pre-requisite**
|
||||
* this README.md assumes you've enabled flakes system-wide
|
||||
|
||||
## Nix CLI - Flakes Usage
|
||||
|
||||
Nix is in flakes mode when:
|
||||
1. `nixos-rebuild <cmd> --flake '.#'` is used
|
||||
2. `nix build '.#something'` the hash-tag syntax is used
|
||||
* `--flake` is used with the `nixos-rebuild` command
|
||||
* or, when `nix build` is used with an argument like `'.#something'` (the hash symbol separates the flake source from the attribute to build)
|
||||
|
||||
Note:
|
||||
* Nix flake commands will implicitly take a directory path, it expects a `flake.nix` inside.
|
||||
When in this mode:
|
||||
* Nix flake commands will implicitly take a directory path, it expects a `flake.nix` inside
|
||||
* when you see: `nix build '.#something'`, the `.` means current directory, and `#something` means to build the `something` output attribute
|
||||
|
||||
## Flake Syntax Examples
|
||||
### Useful Commands and Examples
|
||||
#### nixos-rebuild
|
||||
* `nixos-rebuild build --flake '.#'`
|
||||
* looks for `flake.nix` in `.` (current dir)
|
||||
* since it's `nixos-rebuild`, it automatically tries to build:
|
||||
* `#nixosConfigurations.{hostname}.config.system.build.toplevel`
|
||||
* `nixos-rebuild build --flake '/code/nixos-config#mysystem'`
|
||||
* looks for `flake.nix` in `/code/nixos-config`
|
||||
* since it's `nixos-rebuild`, it automatically tries to build:
|
||||
* `#nixosConfigurations.mysystem.config.system.build.toplevel`
|
||||
* (note that this time we specifically asked, and got to build the `mysystem` config)
|
||||
#### nix build
|
||||
* `nix build 'github:colemickens/nixpkgs-wayland#obs-studio'`
|
||||
* looks for `flake.nix` in (a checkout of `github.com/colemickens/nixpkgs-wayland`)
|
||||
* builds and run the first attribute found:
|
||||
* `#obs-studio`
|
||||
* `#packages.{currentSystem}.obs-studio`
|
||||
* TODO: finish fleshing out this list
|
||||
#### nix flake
|
||||
* `nix flake update --recreate-lock-file`
|
||||
* updates all inputs and recreating `flake.lock`
|
||||
* `nix flake update --update-input nixpkgs`
|
||||
* updates a single input to latest and recording it in `flake.lock`
|
||||
|
||||
These three examples, for me, are all the same source, but accessed in different ways:
|
||||
### Auto-coercion examples
|
||||
|
||||
* `nix build '.#nixosConfigurations.mysystem'`
|
||||
Nix CLI will try to be ... smart and auto-coerce some output attribute paths for you.
|
||||
|
||||
(loads `flake.nix` from `.` (current dir))
|
||||
|
||||
* `nix build '/home/cole/code/nixos-flake-example#nixosConfigurations.mysystem'`
|
||||
|
||||
(loads `flake.nix` from `/home/cole/code/nixos-flake-example`)
|
||||
|
||||
* `nix build 'github.com:colemickens/nixos-flake-example#nixosConfigurations.mysystem'`
|
||||
|
||||
(nix will clone my github repo, then load `flake.nix` from `flake.nix` in the root of that repo checkout)
|
||||
|
||||
More auto-coercion:
|
||||
|
||||
1. `nixos-rebuild build --flake '.#'` will automatically try to find and build the attribute: `.#nixosConfigurations.your_hostname` (assuming your machines hostname is `your_hostname`)
|
||||
* `nix build '/some/path#obs-studio'`:
|
||||
* builds and run the first attribute found:
|
||||
* `/some/path#obs-studio`
|
||||
* `/some/path#packages.{pkgs.system}.obs-studio`
|
||||
* TODO: finish fleshing out this list
|
||||
|
||||
## Tips for Porting to Flakes
|
||||
|
||||
* remove sources of impurity
|
||||
* TODO: explain how to fetchTarball pin
|
||||
* TODO: explain how to use flake inputs in config instead of wild fetchTarball
|
||||
* TODO: getFlake vs inputs in specialArgs
|
||||
**Remove Impurities** - Since nix flakes does a 'pure' build by default,
|
||||
* `NIX_PATH` is ignored
|
||||
* `<nixpkgs>` imports do not work, and explicitly error
|
||||
* local user nixpkgs config (`~/.config/{nix,nixpkgs}`) are ignore
|
||||
* unpinned imports (aka, `fetchTarball` without a pinned `rev`+`sha256`) are forbidden
|
||||
|
||||
To fix these:
|
||||
* specify all remote imports in `flake.nix` instead of using `fetchTarball`
|
||||
* TODO: example? example commit of what this looks like for `nixpkgs-wayland`
|
||||
* TODO: investigate `getFlake` vs passing `inputs` in `specialArgs`
|
||||
|
||||
## Example NixOS Config with optional Flake support
|
||||
|
||||
|
|
@ -97,6 +123,9 @@ Let's prove that we can build this config, with and without flakes:
|
|||
readlink -f ./result
|
||||
/nix/store/gg1jhmzqndqa0rfnwfdbnzrn8f74ckr6-nixos-system-mysystem-21.03pre-git
|
||||
|
||||
# !! for this next step, match the git SHA1 to what the flake.lock uses
|
||||
# otherwise you'll have a hash mismatch due to different nixpkgs
|
||||
|
||||
# without flakes
|
||||
export NIX_PATH=nixpkgs=https://github.com/nixos/nixpkgs/archive/007126eef72271480cb7670e19e501a1ad2c1ff2.tar.gz:nixos-config=/home/cole/code/nixos-flake-example/configuration.nix
|
||||
nixos-rebuild build
|
||||
|
|
@ -148,3 +177,15 @@ Let's prove that we can build this config, with and without flakes:
|
|||
clssc: /nix/store/gg1jhmzqndqa0rfnwfdbnzrn8f74ckr6-nixos-system-mysystem-21.03pre-git
|
||||
```
|
||||
|
||||
# Flake Feedback/Ponderings
|
||||
|
||||
- Is the hash tag syntax really worth it?
|
||||
- For example, is:
|
||||
- `nix build 'github:colemickens/nixpkgs-wayland#obs-studio'`
|
||||
- really better than:
|
||||
- `nix build --flake 'github:colemickens/nixpkgs-wayland' 'obs-studio'` ?
|
||||
|
||||
- Are the auto-coercion rules for attribute paths worth it?
|
||||
They definitely add some mental overhead...
|
||||
|
||||
-
|
||||
|
|
|
|||
Loading…
Reference in a new issue