mirror of
https://github.com/nix-community/nix-direnv.git
synced 2025-11-08 19:46:11 +01:00
143 lines
3.8 KiB
Markdown
143 lines
3.8 KiB
Markdown
# nix-direnv
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A fast, persistent use_nix implementation for direnv.
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Prominent features:
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- significantly faster after the first run by caching the nix-shell environment
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- prevents garbage collection of build dependencies by symlinking the resulting
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shell derivation in the user's `gcroots` (Life is too short to loose your
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build cache of your project if you are in a plane without internet connection)
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## Installation via nix
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Since 20.03 you can install nix-direnv via nix:
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### NixOS
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In `/etc/nixos/configuration.nix`:
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```
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{ pkgs, ... }: {
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environment.systemPackages = with pkgs; [ nix-direnv ];
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# nix options for derivations to persist garbage collection
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nix.extraOptions = ''
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keep-outputs = true
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keep-derivations = true
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'';
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environment.pathsToLink = [
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"/share/nix-direnv"
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];
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}
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```
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Then source the direnvrc from this repository in your own `.direnvrc`
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```bash
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# put this in ~/.direnvrc
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source $HOME/.nix-direnv/direnvrc
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if [ -f /run/current-system/sw/share/nix-direnv/direnvrc ]; then
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source /run/current-system/sw/share/nix-direnv/direnvrc
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fi
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```
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### Home-manager
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In `$HOME/.config/nixpkgs/home.nix` add
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```
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{ pkgs, ... }:
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home.packages = with pkgs; [
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nix-direnv
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];
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```
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Then add the following lines to your direnvrc:
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```
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if [ -f ~/.nix-profile/share/nix-direnv/direnvrc ]; then
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source ~/.nix-profile/share/nix-direnv/direnvrc
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fi
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```
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Optional: To protect your nix-shell against garbage collection you also need to add these options to your nix configuration
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If you are on NixOS also add the following lines to your `/etc/nixos/configuration.nix`:
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```
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{ pkgs, ... }: {
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nix.extraOptions = ''
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keep-outputs = true
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keep-derivations = true
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'';
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}
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```
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On other systems with nix add the following configuration to your `/etc/nix/nix.conf`:
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```
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keep-derivations = true
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keep-outputs = true
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```
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## Installation via nix-env
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As **non-root** user do the following:
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```console
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nix-env -f '<nixpkgs>' -iA nix-direnv
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```
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Than follow the home-manager installation except for the `$HOME/.config/nixpkgs/home.nix` changes.
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## Installation from source
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Clone the repository to some directory
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```console
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$ git clone https://github.com/nix-community/nix-direnv $HOME/nix-direnv
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```
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Then source the direnvrc from this repository in your own `.direnvrc`
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```bash
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# put this in ~/.direnvrc
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source $HOME/nix-direnv/direnvrc
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```
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## Storing .direnv outside the project directory
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`.direnv` might interact badly with backups (i.e. Dropbox) or IDEs.
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Therefore it's possible to override in `$HOME/.config/direnv/direnvrc` or
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in own project's `.envrc` a variable called `$direnv_layout_dir`.
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The following example will create a unique directory name per project
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in `$HOME/.cache/direnv/layouts/`:
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```bash
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# $HOME/.config/direnv/direnvrc
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: ${XDG_CACHE_HOME:=$HOME/.cache}
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pwd_hash=$(echo -n $PWD | shasum | cut -d ' ' -f 1)
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direnv_layout_dir=$XDG_CACHE_HOME/direnv/layouts/$pwd_hash
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```
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## Known Bugs
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At the moment nix-direnv depends on gnugrep and a modern bash version.
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This might lead to [problems](https://github.com/nix-community/nix-direnv/issues/3) on macOS.
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As a work-around we suggest to install direnv/grep via nix or homebrew.
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## Why not using lorri instead?
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Lorri causes large CPU load when `$NIXPKGS` is pointed to a directory, i.e. a
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git checkout. This is because it tries to watch any referenced nix file and
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re-evaluates if those changes. Nix-direnv comprises between performance and
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correctness and only reevaluate direnv if either the project-specific
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`default.nix` / `shell.nix` changes or if there is a new commit added to
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`nixpkgs`. A re-evaluation can be also triggered by using `touch shell.nix` in
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the same project. Also `nix-direnv` does not require additional software besides
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`direnv` + `nix` i.e. a daemon and the function could be included into the
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project itself.
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