Functional package manager. Supports easy rollbacks. Language for interacting with nix package manager. NixOS - OS based on nix. Can facilitate deployments on remote machines with nixops. Here are some scattered notes about the topic.

nix-shell

Create temporary environments

nix-shell -p prog1 prog2
nix-shell 'expr'

{ pkgs ? import <nixpkgs> {} }:
  pkgs.mkShell {
    buildInputs = [ pkgs.hello ];
}

# Or
{ pkgs ? import <nixpkgs> {} }:
  pkgs.mkShell with pkgs; {
    buildInputs = [ hello ];
}

Composes pretty well with direnv. Or even better - use lorri instead of nix-shell.

Pinned nix shell

We would like a easy-to-pin shell.nix with overriding packages. Here it is (Nix 2.0 +).

shell.nix:

let
  java = "openjdk8_headless";
  pkgs = import ./nix/pkgs.nix { inherit java; };
in pkgs.mkShell {
  buildInputs = [ pkgs.${java} pkgs.sbt ];

  shellHook = ''
    export JAVA_HOME="${pkgs.${java}}"
  '';
}

nix/pkgs.nix:

{ java }:

let
  pinnedPkgs = (fetchTarball
    "https://github.com/NixOS/nixpkgs/archive/d3f7e969b9860fb80750147aeb56dab1c730e756.tar.gz");
  config = {
    packageOverrides = p: {
      jdk = p.${java};
      jre = p.${java};
    };
  };
in import pinnedPkgs { inherit config; }

More info about pinning nixpkgs here.

nix-store

# find related packages to nix path (man nix-store for more)
nix-store --query (--referrers[-closure]|--references) <nix-path>


# delete nix path
nix-store --delete [--ignore-liveness] /nix/store/<...>

# --ignore-liveness - skip checking if package is in use.

People advise using sudo to force deletion. Keep in mind that it could change owner of /nix/store to root. If installed nix in single-user mode - you have to bring it back (and probably don’t need sudo in first place 😏).

nix-du

With nix-du we can (somewhat) visualize dependency tree.

nix-du -s=10MB | tred | dot -Tsvg > ~/store.svg

Diff home-manager generations

# requires awk, diff, delta (by default)
generation() {
	home-manager generations | awk -v id="$1" '$5 == id {print $NF}'
}

after=204
before=203

after_nix="$(generation $after)"
before_nix="$(generation $before)"
nix-store -qR $after_nix > /tmp/after_nix
nix-store -qR $before_nix > /tmp/before_nix

diff -u /tmp/before_nix /tmp/after_nix | delta

Recipes

Nix check packages version / hash

nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'

Build package

nix-build -E 'with import <nixpkgs> { }; callPackage ./zap/default.nix { }'

Use self-writen package

home.packages = [
    callPackage ./zap/default.nix { }
];

Search packages

nix-env -qaPA nixpkgs.nodePackages #search in nodePackages

nix search <package>

Cleanup nix-store

To cleanup old generations we should(probably 😼)

  • remove old home-manager generations: home-manager expire-generations "-2 days"
  • run nix-collect-garbage [-d | --delete-older-than "30d"] -d deletes all non-current generations (not allowing rollbacks)

NixOS

Fix command-not-found failing with sqlite errors

https://discourse.nixos.org/t/command-not-found-unable-to-open-database/3807/5