Nix same; same not different

NIXNIX
SAME; SAMESAME; SAME NOTNOT DIFFERENTDIFFERENT
@Keidrych Anton@Keidrych Anton

REMINDER:REMINDER:
DEPENDENCY HELLDEPENDENCY HELL
“When people stop valuing simplicity over complexity“When people stop valuing simplicity over complexity
~ Barbara Liskov”~ Barbara Liskov”

SOLVEDSOLVED
via Atomicity / Transactionalityvia Atomicity / Transactionality
via System Rollback / Versioningvia System Rollback / Versioning
Provided Atomicity / Transactionality existsProvided Atomicity / Transactionality exists
State of system is justState of system is just versioned snapshotsversioned snapshots
Package manager = transition functionPackage manager = transition function
betweenbetween snapshotssnapshots

WHY SO MUCH PAIN?WHY SO MUCH PAIN?
Filesystem Hierarchy Standard (FHS) - via Linux -Filesystem Hierarchy Standard (FHS) - via Linux -
fundamentally incompatible with reproducibilityfundamentally incompatible with reproducibility
Version?Version?
Libraries used?Libraries used?
Flags during build?Flags during build?

NIXNIX
“NIX can be the future of computing… if we can nd a“NIX can be the future of computing… if we can nd a
better way to explain it ~ Burke Libbey”better way to explain it ~ Burke Libbey”

EXPLAININGEXPLAINING
Maintenance / Upgrading a carMaintenance / Upgrading a car
Debian et al: Working on your car in yourDebian et al: Working on your car in your
own garage… results can varyown garage… results can vary
NIX: 3D Printing a new car every timeNIX: 3D Printing a new car every time
something changessomething changes

SDLC NIRVANASDLC NIRVANA
Same Dev Environment for all DevelopersSame Dev Environment for all Developers
Same CI Environment for all jobsSame CI Environment for all jobs
Not Di erent Code Paths in ProductionNot Di erent Code Paths in Production
&&&& CompliantCompliant12 Factor12 Factor GitOpsGitOps

SDLC NIRVANASDLC NIRVANA
IsolateIsolate directorydirectory from OS via Shellfrom OS via Shell
Install DependenciesInstall Dependencies
BuildBuild
RunRun
Debug ToolingDebug Tooling
Enable Development ModeEnable Development Mode

1:1:
— DirEnv - unclutter your .pro le
DIRENVDIRENV
[direnv] augments existing shells with a[direnv] augments existing shells with a
new feature that can load and unloadnew feature that can load and unload
environment variables depending onenvironment variables depending on
the current directory.the current directory.

ENABLEENABLE
viavia nix env i nixpkgs.direnvnix env i nixpkgs.direnv
~/.bashrc
.envrc
RunRun direnv allowdirenv allow rst time entering directoryrst time entering directory
# Add as last shell manipulation at end of file
eval "$(direnv hook bash)"
use nix
watch_file shell.nix

2:2:
Development replacement forDevelopment replacement for nix shellnix shell
Tracks Global Nix Channel updatesTracks Global Nix Channel updates
Protects directory from premature GarbageProtects directory from premature Garbage
CollectionCollection
Editor Integration via DirEnvEditor Integration via DirEnv
LORRILORRI

ENABLEENABLE
viavia nix env i lorrinix env i lorri
Foreground:Foreground: lorri watchlorri watch
Daemon:Daemon:
services.lorri.enable = trueservices.lorri.enable = true
lorri initlorri init

shell.nix
{ pkgs ? import <nixpkgs> {} }:
pkgs.mkShell {
buildInputs = [
pkgs.hello
# keep this line if you use bash
pkgs.bashInteractive
];
}

3: DEPENDENCIES3: DEPENDENCIES
Option(s)Option(s)
Channels:Channels: nix channelnix channel - Users subscribe- Users subscribe
to your/to your/nixpkgsnixpkgs latest published updateslatest published updates
fetchX:fetchX: ||||
Nix:Nix: - New World -- New World - stabilizingstabilizing --
Hermetic & reproducible evaluationHermetic & reproducible evaluation
nivniv nix-wranglenix-wrangle
Nix FlakesNix Flakes

FETCHXFETCHX
/nix/default.nix
let
sources = import ./sources.nix;
callPackage = (import sources.nixpkgs {}).callPackage;
in
import sources.nixpkgs {
overlays = [
(
final: prev: {
dockerTools = (import sources.pinnedDockerTools {}).docke
k6 = prev.k6.overrideAttrs (
old: {
name = "patched-k6-${old.version}";
src = sources.k6;
}
);
s6-overlay = sources.s6-overlay;

shell.nix
Update to latest SHA of Git Branches viaUpdate to latest SHA of Git Branches via
{ pkgs ? import ./nix }:
with pkgs;
mkShell rec
{
name = "impureEnv";
buildInputs = [ hello ];
}
niv update

SAME (NOT) SAMESAME (NOT) SAME
Build:Build: nix buildnix build
Run:Run: nix shell (execute binary)nix shell (execute binary)
Debug Tooling: bundled viaDebug Tooling: bundled via shell.nixshell.nix
Dev Mode: viaDev Mode: via direnv / lorridirenv / lorri
Hermetic:Hermetic: maybemaybe

FLAKESFLAKES
— https://github.com/NixOS/rfcs/pull/49
Flakes allow hermetic, reproducibleFlakes allow hermetic, reproducible
evaluation of multi-repository Nixevaluation of multi-repository Nix
projects; impose a discoverable,projects; impose a discoverable,
standard structure on Nix projects; andstandard structure on Nix projects; and
replace previous mechanisms such asreplace previous mechanisms such as
Nix channels and the Nix search pathNix channels and the Nix search path

Runnable applicationsRunnable applications nix (name)nix (name)
Tests stdout = stdoutTests stdout = stdout
NixOS ModulesNixOS Modules
CI Linked build to publish versionsCI Linked build to publish versions
to Nix 1.xto Nix 1.x
Cachix integratedCachix integrated
BackportedBackported
Flake UtilsFlake Utils

ake.nix
Update to latest SHA of Git Branches viaUpdate to latest SHA of Git Branches via
{
description = "impureEnv";
inputs.flake-utils.url = "github:numtide/flake-utils";
inputs.nixpkgs.url = "github:NixOS/nixpkgs-channels?rev=72b9660
inputs.pinnedDockerTools.url = "github:xxxxx";
inputs.pinnedDockerTools.flake = false;
# s6-overlay & k6 same process as dockerTools
outputs = { self, nixpkgs, flake-utils }:
let
overlay = final: prev: {
dockerTools = (import pinnedDockerTools {}).dockerTools;
k6 = prev.k6.overrideAttrs (
old: {
name = "patched-k6-${old.version}";
nix flake update --recreate-lock-file

SAME (NOT) SAMESAME (NOT) SAME
Build:Build: nix buildnix build
Run:Run: nix developnix develop
Debug Tooling: bundled viaDebug Tooling: bundled via shell.nixshell.nix
Dev Mode: viaDev Mode: via direnv / lorridirenv / lorri
Hermetic: alwaysHermetic: always

Nix same; same not different

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