Start reading here: http://lethalman.blogspot.si/2014/07/nix-pill-1-why-you-should-give-it-try.html

Intro

• entries in /nix/store are immutable
• /nix/store itself is mutable, but subject to liveness constraints
• nix-collect-garbage
• liveness?
  • entries in the store depend on other entries (there is a database)
  • entries don't depend on anything else
    • no global state
    • no /usr/lib, /usr/bin
    • no /usr/share/..
    • no $PATH!
  • this means we can take a closure and ship it
  • there are roots
    • profiles
    • generations

nix-env

• nix-env -q
• nix-env -i nix-repl
• nix-env --help
• there are generations
• how does it work?
  • symlink farm

nix-store

• low level queries and manipulation
• e.g. list closure for package x
• dump package into a file
• query dependencies
• collect garbage

nix-channel

• where <nixpkgs> comes from
• nix-channel --help
• zengrc is not using this mechanism in order to avoid "it work on my machine"

Nix - the language

• lazy, purely functional, dynamically typed
  • kind of like an ML
  • yes pure, building stuff is done outside the language, fetching dependencies is protected by a hash
• space for application: f x
• string interpolation "${foo}bar"
• ''multiline strings''
• [ funky "list" "syntax ] # no commas
• { foo: "bar"; "baz" = quux; nested.thingy = 1 }
  • called sets, actually more like python dicts
  • yes, semicolons
  • lazy again
  • rec { foo = 1; bar = foo; }
• if a then b else c is an expression
• let a = b; c = d; in a + c
• let longNameHere = { a = 1; b = 2; }; in with longNameHere; a + b
• addOne = x: x + 1
• curried: add = a: b: a+b
• "destructuring" or "arguments set": add = {a, b ? 1, ... }: a + b
• import is an expression x = import ./x

Derivations

• there is a built-in function derivation but we are not going to go this low level read the nix pill 6 and on to understand how it works. We are going to use the stdlib helper nixpkgs.stdenv.mkDerivation
• example1.nix:
  • simplest way is the build command
  • nix-build example1.nix
  • bind the .drv: low level build recipe (nix-store realise)
  • ls -lah
  • file result
  • cat result
• example2:
  • src
  • default.nix
• example3
  • default is C-style makefile
  • there is unpacking
  • patching
  • configuring
  • building
  • installing
  • and more. read the source
  • there are build inputs
    • build time
    • run time: nix-store -qR result
    • nix figures this out by looks at the build output and scanning for build time dependencies