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Initial commit of additional slides
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‎default.nix

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# default parameter, lazily imports all of nixpkgs namespace into scope
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{ pkgs ? import <nixpkgs> {} }:
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# stdenv is passed in automatically
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pkgs.stdenv.mkDerivation rec {
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name = "hello-2.9";
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# src itself is a derivation, all derivations are stored in the /nix/store, before being realized
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src = pkgs.fetchurl {
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# URL of source to fetch
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url = "mirror://gnu/hello/${name}.tar.gz";
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# Hash of source
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sha256 = "19qy37gkasc4csb1d3bdiz9snn8mir2p3aj0jgzmfv0r2hi7mfzc";
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};
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# cheat to see how build phases run
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preBuild = ''
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set -x
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'';
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}

‎nixtalk.org

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#+REVEAL_THEME: night
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#+OPTIONS: toc:nil num:nil
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#+TITLE: Nix Introduction
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#+AUTHOR: David Johnson & Kevin Quick
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#+AUTHOR: Kevin Quick & David Johnson
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* Sales Pitch
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* Why use nix to install packages?
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* Reproducible builds
@@ -76,90 +76,90 @@
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* Roadmap
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#+ATTR_REVEAL: :frag (none highlight-green highlight-green none none)
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1. Define a pure language
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2. Evaluate language to determine goals
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3. Effect goals in IO
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2. Create Derivations
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3. Realize Derivations
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4. Store results
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5. Compose results into environments
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* nix effects (aka. IO)
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* core set of builders (aka. "stdenv")
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[[https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh][https://github.com/NixOS/nixpkgs/blob/master]]
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[[https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh][/pkgs/stdenv/generic/setup.sh]]
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* look for specific attributes and use them
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* builders
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* look for specific attributes
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* can define stages
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* invoke sub-builders
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* build specification
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* Determine build goal
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* Create Derivations
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* What is a Derivation?
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* A derivation is the instructions on how to build something, and references to every dependency it has.
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* Derivations are implemented as sets, but treated specially during evaluation.
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- Perform side effects like producing build output
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* derivation is the most important primitive in nix
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- Requires a name
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- Requires a builder (script for building the package)
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- All attributes are passed as environment variables to the build.
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- Requires a src (can use local source, or perform IO and fetch over network)
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* In practice you'll use wrappers (i.e. runCommand, writeScriptBin, mkDerivation).
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* mkDerivation uses setup.sh by default
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- [[https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh][https://github.com/ixOS/nixpkgs/blob/master]][[https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh][/pkgs/stdenv/generic/setup.sh]]
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* fetchUrl, fetchFromGitHub, fetchFromGitLab, etc. are fixed output derivations.
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- Perform network IO, but "pure" because they perform "hash matching".
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* Sample derivation
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#+BEGIN_EXAMPLE
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$ nix-env -iA nix.pkgs.git
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#+END_EXAMPLE
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* Specifies the derivation to run the builder on
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#+BEGIN_SRC nix
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nix = { ...
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pkgs = { ...
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git = mkDerivation { name="git"; src=...; ...}
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...
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};
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# default parameter, lazily imports all of nixpkgs namespace into scope
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{ pkgs ? import <nixpkgs> {} }:
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# stdenv is passed in automatically
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pkgs.stdenv.mkDerivation {
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# name
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name = "hello-2.9";
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# src itself is a derivation
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# All derivations are stored in the /nix/store, before being realized
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src = pkgs.fetchurl {
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url = "mirror://gnu/hello/${name}.tar.gz";
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sha256 = "19qy37gkasc4csb1d3bdiz9snn8mir2p3aj0jgzmfv0r2hi7mfzc";
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};
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}
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#+END_SRC
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* Here "nix" is actually a "channel" name (described later)
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* Roadmap
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#+ATTR_REVEAL: :frag (none none none highlight-green none)
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1. Define a pure language
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2. Evaluate language to determine goals
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3. Effect goals in IO
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4. Store results
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5. Compose results into environments
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* nix-env command
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* Input is which derivation to run builders on
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* nix-env puts build output into the "store"
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#+END_EXAMPLE
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* nix store
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* Building a derivation puts build output into the "store"
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- System global directory tree
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* Nothing is in scope
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- dependencies passed in to derivation as args
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- args reference store locations
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- nix-env recursively builds dependencies
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** Unique hashes
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* each store entry identified by hash
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#+BEGIN_EXAMPLE
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$ ls -CF /nix/store/q0crs4bg5vgl9cjpp9yxysd1w97inr0-git-2.13.2/
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bin/ etc/ lib/ libexec/ share/
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bin/ etc/ lib/ libexec/ share/
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#+END_EXAMPLE
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** Unique hashes
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* every package and every version has unique hash
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* closure over build-time inputs
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#+BEGIN_EXAMPLE
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$ ls /nix/store/<TAB>
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Display all 7644 possibilities? (y or n)
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#+END_EXAMPLE
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* can have multiple versions
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* each store location is isolated
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* all dependencies are _explicit_ in the derivation
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** Sample specification
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#+BEGIN_SRC nix
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{ stdenv, fetchurl, pkgconfig, libgphoto2, libexif, popt, gettext
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, libjpeg, readline, libtool
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}:
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stdenv.mkDerivation rec {
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name = "gphoto2-2.5.11";
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src = fetchurl {
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url = "mirror://sourceforge/gphoto/${name}.tar.bz2";
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sha256 = "1sgr6rsvzzagcwhc8fxbnvz3k02wr2hab0vrbvcb04k5l3b48a1r";
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};
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nativeBuildInputs = [ pkgconfig gettext libtool ];
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buildInputs = [ libgphoto2 libexif popt libjpeg readline ];
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meta = with stdenv.lib; {
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description = "A ready to use set of digital camera software applications";
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homepage = http://www.gphoto.org/;
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license = licenses.gpl2Plus;
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platforms = platforms.unix;
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maintainers = [ maintainers.jcumming ];
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};
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}
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#+END_SRC
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* Realize derivations
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* Phase distinction, instantiation & realization
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* nix (https://github.com/nixos/nix)
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- Heart of nix system, 4 C++ libraries, dozen or so utilities
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* nix-instantiate
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- Creates build instructions, calculates hash
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- https://gist.github.com/dmjio/7e5a024f95fe18aa34f8fea69ecebc74#file-derivation-txt-L2
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- https://github.com/NixOS/nix/blob/master/src/libstore/store-api.cc#L104
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- Will exploit binary cache if store path exists on networked machines
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* nix-store -r
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- Attempts to build ("realize") package from derivation description
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- Can watch evaluation through setup.sh by tracing "set -x"
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* nix-build
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- Equivalent to calling 'nix-store -r $(nix-instantiate default.nix)'
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- Creates derivation, builds package, installs in store
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* Builds go through phases
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- pre/postFetch, pre/postBuild, pre/postInstall. etc/
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- Package builds are split into phases to make it easier to override specific parts of the build (e.g., unpacking the sources or installing the binaries).
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- New phases can be defined (haskell packages does this, i.e. haddockPhase)
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- Default phase behavior can be seen in setup.sh
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* nix-shell $(nix-instantiate default.nix)
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- Useful for interactively building derivations
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- Puts a user into a shell with environment variables from the derivation present
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- Can run the build with `genericBuild`
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* Roadmap
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#+ATTR_REVEAL: :frag (none none none highlight-green none)
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1. Define a pure language
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2. Evaluate language to determine goals
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3. Effect goals in IO
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4. Store results
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5. Compose results into environments
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* Roadmap
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#+ATTR_REVEAL: :frag (none none none none highlight-green)
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1. Define a pure language
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- nix-shell
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- shell with build environment, but doesn't build current
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package
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* nix pkgs
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* nixpkgs
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* A large set of ready-made derivations
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* Each function is (ultimately) the mkDerivation
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* channels: tarball of packages
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https://github.com/Gabriel439/haskell-nix
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* Also John Wiegley's work:
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https://github.com/jwiegley/nix-config
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** Sample specification
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#+BEGIN_SRC nix
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{ stdenv, fetchurl, pkgconfig, libgphoto2, libexif, popt, gettext
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, libjpeg, readline, libtool
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}:
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stdenv.mkDerivation rec {
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name = "gphoto2-2.5.11";
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src = fetchurl {
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url = "mirror://sourceforge/gphoto/${name}.tar.bz2";
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sha256 = "1sgr6rsvzzagcwhc8fxbnvz3k02wr2hab0vrbvcb04k5l3b48a1r";
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};
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nativeBuildInputs = [ pkgconfig gettext libtool ];
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buildInputs = [ libgphoto2 libexif popt libjpeg readline ];
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meta = with stdenv.lib; {
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description = "A ready to use set of digital camera software applications";
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homepage = http://www.gphoto.org/;
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license = licenses.gpl2Plus;
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platforms = platforms.unix;
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maintainers = [ maintainers.jcumming ];
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};
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}
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#+END_SRC
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* REPL
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* REPL tool for language and inspection
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#+BEGIN_EXAMPLE
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- Filesystem dirent refcnts determine when removeable.
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* Prefer nix-shell to nix-env
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- Keep your main environment minimal
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* Examples
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- CyberChaff
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- Build
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- https://gist.github.com/e6ad693c41b49b925557fd52aaaf6a42
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- DDOS-gui (http://ddos.dmj.io)
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- Build
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- https://gist.github.com/dmjio/3a1d977fe9e537ca2ad6efcd3a708d4b
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- NixOS module, deployment
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- https://gist.github.com/dmjio/7c0cb81113c7c46cf35edceb5c7960ac
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- https://gist.github.com/dmjio/7705f8c112506f8e93ee09271ccdd14e
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* THE END
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* Nix language
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- https://nixos.org/nix/manual

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