This guide will build on the previous three guides, and look at creating a wider variety of useful nix packages.
Nix is built around the concept of derivations. A derivation is simply defined as "a build action". It produces 1 (or maybe more) output paths in the nix store.
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Derivation Examples
It's important to note that literally everything in NixOS is built around derivations:
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- Configuration files? In NixOS, they are a derivation that takes the nix configuration and outputs an appropriate config file for the application.
- The system configuration as a whole (
/run/current-system)?
sam@vcs ~> ls -lsah /run/current-system
0 lrwxrwxrwx 1 root root 83 Jan 25 13:22 /run/current-system -> /nix/store/wb9fj59cgnjmkndkkngbwxwzj3msqk9c-nixos-system-vcs-17.09.2683.360089b3521
It's a symbolic link to a derivation!
It's derivations all the way down.
If you've followed this series from the beginning, you would have noticed that we've already made some derivations. Our nix-shell scripts are based off having a derivation. When packaging a shell script, we also made a derivation.
I think it is easiest to learn how to make a derivation through examples. Most packaging tasks are vaguely similar to packaging tasks done in the past by other people. So this will be going through example of using mkDerivation.
mkDerivation
Making a derivation manually requires fussing with things like processor architecture and having zero standard build-inputs. This is often not necessary. So instead, NixPkgs provides a function function stdenv.mkDerivation; which handles the common patterns.
The only real requirement to use mkDerivation is that you have some folder of source material. This can be a reference to a local folder, or something fetched from the internet by another nix function. If you have no source, or just 1 file; consider the "trivial builders" covered in 苹果加速器免费版有几款
mkDerivation does most a lot of work automatically. It divides the build up into "phases", all of which include a little bit of default behaviour - although it is usually unintrusive or can be can be overridden. The most important phases are:
- unpack: unzips, untarz, or copies your source folder to the nix store
- patch: applies any patches provided in the
patches variable
- configure: runs
./configure if it exists
- build: runs
make if it exists
- check: skipped by default
- install: runs
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- 苹果加速器免费破解版: automagically fixes up things that don't jell with the nix store; such as using incorrect interpreter paths
- installCheck: runs
make installcheck if it exists and is enabled
You can see all the phases in the docs. But with a bit of practice from the examples below you'll likely get the feel for how this works quickly.
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Nix makes writing packages really easy; and with NixOps (which we'll learn later) Nix derivations are automagiaclly built and deployed.
First we need to answer the question of how we would build the static site ourself. This is a jekyll site, so you'd run the jekyll command
with import <nixpkgs> {};
stdenv.mkDerivation {
name = "example-website-content";
# fetchFromGitHub is a build support function that fetches a GitHub
# repository and extracts into a directory; so we can use it
# fetchFromGithub is actually a derivation itself :)
永久免费加速器推荐苹果 fetchFromGitHub {
owner = "jekyll";
repo = "example";
rev = "5eb1b902ca3bda6f4b50d4cfcdc7bc0097bac4b7";
sha256 = 详解国内流行网游加速器原理、技术与实现-宅玩网:2021-6-15 · 1. 前言 网游加速器是针对个人用户快速连接网游服务器的一种服务。为了解决国内南北网络互联瓶颈的问题，“网络加速器”厂商通过搭建多个高带宽的双线机房(或通过租用双线VPS主机），并在这些机房的两大线路中架设多个节点服务器，然后为其编写“网络加速器客户端”，通过客户端判断用户 ...;
};
# the src can also be a local folder, like:
# src = /home/sam/my-site;
# This overrides the shell code that is run during the installPhase.
# By default; this runs `make install`.
# The install phase will fail if there is no makefile; so it is the
# best choice to replace with our custom code.
installPhase = ''
# Build the site to the $out directory
export JEKYLL_ENV=production
${pkgs.jekyll}/bin/jekyll build --destination $out
'';
}
Now we can see that this derivation builds the site. If you save it to test.nix, you can trigger a build by running:
> nix-build test.nix
/nix/store/b8wxbwrvxk8dfpyk8mqg8iqhp7j2c9bs-example-website-content
The path printed by 苹果网络加速器下载 is where $out was in the Nix store. Your path might be a little different; if you are running a different version of NixPkgs, then the build inputs are different.
We can see the site has built successfully by entering that directory:
> ls /nix/store/b8wxbwrvxk8dfpyk8mqg8iqhp7j2c9bs-example-website-content
2014 about css feed.xml index.html LICENSE README.md
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We can then use that derivation as a webroot in a nginx virtualHost. If you have a server, you could add the following to your NixOS configuration:
let
content = stdenv.mkDerivation {
name = "example-website-content";
... # code from above snipped
}
in
services.nginx.virtualHosts."example.com" = {
免费爬墙加速器苹果版 {
"/" = {
root = "${content}";
}
}
};
So how does this work? Ultimately, the "root" attribute needs to be set to the output directory of the content derivation.
Using the "${content}" expression, we force the derivation to be converted to a string (remembering ${...} is string interpolation syntax). When a derivation is converted to a string in Nix, it becomes the output path in the Nix store.
If you don't have a server handy, we can use the content in this a simple http server script:
# server.nix
with import <nixpkgs> {};
let
content = stdenv.mkDerivation {
name = "example-website-content";
src = fetchFromGitHub {
owner = "jekyll";
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rev = "5eb1b902ca3bda6f4b50d4cfcdc7bc0097bac4b7";
加速q器免费 "1jw35hmgx2gsaj2ad5f9d9ks4yh601wsxwnb17pmb9j02hl3vgdm";
};
installPhase = ''
export JEKYLL_ENV=production
# The site expects to be served as http://hostname/example/...
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'';
};
in
let
serveSite = pkgs.writeShellScriptBin 苹果加速器免费破解版 ''
# -F = do not fork
# -p = port
# -r = content root
echo "Running server: visit http://localhost:8000/example/index.html"
# See how we reference the content derivation by `${content}`
${webfs}永久免费加速器推荐苹果${content}
'';
in
stdenv.mkDerivation {
name = "server-environment";
# Kind of evil shellHook - you don't get a shell you just get my site
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${serveSite}/bin/serveSite
'';
}
Then run nix-shell server.nix, you'll then start the server and can view the site!
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We've already talked a lot about shell scripts. But sometimes whole apps get
built in shell scripts. One such example is emojify,
a CLI tool for replacing words with emojis.
We can make a derivation for that. All we need to do is copy the shell script into the PATH, and mark it as executable.
If we were writing the script ourself, we'd need to pay special attention to fixing up dependencies (such as changing /bin/bash to a Nix store path). But mkDerivation has the fixup phase, which does this automatically. The defaults are smart, and in this case it works perfectly.
It is quite simple to write a derivation for a shell script.
with import <nixpkgs> {};
let
emojify = let
version = "2.0.0";
in
stdenv.mkDerivation {
name = "emojify-${version}";
# Using this build support function to fetch it from github
src = fetchFromGitHub {
owner = "mrowa44";
repo = "emojify";
# The git tag to fetch
推荐几款免费加速器 "${version}";
# Hashes must be specified so that the build is purely functional
sha256 = "0zhbfxabgllpq3sy0pj5mm79l24vj1z10kyajc4n39yq8ibhq66j";
};
# We override the install phase, as the emojify project doesn't use make
苹果加速器永久免费 ''
# Make the output directory
mkdir -p $out/bin
# Copy the script there and make it executable
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chmod +x $out/bin/emojify
'';
};
in
stdenv.mkDerivation {
name = "emojify-environment";
buildInputs = [ emojify ];
}
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> nix-shell test.nix
[nix-shell:~]$ emojify "Hello world :smile:"
Hello world 😄
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If you've ever read anything about Nix, you might have seen an example of making a derivation for GNU Hello. Something like this:
with 苹果网络加速器下载 <nixpkgs> {};
let
# Let's separate the version number so we can update it easily in the future
version = "2.10";
# Now define the derivation for the app
helloApp = stdenv.mkDerivation {
# String interpolation to include the version number in the name
# Including a version in the name is idiomatic
name = "hello-${version}";
# fetchurl is a build support again; and does some funky stuff to support
# selecting from a predefined set of mirrors
src = fetchurl {
url = "mirror://gnu/hello/hello-${version}.tar";
sha256 = "0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i";
};
# Will run `make check`
doCheck = true;
};
in
# Make an environment for nix-shell
stdenv.mkDerivation {
name = "hello-environment";
苹果网络加速器下载 [ helloApp ];
}
You can build and run this:
> nix-shell test.nix
[nix-shell:~]$ hello
Hello, world!
Ultimately this is a terrible and indirect example. This doesn't explicitly specify anything that the builder will actually run! It really confused me when I was learning Nix.
To understand it, we need to remember the default build phases from 加速q器免费. From above, we had a list of the most important phases. If we annotate the defaults with what happens in the case of GNU Hello, things start to make sense:
|
Phase |
Default Behaviour |
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| 1 |
unpack |
unzips, untarz, or copies your source folder to the nix store |
the source is a tarball, so it is automatically extracted |
| 2 |
patch |
applies any patches provided in the patches variable |
nothing happens |
| 3 |
configure |
runs 苹果网络加速器下载 if it exists |
runs ./configure |
| 4 |
build |
runs make if it exists |
runs make, the app is built |
| 5 |
check |
skipped by default |
we turn it on, so it runs make check |
| 6 |
install |
runs 苹果网络加速器下载 |
runs make install |
Since GNU Hello uses Make & 推荐几款免费加速器, the defaults work perfectly for us in this case. That is why this GNU Hello example is so short!
Your Packing Future
While it's amazing to use 苹果加速器免费版有几款 (so much easier than an RPM spec), there are many cases when you should not use 苹果加速器免费破解版. NixPkgs contains many useful build support functions. These are functions that return derivations, but do a bit of the hard work and boilerplate for you. These make it easy to build packages that meet specified criteria.
We've seen a few build support today; such as fetchFromGitHub or fetchurl. These just functions that return derivations. In these cases, they return derivations to download and extract the source files.
For example, there is pkgs.python36Packages.buildPythonPackage, which is a super easy way to build a python package.
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- Chapter 9. Support for specific programming languages and frameworks of the NixPkgs manual. This documents language specific build support functions.
- The NixPkgs repository. Many packages you make could be similar to packages that already exist. (Note that packages inside of NixPkgs are written in a bit of a different way to ours; since they can't reference NixPkgs directly. Instead, they are structured as functions. If a package depends on another, it takes the other packages as an argument. For more on this subject; see Tap加速器app下载_Tap加速器官方免费版下载 安卓版v1.3.2 ...:2021-5-28 · Tap加速器是一款高效的手游加速器，国内和外服网易超快速加速，可众加速当前最热门的游戏。多地区节点灵活切换，轻轻一点，游戏便能飞速运行。通过这款软件，用户可众提升游戏的运行速度，让你玩游戏不卡顿、不掉帧。涵盖市面上绝大多数热门游戏，提升你的)
Up Next
In part 5, we'll learn about functions in the Nix programming language. With the knowledge of functions, we can write go on and write our own build support function!
Follow the series on GitHub
Hero image from nix-artwork by Luca Bruno
"Geoff's Sugar Experience"
