nixpkgs/pkgs/build-support/docker/examples.nix
Antoine Eiche 736848723e dockerTools.pullImage: Skopeo pulls images by digest
Skopeo is used to pull images from a Docker registry (instead of a
Docker deamon in a VM).

An image reference is specified with its name and its digest which is
an immutable image identifier (unlike image name and tag).

Skopeo can be used to get the digest of an image, for instance:
$ skopeo inspect docker://docker.io/nixos/nix:1.11 | jq -r '.Digest'
2018-05-02 21:32:20 +02:00

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Nix

# Examples of using the docker tools to build packages.
#
# This file defines several docker images. In order to use an image,
# build its derivation with `nix-build`, and then load the result with
# `docker load`. For example:
#
# $ nix-build '<nixpkgs>' -A dockerTools.examples.redis
# $ docker load < result
{ pkgs, buildImage, pullImage, shadowSetup, buildImageWithNixDb }:
rec {
# 1. basic example
bash = buildImage {
name = "bash";
contents = pkgs.bashInteractive;
};
# 2. service example, layered on another image
redis = buildImage {
name = "redis";
tag = "latest";
# for example's sake, we can layer redis on top of bash or debian
fromImage = bash;
# fromImage = debian;
contents = pkgs.redis;
runAsRoot = ''
mkdir -p /data
'';
config = {
Cmd = [ "/bin/redis-server" ];
WorkingDir = "/data";
Volumes = {
"/data" = {};
};
};
};
# 3. another service example
nginx = let
nginxPort = "80";
nginxConf = pkgs.writeText "nginx.conf" ''
user nginx nginx;
daemon off;
error_log /dev/stdout info;
pid /dev/null;
events {}
http {
access_log /dev/stdout;
server {
listen ${nginxPort};
index index.html;
location / {
root ${nginxWebRoot};
}
}
}
'';
nginxWebRoot = pkgs.writeTextDir "index.html" ''
<html><body><h1>Hello from NGINX</h1></body></html>
'';
in
buildImage {
name = "nginx-container";
contents = pkgs.nginx;
runAsRoot = ''
#!${pkgs.stdenv.shell}
${shadowSetup}
groupadd --system nginx
useradd --system --gid nginx nginx
'';
config = {
Cmd = [ "nginx" "-c" nginxConf ];
ExposedPorts = {
"${nginxPort}/tcp" = {};
};
};
};
# 4. example of pulling an image. could be used as a base for other images
nixFromDockerHub = pullImage {
imageName = "nixos/nix";
imageDigest = "sha256:20d9485b25ecfd89204e843a962c1bd70e9cc6858d65d7f5fadc340246e2116b";
sha256 = "0mqjy3zq2v6rrhizgb9nvhczl87lcfphq9601wcprdika2jz7qh8";
finalImageTag = "1.11";
};
# 5. example of multiple contents, emacs and vi happily coexisting
editors = buildImage {
name = "editors";
contents = [
pkgs.coreutils
pkgs.bash
pkgs.emacs
pkgs.vim
pkgs.nano
];
};
# 6. nix example to play with the container nix store
# docker run -it --rm nix nix-store -qR $(nix-build '<nixpkgs>' -A nix)
nix = buildImageWithNixDb {
name = "nix";
contents = [
# nix-store uses cat program to display results as specified by
# the image env variable NIX_PAGER.
pkgs.coreutils
pkgs.nix
];
config = {
Env = [ "NIX_PAGER=cat" ];
};
};
# 7. example of adding something on top of an image pull by our
# dockerTools chain.
onTopOfPulledImage = buildImage {
name = "onTopOfPulledImage";
fromImage = nixFromDockerHub;
contents = [ pkgs.hello ];
};
}