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c88337c9ac
Docker images used to be, essentially, a linked list of layers. Each
layer would have a tarball and a json document pointing to its parent,
and the image pointed to the top layer:
imageA ----> layerA
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v
layerB
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v
layerC
The current image spec changed this format to where the Image defined
the order and set of layers:
imageA ---> layerA
|--> layerB
`--> layerC
For backwards compatibility, docker produces images which follow both
specs: layers point to parents, and images also point to the entire
list:
imageA ---> layerA
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| v
|--> layerB
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| v
`--> layerC
This is nice for tooling which supported the older version and never
updated to support the newer format.
Our `buildImage` code only supported the old version, so in order for
`buildImage` to properly generate an image based on another image
with `fromImage`, the parent image's layers must fully support the old
mechanism.
This is not a problem in general, but is a problem with
`buildLayeredImage`.
`buildLayeredImage` creates images with newer image spec, because
individual store paths don't have a guaranteed parent layer. Including
a specific parent ID in the layer's json makes the output less likely
to cache hit when published or pulled.
This means until now, `buildLayeredImage` could not be the input to
`buildImage`.
The changes in this PR change `buildImage` to only use the layer's
manifest when locating parent IDs. This does break buildImage on
extremely old Docker images, though I do wonder how many of these
exist.
This work has been sponsored by Target.
180 lines
4.6 KiB
Nix
180 lines
4.6 KiB
Nix
# Examples of using the docker tools to build packages.
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#
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# This file defines several docker images. In order to use an image,
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# build its derivation with `nix-build`, and then load the result with
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# `docker load`. For example:
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#
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# $ nix-build '<nixpkgs>' -A dockerTools.examples.redis
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# $ docker load < result
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{ pkgs, buildImage, pullImage, shadowSetup, buildImageWithNixDb }:
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rec {
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# 1. basic example
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bash = buildImage {
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name = "bash";
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tag = "latest";
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contents = pkgs.bashInteractive;
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};
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# 2. service example, layered on another image
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redis = buildImage {
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name = "redis";
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tag = "latest";
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# for example's sake, we can layer redis on top of bash or debian
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fromImage = bash;
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# fromImage = debian;
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contents = pkgs.redis;
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runAsRoot = ''
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mkdir -p /data
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'';
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config = {
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Cmd = [ "/bin/redis-server" ];
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WorkingDir = "/data";
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Volumes = {
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"/data" = {};
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};
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};
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};
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# 3. another service example
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nginx = let
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nginxPort = "80";
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nginxConf = pkgs.writeText "nginx.conf" ''
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user nginx nginx;
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daemon off;
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error_log /dev/stdout info;
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pid /dev/null;
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events {}
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http {
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access_log /dev/stdout;
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server {
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listen ${nginxPort};
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index index.html;
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location / {
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root ${nginxWebRoot};
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}
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}
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}
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'';
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nginxWebRoot = pkgs.writeTextDir "index.html" ''
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<html><body><h1>Hello from NGINX</h1></body></html>
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'';
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in
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buildImage {
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name = "nginx-container";
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tag = "latest";
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contents = pkgs.nginx;
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runAsRoot = ''
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#!${pkgs.stdenv.shell}
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${shadowSetup}
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groupadd --system nginx
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useradd --system --gid nginx nginx
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'';
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config = {
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Cmd = [ "nginx" "-c" nginxConf ];
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ExposedPorts = {
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"${nginxPort}/tcp" = {};
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};
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};
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};
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# 4. example of pulling an image. could be used as a base for other images
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nixFromDockerHub = pullImage {
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imageName = "nixos/nix";
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imageDigest = "sha256:20d9485b25ecfd89204e843a962c1bd70e9cc6858d65d7f5fadc340246e2116b";
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sha256 = "0mqjy3zq2v6rrhizgb9nvhczl87lcfphq9601wcprdika2jz7qh8";
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finalImageTag = "1.11";
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};
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# 5. example of multiple contents, emacs and vi happily coexisting
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editors = buildImage {
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name = "editors";
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contents = [
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pkgs.coreutils
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pkgs.bash
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pkgs.emacs
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pkgs.vim
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pkgs.nano
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];
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};
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# 6. nix example to play with the container nix store
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# docker run -it --rm nix nix-store -qR $(nix-build '<nixpkgs>' -A nix)
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nix = buildImageWithNixDb {
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name = "nix";
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tag = "latest";
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contents = [
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# nix-store uses cat program to display results as specified by
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# the image env variable NIX_PAGER.
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pkgs.coreutils
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pkgs.nix
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];
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config = {
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Env = [ "NIX_PAGER=cat" ];
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};
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};
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# 7. example of adding something on top of an image pull by our
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# dockerTools chain.
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onTopOfPulledImage = buildImage {
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name = "onTopOfPulledImage";
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tag = "latest";
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fromImage = nixFromDockerHub;
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contents = [ pkgs.hello ];
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};
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# 8. regression test for erroneous use of eval and string expansion.
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# See issue #34779 and PR #40947 for details.
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runAsRootExtraCommands = pkgs.dockerTools.buildImage {
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name = "runAsRootExtraCommands";
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tag = "latest";
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contents = [ pkgs.coreutils ];
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# The parens here are to create problematic bash to embed and eval. In case
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# this is *embedded* into the script (with nix expansion) the initial quotes
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# will close the string and the following parens are unexpected
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runAsRoot = ''echo "(runAsRoot)" > runAsRoot'';
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extraCommands = ''echo "(extraCommand)" > extraCommands'';
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};
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# 9. Ensure that setting created to now results in a date which
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# isn't the epoch + 1
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unstableDate = pkgs.dockerTools.buildImage {
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name = "unstable-date";
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tag = "latest";
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contents = [ pkgs.coreutils ];
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created = "now";
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};
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# 10. Create a layered image
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layered-image = pkgs.dockerTools.buildLayeredImage {
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name = "layered-image";
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tag = "latest";
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config.Cmd = [ "${pkgs.hello}/bin/hello" ];
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contents = [ pkgs.hello pkgs.bash pkgs.coreutils ];
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};
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# 11. Create an image on top of a layered image
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layered-on-top = pkgs.dockerTools.buildImage {
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name = "layered-on-top";
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tag = "latest";
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fromImage = layered-image;
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extraCommands = ''
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mkdir ./example-output
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chmod 777 ./example-output
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'';
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config = {
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Env = [ "PATH=${pkgs.coreutils}/bin/" ];
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WorkingDir = "/example-output";
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Cmd = [
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"${pkgs.bash}/bin/bash" "-c" "echo hello > foo; cat foo"
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];
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};
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};
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}
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