mirror of
https://github.com/NixOS/nixpkgs.git
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dadc7eb329
Whenever we create scripts that are installed to $out, we must use runtimeShell in order to get the shell that can be executed on the machine we create the package for. This is relevant for cross-compiling. The only use case for stdenv.shell are scripts that are executed as part of the build system. Usages in checkPhase are borderline however to decrease the likelyhood of people copying the wrong examples, I decided to use runtimeShell as well.
564 lines
18 KiB
XML
564 lines
18 KiB
XML
<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xml:id="sec-pkgs-dockerTools">
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<title>pkgs.dockerTools</title>
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<para>
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<varname>pkgs.dockerTools</varname> is a set of functions for creating and
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manipulating Docker images according to the
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<link xlink:href="https://github.com/moby/moby/blob/master/image/spec/v1.2.md#docker-image-specification-v120">
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Docker Image Specification v1.2.0 </link>. Docker itself is not used to
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perform any of the operations done by these functions.
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</para>
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<warning>
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<para>
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The <varname>dockerTools</varname> API is unstable and may be subject to
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backwards-incompatible changes in the future.
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</para>
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</warning>
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<section xml:id="ssec-pkgs-dockerTools-buildImage">
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<title>buildImage</title>
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<para>
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This function is analogous to the <command>docker build</command> command,
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in that it can be used to build a Docker-compatible repository tarball containing
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a single image with one or multiple layers. As such, the result is suitable
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for being loaded in Docker with <command>docker load</command>.
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</para>
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<para>
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The parameters of <varname>buildImage</varname> with relative example values
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are described below:
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</para>
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<example xml:id='ex-dockerTools-buildImage'>
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<title>Docker build</title>
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<programlisting>
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buildImage {
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name = "redis"; <co xml:id='ex-dockerTools-buildImage-1' />
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tag = "latest"; <co xml:id='ex-dockerTools-buildImage-2' />
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fromImage = someBaseImage; <co xml:id='ex-dockerTools-buildImage-3' />
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fromImageName = null; <co xml:id='ex-dockerTools-buildImage-4' />
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fromImageTag = "latest"; <co xml:id='ex-dockerTools-buildImage-5' />
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contents = pkgs.redis; <co xml:id='ex-dockerTools-buildImage-6' />
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runAsRoot = '' <co xml:id='ex-dockerTools-buildImage-runAsRoot' />
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#!${pkgs.runtimeShell}
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mkdir -p /data
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'';
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config = { <co xml:id='ex-dockerTools-buildImage-8' />
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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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</programlisting>
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</example>
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<para>
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The above example will build a Docker image <literal>redis/latest</literal>
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from the given base image. Loading and running this image in Docker results
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in <literal>redis-server</literal> being started automatically.
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</para>
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<calloutlist>
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<callout arearefs='ex-dockerTools-buildImage-1'>
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<para>
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<varname>name</varname> specifies the name of the resulting image. This is
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the only required argument for <varname>buildImage</varname>.
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</para>
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</callout>
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<callout arearefs='ex-dockerTools-buildImage-2'>
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<para>
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<varname>tag</varname> specifies the tag of the resulting image. By
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default it's <literal>null</literal>, which indicates that the nix output
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hash will be used as tag.
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</para>
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</callout>
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<callout arearefs='ex-dockerTools-buildImage-3'>
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<para>
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<varname>fromImage</varname> is the repository tarball containing the base
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image. It must be a valid Docker image, such as exported by
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<command>docker save</command>. By default it's <literal>null</literal>,
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which can be seen as equivalent to <literal>FROM scratch</literal> of a
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<filename>Dockerfile</filename>.
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</para>
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</callout>
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<callout arearefs='ex-dockerTools-buildImage-4'>
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<para>
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<varname>fromImageName</varname> can be used to further specify the base
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image within the repository, in case it contains multiple images. By
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default it's <literal>null</literal>, in which case
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<varname>buildImage</varname> will peek the first image available in the
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repository.
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</para>
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</callout>
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<callout arearefs='ex-dockerTools-buildImage-5'>
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<para>
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<varname>fromImageTag</varname> can be used to further specify the tag of
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the base image within the repository, in case an image contains multiple
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tags. By default it's <literal>null</literal>, in which case
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<varname>buildImage</varname> will peek the first tag available for the
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base image.
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</para>
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</callout>
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<callout arearefs='ex-dockerTools-buildImage-6'>
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<para>
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<varname>contents</varname> is a derivation that will be copied in the new
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layer of the resulting image. This can be similarly seen as <command>ADD
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contents/ /</command> in a <filename>Dockerfile</filename>. By default
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it's <literal>null</literal>.
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</para>
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</callout>
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<callout arearefs='ex-dockerTools-buildImage-runAsRoot'>
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<para>
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<varname>runAsRoot</varname> is a bash script that will run as root in an
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environment that overlays the existing layers of the base image with the
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new resulting layer, including the previously copied
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<varname>contents</varname> derivation. This can be similarly seen as
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<command>RUN ...</command> in a <filename>Dockerfile</filename>.
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<note>
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<para>
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Using this parameter requires the <literal>kvm</literal> device to be
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available.
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</para>
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</note>
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</para>
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</callout>
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<callout arearefs='ex-dockerTools-buildImage-8'>
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<para>
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<varname>config</varname> is used to specify the configuration of the
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containers that will be started off the built image in Docker. The
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available options are listed in the
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<link xlink:href="https://github.com/moby/moby/blob/master/image/spec/v1.2.md#image-json-field-descriptions">
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Docker Image Specification v1.2.0 </link>.
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</para>
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</callout>
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</calloutlist>
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<para>
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After the new layer has been created, its closure (to which
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<varname>contents</varname>, <varname>config</varname> and
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<varname>runAsRoot</varname> contribute) will be copied in the layer itself.
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Only new dependencies that are not already in the existing layers will be
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copied.
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</para>
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<para>
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At the end of the process, only one new single layer will be produced and
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added to the resulting image.
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</para>
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<para>
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The resulting repository will only list the single image
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<varname>image/tag</varname>. In the case of
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<xref linkend='ex-dockerTools-buildImage'/> it would be
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<varname>redis/latest</varname>.
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</para>
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<para>
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It is possible to inspect the arguments with which an image was built using
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its <varname>buildArgs</varname> attribute.
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</para>
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<note>
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<para>
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If you see errors similar to <literal>getProtocolByName: does not exist (no
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such protocol name: tcp)</literal> you may need to add
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<literal>pkgs.iana-etc</literal> to <varname>contents</varname>.
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</para>
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</note>
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<note>
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<para>
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If you see errors similar to <literal>Error_Protocol ("certificate has
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unknown CA",True,UnknownCa)</literal> you may need to add
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<literal>pkgs.cacert</literal> to <varname>contents</varname>.
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</para>
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</note>
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<example xml:id="example-pkgs-dockerTools-buildImage-creation-date">
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<title>Impurely Defining a Docker Layer's Creation Date</title>
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<para>
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By default <function>buildImage</function> will use a static date of one
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second past the UNIX Epoch. This allows <function>buildImage</function> to
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produce binary reproducible images. When listing images with
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<command>docker images</command>, the newly created images will be
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listed like this:
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</para>
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<screen><![CDATA[
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$ docker images
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REPOSITORY TAG IMAGE ID CREATED SIZE
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hello latest 08c791c7846e 48 years ago 25.2MB
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]]></screen>
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<para>
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You can break binary reproducibility but have a sorted, meaningful
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<literal>CREATED</literal> column by setting <literal>created</literal> to
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<literal>now</literal>.
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</para>
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<programlisting><![CDATA[
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pkgs.dockerTools.buildImage {
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name = "hello";
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tag = "latest";
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created = "now";
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contents = pkgs.hello;
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config.Cmd = [ "/bin/hello" ];
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}
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]]></programlisting>
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<para>
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and now the Docker CLI will display a reasonable date and sort the images
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as expected:
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<screen><![CDATA[
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$ docker images
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REPOSITORY TAG IMAGE ID CREATED SIZE
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hello latest de2bf4786de6 About a minute ago 25.2MB
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]]></screen>
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however, the produced images will not be binary reproducible.
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</para>
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</example>
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</section>
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<section xml:id="ssec-pkgs-dockerTools-buildLayeredImage">
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<title>buildLayeredImage</title>
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<para>
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Create a Docker image with many of the store paths being on their own layer
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to improve sharing between images.
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</para>
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<variablelist>
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<varlistentry>
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<term>
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<varname>name</varname>
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</term>
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<listitem>
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<para>
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The name of the resulting image.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<varname>tag</varname> <emphasis>optional</emphasis>
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</term>
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<listitem>
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<para>
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Tag of the generated image.
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</para>
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<para>
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<emphasis>Default:</emphasis> the output path's hash
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<varname>contents</varname> <emphasis>optional</emphasis>
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</term>
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<listitem>
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<para>
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Top level paths in the container. Either a single derivation, or a list
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of derivations.
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</para>
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<para>
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<emphasis>Default:</emphasis> <literal>[]</literal>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<varname>config</varname> <emphasis>optional</emphasis>
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</term>
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<listitem>
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<para>
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Run-time configuration of the container. A full list of the options are
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available at in the
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<link xlink:href="https://github.com/moby/moby/blob/master/image/spec/v1.2.md#image-json-field-descriptions">
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Docker Image Specification v1.2.0 </link>.
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</para>
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<para>
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<emphasis>Default:</emphasis> <literal>{}</literal>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<varname>created</varname> <emphasis>optional</emphasis>
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</term>
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<listitem>
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<para>
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Date and time the layers were created. Follows the same
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<literal>now</literal> exception supported by
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<literal>buildImage</literal>.
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</para>
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<para>
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<emphasis>Default:</emphasis> <literal>1970-01-01T00:00:01Z</literal>
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>
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<varname>maxLayers</varname> <emphasis>optional</emphasis>
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</term>
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<listitem>
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<para>
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Maximum number of layers to create.
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</para>
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<para>
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<emphasis>Default:</emphasis> <literal>24</literal>
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<section xml:id="dockerTools-buildLayeredImage-arg-contents">
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<title>Behavior of <varname>contents</varname> in the final image</title>
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<para>
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Each path directly listed in <varname>contents</varname> will have a
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symlink in the root of the image.
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</para>
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<para>
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For example:
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<programlisting><![CDATA[
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pkgs.dockerTools.buildLayeredImage {
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name = "hello";
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contents = [ pkgs.hello ];
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}
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]]></programlisting>
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will create symlinks for all the paths in the <literal>hello</literal>
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package:
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<screen><![CDATA[
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/bin/hello -> /nix/store/h1zb1padqbbb7jicsvkmrym3r6snphxg-hello-2.10/bin/hello
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/share/info/hello.info -> /nix/store/h1zb1padqbbb7jicsvkmrym3r6snphxg-hello-2.10/share/info/hello.info
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/share/locale/bg/LC_MESSAGES/hello.mo -> /nix/store/h1zb1padqbbb7jicsvkmrym3r6snphxg-hello-2.10/share/locale/bg/LC_MESSAGES/hello.mo
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]]></screen>
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</para>
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</section>
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<section xml:id="dockerTools-buildLayeredImage-arg-config">
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<title>Automatic inclusion of <varname>config</varname> references</title>
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<para>
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The closure of <varname>config</varname> is automatically included in the
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closure of the final image.
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</para>
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<para>
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This allows you to make very simple Docker images with very little code.
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This container will start up and run <command>hello</command>:
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<programlisting><![CDATA[
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pkgs.dockerTools.buildLayeredImage {
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name = "hello";
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config.Cmd = [ "${pkgs.hello}/bin/hello" ];
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}
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]]></programlisting>
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</para>
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</section>
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<section xml:id="dockerTools-buildLayeredImage-arg-maxLayers">
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<title>Adjusting <varname>maxLayers</varname></title>
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<para>
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Increasing the <varname>maxLayers</varname> increases the number of layers
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which have a chance to be shared between different images.
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</para>
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<para>
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Modern Docker installations support up to 128 layers, however older
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versions support as few as 42.
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</para>
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<para>
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If the produced image will not be extended by other Docker builds, it is
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safe to set <varname>maxLayers</varname> to <literal>128</literal>. However
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it will be impossible to extend the image further.
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</para>
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<para>
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The first (<literal>maxLayers-2</literal>) most "popular" paths will have
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their own individual layers, then layer #<literal>maxLayers-1</literal>
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will contain all the remaining "unpopular" paths, and finally layer
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#<literal>maxLayers</literal> will contain the Image configuration.
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</para>
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<para>
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Docker's Layers are not inherently ordered, they are content-addressable
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and are not explicitly layered until they are composed in to an Image.
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</para>
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</section>
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</section>
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<section xml:id="ssec-pkgs-dockerTools-fetchFromRegistry">
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<title>pullImage</title>
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<para>
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This function is analogous to the <command>docker pull</command> command, in
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that it can be used to pull a Docker image from a Docker registry. By default
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<link xlink:href="https://hub.docker.com/">Docker Hub</link> is used to pull
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images.
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</para>
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<para>
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Its parameters are described in the example below:
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</para>
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<example xml:id='ex-dockerTools-pullImage'>
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<title>Docker pull</title>
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<programlisting>
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pullImage {
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imageName = "nixos/nix"; <co xml:id='ex-dockerTools-pullImage-1' />
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imageDigest = "sha256:20d9485b25ecfd89204e843a962c1bd70e9cc6858d65d7f5fadc340246e2116b"; <co xml:id='ex-dockerTools-pullImage-2' />
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finalImageTag = "1.11"; <co xml:id='ex-dockerTools-pullImage-3' />
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sha256 = "0mqjy3zq2v6rrhizgb9nvhczl87lcfphq9601wcprdika2jz7qh8"; <co xml:id='ex-dockerTools-pullImage-4' />
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os = "linux"; <co xml:id='ex-dockerTools-pullImage-5' />
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arch = "x86_64"; <co xml:id='ex-dockerTools-pullImage-6' />
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}
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</programlisting>
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</example>
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<calloutlist>
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<callout arearefs='ex-dockerTools-pullImage-1'>
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<para>
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<varname>imageName</varname> specifies the name of the image to be
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downloaded, which can also include the registry namespace (e.g.
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<literal>nixos</literal>). This argument is required.
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</para>
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</callout>
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<callout arearefs='ex-dockerTools-pullImage-2'>
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<para>
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<varname>imageDigest</varname> specifies the digest of the image to be
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downloaded. Skopeo can be used to get the digest of an image, with its
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<varname>inspect</varname> subcommand. Since a given
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<varname>imageName</varname> may transparently refer to a manifest list of
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images which support multiple architectures and/or operating systems,
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supply the `--override-os` and `--override-arch` arguments to specify
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exactly which image you want. By default it will match the OS and
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architecture of the host the command is run on.
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<programlisting>
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$ nix-shell --packages skopeo jq --command "skopeo --override-os linux --override-arch x86_64 inspect docker://docker.io/nixos/nix:1.11 | jq -r '.Digest'"
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sha256:20d9485b25ecfd89204e843a962c1bd70e9cc6858d65d7f5fadc340246e2116b
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</programlisting>
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This argument is required.
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</para>
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</callout>
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<callout arearefs='ex-dockerTools-pullImage-3'>
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<para>
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<varname>finalImageTag</varname>, if specified, this is the tag of the
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image to be created. Note it is never used to fetch the image since we
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prefer to rely on the immutable digest ID. By default it's
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<literal>latest</literal>.
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</para>
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</callout>
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<callout arearefs='ex-dockerTools-pullImage-4'>
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<para>
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<varname>sha256</varname> is the checksum of the whole fetched image. This
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argument is required.
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</para>
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</callout>
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<callout arearefs='ex-dockerTools-pullImage-5'>
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<para>
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<varname>os</varname>, if specified, is the operating system of the
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fetched image. By default it's <literal>linux</literal>.
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|
</para>
|
|
</callout>
|
|
<callout arearefs='ex-dockerTools-pullImage-6'>
|
|
<para>
|
|
<varname>arch</varname>, if specified, is the cpu architecture of the
|
|
fetched image. By default it's <literal>x86_64</literal>.
|
|
</para>
|
|
</callout>
|
|
</calloutlist>
|
|
</section>
|
|
|
|
<section xml:id="ssec-pkgs-dockerTools-exportImage">
|
|
<title>exportImage</title>
|
|
|
|
<para>
|
|
This function is analogous to the <command>docker export</command> command,
|
|
in that it can be used to flatten a Docker image that contains multiple layers. It
|
|
is in fact the result of the merge of all the layers of the image. As such,
|
|
the result is suitable for being imported in Docker with <command>docker
|
|
import</command>.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
Using this function requires the <literal>kvm</literal> device to be
|
|
available.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
The parameters of <varname>exportImage</varname> are the following:
|
|
</para>
|
|
|
|
<example xml:id='ex-dockerTools-exportImage'>
|
|
<title>Docker export</title>
|
|
<programlisting>
|
|
exportImage {
|
|
fromImage = someLayeredImage;
|
|
fromImageName = null;
|
|
fromImageTag = null;
|
|
|
|
name = someLayeredImage.name;
|
|
}
|
|
</programlisting>
|
|
</example>
|
|
|
|
<para>
|
|
The parameters relative to the base image have the same synopsis as
|
|
described in <xref linkend='ssec-pkgs-dockerTools-buildImage'/>, except that
|
|
<varname>fromImage</varname> is the only required argument in this case.
|
|
</para>
|
|
|
|
<para>
|
|
The <varname>name</varname> argument is the name of the derivation output,
|
|
which defaults to <varname>fromImage.name</varname>.
|
|
</para>
|
|
</section>
|
|
|
|
<section xml:id="ssec-pkgs-dockerTools-shadowSetup">
|
|
<title>shadowSetup</title>
|
|
|
|
<para>
|
|
This constant string is a helper for setting up the base files for managing
|
|
users and groups, only if such files don't exist already. It is suitable for
|
|
being used in a <varname>runAsRoot</varname>
|
|
<xref linkend='ex-dockerTools-buildImage-runAsRoot'/> script for cases like
|
|
in the example below:
|
|
</para>
|
|
|
|
<example xml:id='ex-dockerTools-shadowSetup'>
|
|
<title>Shadow base files</title>
|
|
<programlisting>
|
|
buildImage {
|
|
name = "shadow-basic";
|
|
|
|
runAsRoot = ''
|
|
#!${pkgs.runtimeShell}
|
|
${shadowSetup}
|
|
groupadd -r redis
|
|
useradd -r -g redis redis
|
|
mkdir /data
|
|
chown redis:redis /data
|
|
'';
|
|
}
|
|
</programlisting>
|
|
</example>
|
|
|
|
<para>
|
|
Creating base files like <literal>/etc/passwd</literal> or
|
|
<literal>/etc/login.defs</literal> is necessary for shadow-utils to
|
|
manipulate users and groups.
|
|
</para>
|
|
</section>
|
|
</section>
|