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diff --git a/doc/functions.xml b/doc/functions.xml index 8223a8b0531c..88011061ae6e 100644 --- a/doc/functions.xml +++ b/doc/functions.xml @@ -7,1016 +7,11 @@ The nixpkgs repository has several utility functions to manipulate Nix expressions. </para> - <section xml:id="sec-overrides"> - <title>Overriding</title> - <para> - Sometimes one wants to override parts of <literal>nixpkgs</literal>, e.g. - derivation attributes, the results of derivations or even the whole package - set. - </para> - - <section xml:id="sec-pkg-override"> - <title><pkg>.override</title> - - <para> - The function <varname>override</varname> is usually available for all the - derivations in the nixpkgs expression (<varname>pkgs</varname>). - </para> - - <para> - It is used to override the arguments passed to a function. - </para> - - <para> - Example usages: -<programlisting>pkgs.foo.override { arg1 = val1; arg2 = val2; ... }</programlisting> -<programlisting> -import pkgs.path { overlays = [ (self: super: { - foo = super.foo.override { barSupport = true ; }; - })]}; -</programlisting> -<programlisting> -mypkg = pkgs.callPackage ./mypkg.nix { - mydep = pkgs.mydep.override { ... }; - } -</programlisting> - </para> - - <para> - In the first example, <varname>pkgs.foo</varname> is the result of a - function call with some default arguments, usually a derivation. Using - <varname>pkgs.foo.override</varname> will call the same function with the - given new arguments. - </para> - </section> - - <section xml:id="sec-pkg-overrideAttrs"> - <title><pkg>.overrideAttrs</title> - - <para> - The function <varname>overrideAttrs</varname> allows overriding the - attribute set passed to a <varname>stdenv.mkDerivation</varname> call, - producing a new derivation based on the original one. This function is - available on all derivations produced by the - <varname>stdenv.mkDerivation</varname> function, which is most packages in - the nixpkgs expression <varname>pkgs</varname>. - </para> - - <para> - Example usage: -<programlisting> -helloWithDebug = pkgs.hello.overrideAttrs (oldAttrs: rec { - separateDebugInfo = true; -}); -</programlisting> - </para> - - <para> - In the above example, the <varname>separateDebugInfo</varname> attribute is - overridden to be true, thus building debug info for - <varname>helloWithDebug</varname>, while all other attributes will be - retained from the original <varname>hello</varname> package. - </para> - - <para> - The argument <varname>oldAttrs</varname> is conventionally used to refer to - the attr set originally passed to <varname>stdenv.mkDerivation</varname>. - </para> - - <note> - <para> - Note that <varname>separateDebugInfo</varname> is processed only by the - <varname>stdenv.mkDerivation</varname> function, not the generated, raw - Nix derivation. Thus, using <varname>overrideDerivation</varname> will not - work in this case, as it overrides only the attributes of the final - derivation. It is for this reason that <varname>overrideAttrs</varname> - should be preferred in (almost) all cases to - <varname>overrideDerivation</varname>, i.e. to allow using - <varname>sdenv.mkDerivation</varname> to process input arguments, as well - as the fact that it is easier to use (you can use the same attribute names - you see in your Nix code, instead of the ones generated (e.g. - <varname>buildInputs</varname> vs <varname>nativeBuildInputs</varname>, - and involves less typing. - </para> - </note> - </section> - - <section xml:id="sec-pkg-overrideDerivation"> - <title><pkg>.overrideDerivation</title> - - <warning> - <para> - You should prefer <varname>overrideAttrs</varname> in almost all cases, - see its documentation for the reasons why. - <varname>overrideDerivation</varname> is not deprecated and will continue - to work, but is less nice to use and does not have as many abilities as - <varname>overrideAttrs</varname>. - </para> - </warning> - - <warning> - <para> - Do not use this function in Nixpkgs as it evaluates a Derivation before - modifying it, which breaks package abstraction and removes error-checking - of function arguments. In addition, this evaluation-per-function - application incurs a performance penalty, which can become a problem if - many overrides are used. It is only intended for ad-hoc customisation, - such as in <filename>~/.config/nixpkgs/config.nix</filename>. - </para> - </warning> - - <para> - The function <varname>overrideDerivation</varname> creates a new derivation - based on an existing one by overriding the original's attributes with the - attribute set produced by the specified function. This function is - available on all derivations defined using the - <varname>makeOverridable</varname> function. Most standard - derivation-producing functions, such as - <varname>stdenv.mkDerivation</varname>, are defined using this function, - which means most packages in the nixpkgs expression, - <varname>pkgs</varname>, have this function. - </para> - - <para> - Example usage: -<programlisting> -mySed = pkgs.gnused.overrideDerivation (oldAttrs: { - name = "sed-4.2.2-pre"; - src = fetchurl { - url = ftp://alpha.gnu.org/gnu/sed/sed-4.2.2-pre.tar.bz2; - sha256 = "11nq06d131y4wmf3drm0yk502d2xc6n5qy82cg88rb9nqd2lj41k"; - }; - patches = []; -}); -</programlisting> - </para> - - <para> - In the above example, the <varname>name</varname>, <varname>src</varname>, - and <varname>patches</varname> of the derivation will be overridden, while - all other attributes will be retained from the original derivation. - </para> - - <para> - The argument <varname>oldAttrs</varname> is used to refer to the attribute - set of the original derivation. - </para> - - <note> - <para> - A package's attributes are evaluated *before* being modified by the - <varname>overrideDerivation</varname> function. For example, the - <varname>name</varname> attribute reference in <varname>url = - "mirror://gnu/hello/${name}.tar.gz";</varname> is filled-in *before* the - <varname>overrideDerivation</varname> function modifies the attribute set. - This means that overriding the <varname>name</varname> attribute, in this - example, *will not* change the value of the <varname>url</varname> - attribute. Instead, we need to override both the <varname>name</varname> - *and* <varname>url</varname> attributes. - </para> - </note> - </section> - - <section xml:id="sec-lib-makeOverridable"> - <title>lib.makeOverridable</title> - - <para> - The function <varname>lib.makeOverridable</varname> is used to make the - result of a function easily customizable. This utility only makes sense for - functions that accept an argument set and return an attribute set. - </para> - - <para> - Example usage: -<programlisting> -f = { a, b }: { result = a+b; }; -c = lib.makeOverridable f { a = 1; b = 2; }; -</programlisting> - </para> - - <para> - The variable <varname>c</varname> is the value of the <varname>f</varname> - function applied with some default arguments. Hence the value of - <varname>c.result</varname> is <literal>3</literal>, in this example. - </para> - - <para> - The variable <varname>c</varname> however also has some additional - functions, like <link linkend="sec-pkg-override">c.override</link> which - can be used to override the default arguments. In this example the value of - <varname>(c.override { a = 4; }).result</varname> is 6. - </para> - </section> - </section> - <section xml:id="sec-generators"> - <title>Generators</title> - - <para> - Generators are functions that create file formats from nix data structures, - e. g. for configuration files. There are generators available for: - <literal>INI</literal>, <literal>JSON</literal> and <literal>YAML</literal> - </para> - - <para> - All generators follow a similar call interface: <code>generatorName - configFunctions data</code>, where <literal>configFunctions</literal> is an - attrset of user-defined functions that format nested parts of the content. - They each have common defaults, so often they do not need to be set - manually. An example is <code>mkSectionName ? (name: libStr.escape [ "[" "]" - ] name)</code> from the <literal>INI</literal> generator. It receives the - name of a section and sanitizes it. The default - <literal>mkSectionName</literal> escapes <literal>[</literal> and - <literal>]</literal> with a backslash. - </para> - - <para> - Generators can be fine-tuned to produce exactly the file format required by - your application/service. One example is an INI-file format which uses - <literal>: </literal> as separator, the strings - <literal>"yes"</literal>/<literal>"no"</literal> as boolean values and - requires all string values to be quoted: - </para> - -<programlisting> -with lib; -let - customToINI = generators.toINI { - # specifies how to format a key/value pair - mkKeyValue = generators.mkKeyValueDefault { - # specifies the generated string for a subset of nix values - mkValueString = v: - if v == true then ''"yes"'' - else if v == false then ''"no"'' - else if isString v then ''"${v}"'' - # and delegats all other values to the default generator - else generators.mkValueStringDefault {} v; - } ":"; - }; - -# the INI file can now be given as plain old nix values -in customToINI { - main = { - pushinfo = true; - autopush = false; - host = "localhost"; - port = 42; - }; - mergetool = { - merge = "diff3"; - }; -} -</programlisting> - - <para> - This will produce the following INI file as nix string: - </para> - -<programlisting> -[main] -autopush:"no" -host:"localhost" -port:42 -pushinfo:"yes" -str\:ange:"very::strange" - -[mergetool] -merge:"diff3" -</programlisting> - - <note> - <para> - Nix store paths can be converted to strings by enclosing a derivation - attribute like so: <code>"${drv}"</code>. - </para> - </note> - - <para> - Detailed documentation for each generator can be found in - <literal>lib/generators.nix</literal>. - </para> - </section> - <section xml:id="sec-debug"> - <title>Debugging Nix Expressions</title> - - <para> - Nix is a unityped, dynamic language, this means every value can potentially - appear anywhere. Since it is also non-strict, evaluation order and what - ultimately is evaluated might surprise you. Therefore it is important to be - able to debug nix expressions. - </para> - - <para> - In the <literal>lib/debug.nix</literal> file you will find a number of - functions that help (pretty-)printing values while evaluation is runnnig. - You can even specify how deep these values should be printed recursively, - and transform them on the fly. Please consult the docstrings in - <literal>lib/debug.nix</literal> for usage information. - </para> - </section> - <section xml:id="sec-fhs-environments"> - <title>buildFHSUserEnv</title> - - <para> - <function>buildFHSUserEnv</function> provides a way to build and run - FHS-compatible lightweight sandboxes. It creates an isolated root with bound - <filename>/nix/store</filename>, so its footprint in terms of disk space - needed is quite small. This allows one to run software which is hard or - unfeasible to patch for NixOS -- 3rd-party source trees with FHS - assumptions, games distributed as tarballs, software with integrity checking - and/or external self-updated binaries. It uses Linux namespaces feature to - create temporary lightweight environments which are destroyed after all - child processes exit, without root user rights requirement. Accepted - arguments are: - </para> - - <variablelist> - <varlistentry> - <term> - <literal>name</literal> - </term> - <listitem> - <para> - Environment name. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <literal>targetPkgs</literal> - </term> - <listitem> - <para> - Packages to be installed for the main host's architecture (i.e. x86_64 on - x86_64 installations). Along with libraries binaries are also installed. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <literal>multiPkgs</literal> - </term> - <listitem> - <para> - Packages to be installed for all architectures supported by a host (i.e. - i686 and x86_64 on x86_64 installations). Only libraries are installed by - default. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <literal>extraBuildCommands</literal> - </term> - <listitem> - <para> - Additional commands to be executed for finalizing the directory - structure. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <literal>extraBuildCommandsMulti</literal> - </term> - <listitem> - <para> - Like <literal>extraBuildCommands</literal>, but executed only on multilib - architectures. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <literal>extraOutputsToInstall</literal> - </term> - <listitem> - <para> - Additional derivation outputs to be linked for both target and - multi-architecture packages. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <literal>extraInstallCommands</literal> - </term> - <listitem> - <para> - Additional commands to be executed for finalizing the derivation with - runner script. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <literal>runScript</literal> - </term> - <listitem> - <para> - A command that would be executed inside the sandbox and passed all the - command line arguments. It defaults to <literal>bash</literal>. - </para> - </listitem> - </varlistentry> - </variablelist> - - <para> - One can create a simple environment using a <literal>shell.nix</literal> - like that: - </para> - -<programlisting><![CDATA[ -{ pkgs ? import <nixpkgs> {} }: - -(pkgs.buildFHSUserEnv { - name = "simple-x11-env"; - targetPkgs = pkgs: (with pkgs; - [ udev - alsaLib - ]) ++ (with pkgs.xorg; - [ libX11 - libXcursor - libXrandr - ]); - multiPkgs = pkgs: (with pkgs; - [ udev - alsaLib - ]); - runScript = "bash"; -}).env -]]></programlisting> - - <para> - Running <literal>nix-shell</literal> would then drop you into a shell with - these libraries and binaries available. You can use this to run - closed-source applications which expect FHS structure without hassles: - simply change <literal>runScript</literal> to the application path, e.g. - <filename>./bin/start.sh</filename> -- relative paths are supported. - </para> - </section> - <xi:include href="shell.section.xml" /> - <section xml:id="sec-pkgs-dockerTools"> - <title>pkgs.dockerTools</title> - - <para> - <varname>pkgs.dockerTools</varname> is a set of functions for creating and - manipulating Docker images according to the - <link xlink:href="https://github.com/moby/moby/blob/master/image/spec/v1.2.md#docker-image-specification-v120"> - Docker Image Specification v1.2.0 </link>. Docker itself is not used to - perform any of the operations done by these functions. - </para> - - <warning> - <para> - The <varname>dockerTools</varname> API is unstable and may be subject to - backwards-incompatible changes in the future. - </para> - </warning> - - <section xml:id="ssec-pkgs-dockerTools-buildImage"> - <title>buildImage</title> - - <para> - This function is analogous to the <command>docker build</command> command, - in that can used to build a Docker-compatible repository tarball containing - a single image with one or multiple layers. As such, the result is suitable - for being loaded in Docker with <command>docker load</command>. - </para> - - <para> - The parameters of <varname>buildImage</varname> with relative example - values are described below: - </para> - - <example xml:id='ex-dockerTools-buildImage'> - <title>Docker build</title> -<programlisting> -buildImage { - name = "redis"; <co xml:id='ex-dockerTools-buildImage-1' /> - tag = "latest"; <co xml:id='ex-dockerTools-buildImage-2' /> - - fromImage = someBaseImage; <co xml:id='ex-dockerTools-buildImage-3' /> - fromImageName = null; <co xml:id='ex-dockerTools-buildImage-4' /> - fromImageTag = "latest"; <co xml:id='ex-dockerTools-buildImage-5' /> - - contents = pkgs.redis; <co xml:id='ex-dockerTools-buildImage-6' /> - runAsRoot = '' <co xml:id='ex-dockerTools-buildImage-runAsRoot' /> - #!${stdenv.shell} - mkdir -p /data - ''; - - config = { <co xml:id='ex-dockerTools-buildImage-8' /> - Cmd = [ "/bin/redis-server" ]; - WorkingDir = "/data"; - Volumes = { - "/data" = {}; - }; - }; -} -</programlisting> - </example> - - <para> - The above example will build a Docker image <literal>redis/latest</literal> - from the given base image. Loading and running this image in Docker results - in <literal>redis-server</literal> being started automatically. - </para> - - <calloutlist> - <callout arearefs='ex-dockerTools-buildImage-1'> - <para> - <varname>name</varname> specifies the name of the resulting image. This - is the only required argument for <varname>buildImage</varname>. - </para> - </callout> - <callout arearefs='ex-dockerTools-buildImage-2'> - <para> - <varname>tag</varname> specifies the tag of the resulting image. By - default it's <literal>null</literal>, which indicates that the nix output - hash will be used as tag. - </para> - </callout> - <callout arearefs='ex-dockerTools-buildImage-3'> - <para> - <varname>fromImage</varname> is the repository tarball containing the - base image. It must be a valid Docker image, such as exported by - <command>docker save</command>. By default it's <literal>null</literal>, - which can be seen as equivalent to <literal>FROM scratch</literal> of a - <filename>Dockerfile</filename>. - </para> - </callout> - <callout arearefs='ex-dockerTools-buildImage-4'> - <para> - <varname>fromImageName</varname> can be used to further specify the base - image within the repository, in case it contains multiple images. By - default it's <literal>null</literal>, in which case - <varname>buildImage</varname> will peek the first image available in the - repository. - </para> - </callout> - <callout arearefs='ex-dockerTools-buildImage-5'> - <para> - <varname>fromImageTag</varname> can be used to further specify the tag of - the base image within the repository, in case an image contains multiple - tags. By default it's <literal>null</literal>, in which case - <varname>buildImage</varname> will peek the first tag available for the - base image. - </para> - </callout> - <callout arearefs='ex-dockerTools-buildImage-6'> - <para> - <varname>contents</varname> is a derivation that will be copied in the - new layer of the resulting image. This can be similarly seen as - <command>ADD contents/ /</command> in a <filename>Dockerfile</filename>. - By default it's <literal>null</literal>. - </para> - </callout> - <callout arearefs='ex-dockerTools-buildImage-runAsRoot'> - <para> - <varname>runAsRoot</varname> is a bash script that will run as root in an - environment that overlays the existing layers of the base image with the - new resulting layer, including the previously copied - <varname>contents</varname> derivation. This can be similarly seen as - <command>RUN ...</command> in a <filename>Dockerfile</filename>. - <note> - <para> - Using this parameter requires the <literal>kvm</literal> device to be - available. - </para> - </note> - </para> - </callout> - <callout arearefs='ex-dockerTools-buildImage-8'> - <para> - <varname>config</varname> is used to specify the configuration of the - containers that will be started off the built image in Docker. The - available options are listed in the - <link xlink:href="https://github.com/moby/moby/blob/master/image/spec/v1.2.md#image-json-field-descriptions"> - Docker Image Specification v1.2.0 </link>. - </para> - </callout> - </calloutlist> - - <para> - After the new layer has been created, its closure (to which - <varname>contents</varname>, <varname>config</varname> and - <varname>runAsRoot</varname> contribute) will be copied in the layer - itself. Only new dependencies that are not already in the existing layers - will be copied. - </para> - - <para> - At the end of the process, only one new single layer will be produced and - added to the resulting image. - </para> - - <para> - The resulting repository will only list the single image - <varname>image/tag</varname>. In the case of - <xref linkend='ex-dockerTools-buildImage'/> it would be - <varname>redis/latest</varname>. - </para> - - <para> - It is possible to inspect the arguments with which an image was built using - its <varname>buildArgs</varname> attribute. - </para> - - <note> - <para> - If you see errors similar to <literal>getProtocolByName: does not exist - (no such protocol name: tcp)</literal> you may need to add - <literal>pkgs.iana-etc</literal> to <varname>contents</varname>. - </para> - </note> - - <note> - <para> - If you see errors similar to <literal>Error_Protocol ("certificate has - unknown CA",True,UnknownCa)</literal> you may need to add - <literal>pkgs.cacert</literal> to <varname>contents</varname>. - </para> - </note> - - <example xml:id="example-pkgs-dockerTools-buildImage-creation-date"> - <title>Impurely Defining a Docker Layer's Creation Date</title> - <para> - By default <function>buildImage</function> will use a static - date of one second past the UNIX Epoch. This allows - <function>buildImage</function> to produce binary reproducible - images. When listing images with <command>docker list - images</command>, the newly created images will be listed like - this: - </para> - <screen><![CDATA[ -$ docker image list -REPOSITORY TAG IMAGE ID CREATED SIZE -hello latest 08c791c7846e 48 years ago 25.2MB -]]></screen> - <para> - You can break binary reproducibility but have a sorted, - meaningful <literal>CREATED</literal> column by setting - <literal>created</literal> to <literal>now</literal>. - </para> - <programlisting><![CDATA[ -pkgs.dockerTools.buildImage { - name = "hello"; - tag = "latest"; - created = "now"; - contents = pkgs.hello; - - config.Cmd = [ "/bin/hello" ]; -} -]]></programlisting> - <para> - and now the Docker CLI will display a reasonable date and - sort the images as expected: - <screen><![CDATA[ -$ docker image list -REPOSITORY TAG IMAGE ID CREATED SIZE -hello latest de2bf4786de6 About a minute ago 25.2MB -]]></screen> - however, the produced images will not be binary reproducible. - </para> - </example> - </section> - - <section xml:id="ssec-pkgs-dockerTools-buildLayeredImage"> - <title>buildLayeredImage</title> - - <para> - Create a Docker image with many of the store paths being on their own layer - to improve sharing between images. - </para> - - <variablelist> - <varlistentry> - <term> - <varname>name</varname> - </term> - <listitem> - <para> - The name of the resulting image. - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <varname>tag</varname> <emphasis>optional</emphasis> - </term> - <listitem> - <para> - Tag of the generated image. - </para> - <para> - <emphasis>Default:</emphasis> the output path's hash - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <varname>contents</varname> <emphasis>optional</emphasis> - </term> - <listitem> - <para> - Top level paths in the container. Either a single derivation, or a list - of derivations. - </para> - <para> - <emphasis>Default:</emphasis> <literal>[]</literal> - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <varname>config</varname> <emphasis>optional</emphasis> - </term> - <listitem> - <para> - Run-time configuration of the container. A full list of the options are - available at in the - <link xlink:href="https://github.com/moby/moby/blob/master/image/spec/v1.2.md#image-json-field-descriptions"> - Docker Image Specification v1.2.0 </link>. - </para> - <para> - <emphasis>Default:</emphasis> <literal>{}</literal> - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <varname>created</varname> <emphasis>optional</emphasis> - </term> - <listitem> - <para> - Date and time the layers were created. Follows the same - <literal>now</literal> exception supported by - <literal>buildImage</literal>. - </para> - <para> - <emphasis>Default:</emphasis> <literal>1970-01-01T00:00:01Z</literal> - </para> - </listitem> - </varlistentry> - <varlistentry> - <term> - <varname>maxLayers</varname> <emphasis>optional</emphasis> - </term> - <listitem> - <para> - Maximum number of layers to create. - </para> - <para> - <emphasis>Default:</emphasis> <literal>24</literal> - </para> - </listitem> - </varlistentry> - </variablelist> - - <section xml:id="dockerTools-buildLayeredImage-arg-contents"> - <title>Behavior of <varname>contents</varname> in the final image</title> - - <para> - Each path directly listed in <varname>contents</varname> will have a - symlink in the root of the image. - </para> - - <para> - For example: -<programlisting><![CDATA[ -pkgs.dockerTools.buildLayeredImage { - name = "hello"; - contents = [ pkgs.hello ]; -} -]]></programlisting> - will create symlinks for all the paths in the <literal>hello</literal> - package: -<screen><![CDATA[ -/bin/hello -> /nix/store/h1zb1padqbbb7jicsvkmrym3r6snphxg-hello-2.10/bin/hello -/share/info/hello.info -> /nix/store/h1zb1padqbbb7jicsvkmrym3r6snphxg-hello-2.10/share/info/hello.info -/share/locale/bg/LC_MESSAGES/hello.mo -> /nix/store/h1zb1padqbbb7jicsvkmrym3r6snphxg-hello-2.10/share/locale/bg/LC_MESSAGES/hello.mo -]]></screen> - </para> - </section> - - <section xml:id="dockerTools-buildLayeredImage-arg-config"> - <title>Automatic inclusion of <varname>config</varname> references</title> - - <para> - The closure of <varname>config</varname> is automatically included in the - closure of the final image. - </para> - - <para> - This allows you to make very simple Docker images with very little code. - This container will start up and run <command>hello</command>: -<programlisting><![CDATA[ -pkgs.dockerTools.buildLayeredImage { - name = "hello"; - config.Cmd = [ "${pkgs.hello}/bin/hello" ]; -} -]]></programlisting> - </para> - </section> - - <section xml:id="dockerTools-buildLayeredImage-arg-maxLayers"> - <title>Adjusting <varname>maxLayers</varname></title> - - <para> - Increasing the <varname>maxLayers</varname> increases the number of layers - which have a chance to be shared between different images. - </para> - - <para> - Modern Docker installations support up to 128 layers, however older - versions support as few as 42. - </para> - - <para> - If the produced image will not be extended by other Docker builds, it is - safe to set <varname>maxLayers</varname> to <literal>128</literal>. - However it will be impossible to extend the image further. - </para> - - <para> - The first (<literal>maxLayers-2</literal>) most "popular" paths will have - their own individual layers, then layer #<literal>maxLayers-1</literal> - will contain all the remaining "unpopular" paths, and finally layer - #<literal>maxLayers</literal> will contain the Image configuration. - </para> - - <para> - Docker's Layers are not inherently ordered, they are content-addressable - and are not explicitly layered until they are composed in to an Image. - </para> - </section> - </section> - - <section xml:id="ssec-pkgs-dockerTools-fetchFromRegistry"> - <title>pullImage</title> - - <para> - This function is analogous to the <command>docker pull</command> command, - in that can be used to pull a Docker image from a Docker registry. By - default <link xlink:href="https://hub.docker.com/">Docker Hub</link> is - used to pull images. - </para> - - <para> - Its parameters are described in the example below: - </para> - - <example xml:id='ex-dockerTools-pullImage'> - <title>Docker pull</title> -<programlisting> -pullImage { - imageName = "nixos/nix"; <co xml:id='ex-dockerTools-pullImage-1' /> - imageDigest = "sha256:20d9485b25ecfd89204e843a962c1bd70e9cc6858d65d7f5fadc340246e2116b"; <co xml:id='ex-dockerTools-pullImage-2' /> - finalImageTag = "1.11"; <co xml:id='ex-dockerTools-pullImage-3' /> - sha256 = "0mqjy3zq2v6rrhizgb9nvhczl87lcfphq9601wcprdika2jz7qh8"; <co xml:id='ex-dockerTools-pullImage-4' /> - os = "linux"; <co xml:id='ex-dockerTools-pullImage-5' /> - arch = "x86_64"; <co xml:id='ex-dockerTools-pullImage-6' /> -} -</programlisting> - </example> - - <calloutlist> - <callout arearefs='ex-dockerTools-pullImage-1'> - <para> - <varname>imageName</varname> specifies the name of the image to be - downloaded, which can also include the registry namespace (e.g. - <literal>nixos</literal>). This argument is required. - </para> - </callout> - <callout arearefs='ex-dockerTools-pullImage-2'> - <para> - <varname>imageDigest</varname> specifies the digest of the image to be - downloaded. Skopeo can be used to get the digest of an image, with its - <varname>inspect</varname> subcommand. Since a given - <varname>imageName</varname> may transparently refer to a manifest list - of images which support multiple architectures and/or operating systems, - supply the `--override-os` and `--override-arch` arguments to specify - exactly which image you want. By default it will match the OS and - architecture of the host the command is run on. -<programlisting> -$ 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'" -sha256:20d9485b25ecfd89204e843a962c1bd70e9cc6858d65d7f5fadc340246e2116b -</programlisting> - This argument is required. - </para> - </callout> - <callout arearefs='ex-dockerTools-pullImage-3'> - <para> - <varname>finalImageTag</varname>, if specified, this is the tag of the - image to be created. Note it is never used to fetch the image since we - prefer to rely on the immutable digest ID. By default it's - <literal>latest</literal>. - </para> - </callout> - <callout arearefs='ex-dockerTools-pullImage-4'> - <para> - <varname>sha256</varname> is the checksum of the whole fetched image. - This argument is required. - </para> - </callout> - <callout arearefs='ex-dockerTools-pullImage-5'> - <para> - <varname>os</varname>, if specified, is the operating system of the - fetched image. By default it's <literal>linux</literal>. - </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 can 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 = '' - #!${stdenv.shell} - ${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> are necessary for shadow-utils to - manipulate users and groups. - </para> - </section> - </section> + <xi:include href="functions/overrides.xml" /> + <xi:include href="functions/generators.xml" /> + <xi:include href="functions/debug.xml" /> + <xi:include href="functions/fhs-environments.xml" /> + <xi:include href="functions/shell.xml" /> + <xi:include href="functions/dockertools.xml" /> </chapter> |