forked from mirrors/nixpkgs
4fe9006190
Create a many-layered Docker Image.
Implements much less than buildImage:
- Doesn't support specific uids/gids
- Doesn't support runninng commands after building
- Doesn't require qemu
- Doesn't create mutable copies of the files in the path
- Doesn't support parent images
If you want those feature, I recommend using buildLayeredImage as an
input to buildImage.
Notably, it does support:
- Caching low level, common paths based on a graph traversial
algorithm, see referencesByPopularity in
0a80233487993256e811f566b1c80a40394c03d6
- Configurable number of layers. If you're not using AUFS or not
extending the image, you can specify a larger number of layers at
build time:
pkgs.dockerTools.buildLayeredImage {
name = "hello";
maxLayers = 128;
config.Cmd = [ "${pkgs.gitFull}/bin/git" ];
};
- Parallelized creation of the layers, improving build speed.
- The contents of the image includes the closure of the configuration,
so you don't have to specify paths in contents and config.
With buildImage, paths referred to by the config were not included
automatically in the image. Thus, if you wanted to call Git, you
had to specify it twice:
pkgs.dockerTools.buildImage {
name = "hello";
contents = [ pkgs.gitFull ];
config.Cmd = [ "${pkgs.gitFull}/bin/git" ];
};
buildLayeredImage on the other hand includes the runtime closure of
the config when calculating the contents of the image:
pkgs.dockerTools.buildImage {
name = "hello";
config.Cmd = [ "${pkgs.gitFull}/bin/git" ];
};
Minor Problems
- If any of the store paths change, every layer will be rebuilt in
the nix-build. However, beacuse the layers are bit-for-bit
reproducable, when these images are loaded in to Docker they will
match existing layers and not be imported or uploaded twice.
Common Questions
- Aren't Docker layers ordered?
No. People who have used a Dockerfile before assume Docker's
Layers are inherently ordered. However, this is not true -- Docker
layers are content-addressable and are not explicitly layered until
they are composed in to an Image.
- What happens if I have more than maxLayers of store paths?
The first (maxLayers-2) most "popular" paths will have their own
individual layers, then layer #(maxLayers-1) will contain all the
remaining "unpopular" paths, and finally layer #(maxLayers) will
contain the Image configuration.
1029 lines
34 KiB
XML
1029 lines
34 KiB
XML
<chapter xmlns="http://docbook.org/ns/docbook"
|
||
xmlns:xlink="http://www.w3.org/1999/xlink"
|
||
xmlns:xi="http://www.w3.org/2001/XInclude"
|
||
xml:id="chap-functions">
|
||
<title>Functions reference</title>
|
||
<para>
|
||
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 is different from <function>pkgs.dockerTools.buildImage</function>
|
||
which does <emphasis>not</emphasis> automatically include the
|
||
configuration's closure.
|
||
</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>
|
||
</chapter>
|