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dockerTools.buildImage: support impure dates

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Because dates are an impurity, by default buildImage will use a static
date of one second past the UNIX Epoch. This can be a bit frustrating
when listing docker images in the CLI:

    $ docker image list
    REPOSITORY   TAG      IMAGE ID       CREATED        SIZE
    hello        latest   08c791c7846e   48 years ago   25.2MB

If you want to trade the purity for a better user experience, you can
set created to now.

    pkgs.dockerTools.buildImage {
      name = "hello";
      tag = "latest";
      created = "now";
      contents = pkgs.hello;

      config.Cmd = [ "/bin/hello" ];
    }

and now the Docker CLI will display a reasonable date and sort the
images as expected:

    $ docker image list
    REPOSITORY   TAG      IMAGE ID       CREATED              SIZE
    hello        latest   de2bf4786de6   About a minute ago   25.2MB
This commit is contained in:
Graham Christensen 2018-09-20 11:40:36 -04:00 committed by Robin Gloster
parent b0987f2013
commit a32d7e0c74
2 changed files with 52 additions and 6 deletions
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39
doc/functions.xml
View File

@ -638,6 +638,45 @@ buildImage {
<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>
Because dates are an impurity, by default
<function>buildImage</function> will use a static date of one
second past the UNIX Epoch. This can be a bit frustrating when
listing docker images in the CLI:
</para>
<screen><![CDATA[
$ docker image list
REPOSITORY TAG IMAGE ID CREATED SIZE
hello latest 08c791c7846e 48 years ago 25.2MB
]]></screen>
<para>
If you want to trade the purity for a better user experience,
you can set <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:
</para>
<screen><![CDATA[
$ docker image list
REPOSITORY TAG IMAGE ID CREATED SIZE
hello latest de2bf4786de6 About a minute ago 25.2MB
]]></screen>
</example>
</section>
<section xml:id="ssec-pkgs-dockerTools-fetchFromRegistry">

19
pkgs/build-support/docker/default.nix
View File

@ -450,11 +450,18 @@ rec {
baseName = baseNameOf name;
# Create a JSON blob of the configuration. Set the date to unix zero.
baseJson = writeText "${baseName}-config.json" (builtins.toJSON {
inherit created config;
architecture = "amd64";
os = "linux";
});
baseJson = let
pure = writeText "${baseName}-config.json" (builtins.toJSON {
inherit created config;
architecture = "amd64";
os = "linux";
});
impure = runCommand "${baseName}-config.json"
{ buildInputs = [ jq ]; }
''
jq ".created = \"$(TZ=utc date --iso-8601="seconds")\"" ${pure} > $out
'';
in if created == "now" then impure else pure;
layer =
if runAsRoot == null
@ -577,7 +584,7 @@ rec {
currentID=$layerID
while [[ -n "$currentID" ]]; do
layerChecksum=$(sha256sum image/$currentID/layer.tar | cut -d ' ' -f1)
imageJson=$(echo "$imageJson" | jq ".history |= [{\"created\": \"${created}\"}] + .")
imageJson=$(echo "$imageJson" | jq ".history |= [{\"created\": \"$(jq -r .created ${baseJson})\"}] + .")
imageJson=$(echo "$imageJson" | jq ".rootfs.diff_ids |= [\"sha256:$layerChecksum\"] + .")
manifestJson=$(echo "$manifestJson" | jq ".[0].Layers |= [\"$currentID/layer.tar\"] + .")