From c7555762f3a30190ce7726b4d013bc3e83c7e4b6 Mon Sep 17 00:00:00 2001 From: Chad Smith Date: Tue, 11 Sep 2018 17:31:46 +0000 Subject: user-data: jinja template to render instance-data.json in cloud-config Allow users to provide '## template: jinja' as the first line or their #cloud-config or custom script user-data parts. When this header exists, the cloud-config or script will be rendered as a jinja template. All instance metadata keys and values present in /run/cloud-init/instance-data.json will be available as jinja variables for the template. This means any cloud-config module or script can reference any standardized instance data in templates and scripts. Additionally, any standardized instance-data.json keys scoped below a '' key will be promoted as a top-level key for ease of reference in templates. This means that '{{ local_hostname }}' is the same as using the latest '{{ v#.local_hostname }}'. Since instance-data is written to /run/cloud-init/instance-data.json, make sure it is persisted across reboots when the cached datasource opject is reloaded. LP: #1791781 --- doc/rtd/topics/capabilities.rst | 15 ++++++++++--- doc/rtd/topics/datasources.rst | 47 +++++++++++++++++++++++++++++++++++++++++ doc/rtd/topics/format.rst | 21 ++++++++++++++---- 3 files changed, 76 insertions(+), 7 deletions(-) (limited to 'doc') diff --git a/doc/rtd/topics/capabilities.rst b/doc/rtd/topics/capabilities.rst index 3e2c9e31..2d8e2538 100644 --- a/doc/rtd/topics/capabilities.rst +++ b/doc/rtd/topics/capabilities.rst @@ -16,13 +16,15 @@ User configurability `Cloud-init`_ 's behavior can be configured via user-data. - User-data can be given by the user at instance launch time. + User-data can be given by the user at instance launch time. See + :ref:`user_data_formats` for acceptable user-data content. + This is done via the ``--user-data`` or ``--user-data-file`` argument to ec2-run-instances for example. -* Check your local clients documentation for how to provide a `user-data` - string or `user-data` file for usage by cloud-init on instance creation. +* Check your local client's documentation for how to provide a `user-data` + string or `user-data` file to cloud-init on instance creation. Feature detection @@ -166,6 +168,13 @@ likely be promoted to top-level subcommands when stable. validation is work in progress and supports a subset of cloud-config modules. + * ``cloud-init devel render``: Use cloud-init's jinja template render to + process **#cloud-config** or **custom-scripts**, injecting any variables + from ``/run/cloud-init/instance-data.json``. It accepts a user-data file + containing the jinja template header ``## template: jinja`` and renders + that content with any instance-data.json variables present. + + .. _cli_clean: cloud-init clean diff --git a/doc/rtd/topics/datasources.rst b/doc/rtd/topics/datasources.rst index 83034589..14432e65 100644 --- a/doc/rtd/topics/datasources.rst +++ b/doc/rtd/topics/datasources.rst @@ -18,6 +18,8 @@ single way to access the different cloud systems methods to provide this data through the typical usage of subclasses. +.. _instance_metadata: + instance-data ------------- For reference, cloud-init stores all the metadata, vendordata and userdata @@ -110,6 +112,51 @@ Below is an instance-data.json example from an OpenStack instance: } } + +As of cloud-init v. 18.4, any values present in +``/run/cloud-init/instance-data.json`` can be used in cloud-init user data +scripts or cloud config data. This allows consumers to use cloud-init's +vendor-neutral, standardized metadata keys as well as datasource-specific +content for any scripts or cloud-config modules they are using. + +To use instance-data.json values in scripts and **#config-config** files the +user-data will need to contain the following header as the first line **## template: jinja**. Cloud-init will source all variables defined in +``/run/cloud-init/instance-data.json`` and allow scripts or cloud-config files +to reference those paths. Below are two examples:: + + * Cloud config calling home with the ec2 public hostname and avaliability-zone + ``` + ## template: jinja + #cloud-config + runcmd: + - echo 'EC2 public hostname allocated to instance: {{ ds.meta_data.public_hostname }}' > /tmp/instance_metadata + - echo 'EC2 avaiability zone: {{ v1.availability_zone }}' >> /tmp/instance_metadata + - curl -X POST -d '{"hostname": "{{ds.meta_data.public_hostname }}", "availability-zone": "{{ v1.availability_zone }}"}' https://example.com.com + ``` + + * Custom user script performing different operations based on region + ``` + ## template: jinja + #!/bin/bash + {% if v1.region == 'us-east-2' -%} + echo 'Installing custom proxies for {{ v1.region }} + sudo apt-get install my-xtra-fast-stack + {%- endif %} + ... + + ``` + +.. note:: + Trying to reference jinja variables that don't exist in + instance-data.json will result in warnings in ``/var/log/cloud-init.log`` + and the following string in your rendered user-data: + ``CI_MISSING_JINJA_VAR/``. + +.. note:: + To save time designing your user-data for a specific cloud's + instance-data.json, use the 'render' cloud-init command on an + instance booted on your favorite cloud. See :ref:`cli_devel` for more + information. Datasource API diff --git a/doc/rtd/topics/format.rst b/doc/rtd/topics/format.rst index 1b0ff366..15234d21 100644 --- a/doc/rtd/topics/format.rst +++ b/doc/rtd/topics/format.rst @@ -1,6 +1,8 @@ -******* -Formats -******* +.. _user_data_formats: + +***************** +User-Data Formats +***************** User data that will be acted upon by cloud-init must be in one of the following types. @@ -65,6 +67,11 @@ Typically used by those who just want to execute a shell script. Begins with: ``#!`` or ``Content-Type: text/x-shellscript`` when using a MIME archive. +.. note:: + New in cloud-init v. 18.4: User-data scripts can also render cloud instance + metadata variables using jinja templating. See + :ref:`instance_metadata` for more information. + Example ------- @@ -103,12 +110,18 @@ These things include: - certain ssh keys should be imported - *and many more...* -**Note:** The file must be valid yaml syntax. +.. note:: + This file must be valid yaml syntax. See the :ref:`yaml_examples` section for a commented set of examples of supported cloud config formats. Begins with: ``#cloud-config`` or ``Content-Type: text/cloud-config`` when using a MIME archive. +.. note:: + New in cloud-init v. 18.4: Cloud config dta can also render cloud instance + metadata variables using jinja templating. See + :ref:`instance_metadata` for more information. + Upstart Job =========== -- cgit v1.2.3