153 lines
4.6 KiB
Markdown
153 lines
4.6 KiB
Markdown
---
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layout: "docs"
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page_title: "Configuration Templates"
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description: |-
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All strings within templates are processed by a common Packer templating engine, where variables and functions can be used to modify the value of a configuration parameter at runtime.
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---
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# Configuration Templates
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All strings within templates are processed by a common Packer templating
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engine, where variables and functions can be used to modify the value of
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a configuration parameter at runtime.
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For example, the `{{timestamp}}` function can be used in any string to
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generate the current timestamp. This is useful for configurations that require
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unique keys, such as AMI names. By setting the AMI name to something like
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`My Packer AMI {{timestamp}}`, the AMI name will be unique down to the second.
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In addition to globally available functions like timestamp shown before,
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some configurations have special local variables that are available only
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for that configuration. These are recognizable because they're prefixed by
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a period, such as `{{.Name}}`.
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The complete syntax is covered in the next section, followed by a reference
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of globally available functions.
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## Syntax
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The syntax of templates is extremely simple. Anything template related
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happens within double-braces: `{{ }}`. Variables are prefixed with a period
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and capitalized, such as `{{.Variable}}` and functions are just directly
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within the braces, such as `{{timestamp}}`.
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Here is an example from the VMware VMX template that shows configuration
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templates in action:
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```liquid
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.encoding = "UTF-8"
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displayName = "{{ .Name }}"
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guestOS = "{{ .GuestOS }}"
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```
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In this case, the "Name" and "GuestOS" variables will be replaced, potentially
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resulting in a VMX that looks like this:
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```liquid
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.encoding = "UTF-8"
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displayName = "packer"
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guestOS = "otherlinux"
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```
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## Global Functions
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While some configuration settings have local variables specific to only that
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configuration, a set of functions are available globally for use in _any string_
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in Packer templates. These are listed below for reference.
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* `build_name` - The name of the build being run.
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* `build_type` - The type of the builder being used currently.
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* `isotime [FORMAT]` - UTC time, which can be [formatted](http://golang.org/pkg/time/#example_Time_Format).
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See more examples below.
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* `lower` - Lowercases the string.
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* `pwd` - The working directory while executing Packer.
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* `template_dir` - The directory to the template for the build.
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* `timestamp` - The current Unix timestamp in UTC.
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* `uuid` - Returns a random UUID.
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* `upper` - Uppercases the string.
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### isotime Format
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Formatting for the function `isotime` uses the magic reference date
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**Mon Jan 2 15:04:05 -0700 MST 2006**, which breaks down to the following:
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<div class="table-responsive">
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<table class="table table-bordered table-condensed">
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<thead>
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<tr>
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<th></th>
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<th align="center">Day of Week</th>
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<th align="center">Month</th>
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<th align="center">Date</th>
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<th align="center">Hour</th>
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<th align="center">Minute</th>
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<th align="center">Second</th>
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<th align="center">Year</th>
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<th align="center">Timezone</th>
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</tr>
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</thead>
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<tr>
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<th>Numeric</th>
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<td align="center">-</td>
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<td align="center">01</td>
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<td align="center">02</td>
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<td align="center">03 (15)</td>
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<td align="center">04</td>
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<td align="center">05</td>
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<td align="center">06</td>
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<td align="center">-0700</td>
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</tr>
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<tr>
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<th>Textual</th>
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<td align="center">Monday (Mon)</td>
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<td align="center">January (Jan)</td>
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<td align="center">-</td>
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<td align="center">-</td>
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<td align="center">-</td>
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<td align="center">-</td>
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<td align="center">-</td>
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<td align="center">MST</td>
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</tr>
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</table>
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</div>
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_The values in parentheses are the abbreviated, or 24-hour clock values_
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Here are some example formated time, using the above format options:
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```liquid
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isotime = June 7, 7:22:43pm 2014
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{{isotime "2006-01-02"}} = 2014-06-07
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{{isotime "Mon 1504"}} = Sat 1922
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{{isotime "02-Jan-06 03\_04\_05"}} = 07-Jun-2014 07\_22\_43
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{{isotime "Hour15Year200603"}} = Hour19Year201407
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```
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Please note that double quote characters need escaping inside of templates:
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```javascript
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{
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"builders": [
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{
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"type": "amazon-ebs",
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"access_key": "...",
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"secret_key": "...",
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"region": "us-east-1",
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"source_ami": "ami-de0d9eb7",
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"instance_type": "t1.micro",
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"ssh_username": "ubuntu",
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"ami_name": "packer {{isotime \"2006-01-02\"}}"
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}
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]
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}
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```
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## Amazon Specific Functions
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Specific to Amazon builders:
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* ``clean_ami_name`` - AMI names can only contain certain characters. This
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function will replace illegal characters with a '-" character. Example usage
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since ":" is not a legal AMI name is: `{{isotime | clean_ami_name}}`.
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