iSharkFly-Docs
/
packer-cn
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

website: new config template docs

This commit is contained in:
Mitchell Hashimoto 2013-08-08 16:56:09 -07:00
parent 1b01e82d8d
commit 16ccfe3824
1 changed files with 28 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
website/source/docs/templates/configuration-templates.html.markdown vendored
View File

@ -4,34 +4,32 @@ layout: "docs"
# Configuration Templates
Certain configuration parameters within templates are themselves a
type of "template." These are not Packer templates, but text templates,
where variables can be used to modify the value of a configuration parameter
during runtime.
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.
For example, the `ami_name` configuration for the [AMI builder](/docs/builders/amazon-ebs.html)
is a template. An example value may be `My Packer AMI {{.CreateTime}}`. At
runtime, this will be turned into `My Packer AMI 1370900368`, where the
"CreateTime" variable was replaced with the Unix timestamp of when the
AMI was actually created.
For example, the `{{timestamp}}` function can be used in any string to
generate the current timestamp. This is useful for configurations that require
unique keys, such as AMI names. By setting the AMI name to something like
`My Packer AMI {{timestamp}}`, the AMI name will be unique down to the second.
This sort of templating is pervasive throughout Packer. Instead of documenting
the templating syntax in each location, it is documented once here so
you know how to use it.
In addition to globally available functions like timestamp shown before,
some configurations have special local variables that are available only
for that configuration. These are recognizable because they're prefixed by
a period, such as `{{.Name}}`.
<div class="alert alert-info">
<strong>For advanced users:</strong> The templates are actually parsed and executed
using Go's <a href="http://golang.org/pkg/text/template/">text/template</a>
package. It therefore supports the complete template syntax.
</div>
The complete syntax is covered in the next section, followed by a reference
of globally available functions.
## Syntax
99% of the time all you'll need within configuration templates are variables.
Variables are accessed by using `{{.VARIABLENAME}}`. The "." prefixing the
variable name signals that you're accessing a variable on the root
template object. All template directives go between braces. Here is a piece
of a VMware VMX template that uses variables:
The syntax of templates is extremely simple. Anything template related
happens within double-braces: `{{ }}`. Variables are prefixed with a period
and capitalized, such as `{{.Variable}}` and functions are just directly
within the braces, such as `{{timestamp}}`.
Here is an example from the VMware VMX template that shows configuration
templates in action:
<pre>
.encoding = "UTF-8"
@ -47,3 +45,11 @@ resulting in a VMX that looks like this:
displayName = "packer"
guestOS = "otherlinux"
</pre>
## Global Functions
While some configuration settings have local variables specific to only that
configuration, a set of functions are available globally for use in _any string_
in Packer templates. These are listed below for reference.
* ``timestamp`` - The current Unix timestamp in UTC.