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docs	Configuration Templates

Configuration Templates

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 {{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.

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}}.

The complete syntax is covered in the next section, followed by a reference of globally available functions.

Syntax

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:

.encoding = "UTF-8"
displayName = "{{ .Name }}"
guestOS = "{{ .GuestOS }}"

In this case, the "Name" and "GuestOS" variables will be replaced, potentially resulting in a VMX that looks like this:

.encoding = "UTF-8"
displayName = "packer"
guestOS = "otherlinux"

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.