github.com/rahart/packer@v0.12.2-0.20161229105310-282bb6ad370f/website/source/docs/templates/introduction.html.md (about)

     1  ---
     2  description: |
     3      Templates are JSON files that configure the various components of Packer in
     4      order to create one or more machine images. Templates are portable, static, and
     5      readable and writable by both humans and computers. This has the added benefit
     6      of being able to not only create and modify templates by hand, but also write
     7      scripts to dynamically create or modify templates.
     8  layout: docs
     9  page_title: Templates
    10  ...
    11  
    12  # Templates
    13  
    14  Templates are JSON files that configure the various components of Packer in
    15  order to create one or more machine images. Templates are portable, static, and
    16  readable and writable by both humans and computers. This has the added benefit
    17  of being able to not only create and modify templates by hand, but also write
    18  scripts to dynamically create or modify templates.
    19  
    20  Templates are given to commands such as `packer build`, which will take the
    21  template and actually run the builds within it, producing any resulting machine
    22  images.
    23  
    24  ## Template Structure
    25  
    26  A template is a JSON object that has a set of keys configuring various
    27  components of Packer. The available keys within a template are listed below.
    28  Along with each key, it is noted whether it is required or not.
    29  
    30  -   `builders` (*required*) is an array of one or more objects that defines the
    31      builders that will be used to create machine images for this template, and
    32      configures each of those builders. For more information on how to define and
    33      configure a builder, read the sub-section on [configuring builders in
    34      templates](/docs/templates/builders.html).
    35  
    36  -   `description` (optional) is a string providing a description of what the
    37      template does. This output is used only in the [inspect
    38      command](/docs/command-line/inspect.html).
    39  
    40  -   `min_packer_version` (optional) is a string that has a minimum Packer
    41      version that is required to parse the template. This can be used to ensure
    42      that proper versions of Packer are used with the template. A max version
    43      can't be specified because Packer retains backwards compatibility with
    44      `packer fix`.
    45  
    46  -   `post-processors` (optional) is an array of one or more objects that defines
    47      the various post-processing steps to take with the built images. If not
    48      specified, then no post-processing will be done. For more information on
    49      what post-processors do and how they're defined, read the sub-section on
    50      [configuring post-processors in
    51      templates](/docs/templates/post-processors.html).
    52  
    53  -   `provisioners` (optional) is an array of one or more objects that defines
    54      the provisioners that will be used to install and configure software for the
    55      machines created by each of the builders. If it is not specified, then no
    56      provisioners will be run. For more information on how to define and
    57      configure a provisioner, read the sub-section on [configuring provisioners
    58      in templates](/docs/templates/provisioners.html).
    59  
    60  -   `variables` (optional) is an object of one or more key/value strings that
    61      defines user variables contained in the template. If it is not specified,
    62      then no variables are defined. For more information on how to define and use
    63      user variables, read the sub-section on [user variables in
    64      templates](/docs/templates/user-variables.html).
    65  
    66  ## Comments
    67  
    68  JSON doesn't support comments and Packer reports unknown keys as validation
    69  errors. If you'd like to comment your template, you can prefix a *root level*
    70  key with an underscore. Example:
    71  
    72  ``` {.javascript}
    73  {
    74    "_comment": "This is a comment",
    75    "builders": [{}]
    76  }
    77  ```
    78  
    79  **Important:** Only *root level* keys can be underscore prefixed. Keys within
    80  builders, provisioners, etc. will still result in validation errors.
    81  
    82  ## Example Template
    83  
    84  Below is an example of a basic template that could be invoked with `packer build`. It would create an instance in AWS, and once running copy a script to it and run that script using SSH.
    85  
    86  -> **Note:** This example requires an account with Amazon Web Services. There are a number of parameters which need to be provided for a functional build to take place. See the [Amazon builder](/docs/builders/amazon.html) documentation for more information.
    87  
    88  ``` {.javascript}
    89  {
    90    "builders": [
    91      {
    92        "type": "amazon-ebs",
    93        "access_key": "...",
    94        "secret_key": "...",
    95        "region": "us-east-1",
    96        "source_ami": "ami-fce3c696",
    97        "instance_type": "t2.micro",
    98        "ssh_username": "ubuntu",
    99        "ami_name": "packer {{timestamp}}"
   100      }
   101    ],
   102  
   103    "provisioners": [
   104      {
   105        "type": "shell",
   106        "script": "setup_things.sh"
   107      }
   108    ]
   109  }
   110  ```