---
description: |
  The `packer hcl2_upgrade` Packer command is used to transpile a JSON
  configuration template to it's formatted HCL2 counterpart. The command will
  return a zero exit status on success, and a non-zero exit status on failure.
layout: docs
page_title: packer hcl2_upgrade - Commands
sidebar_title: <tt>hcl2_upgrade</tt>
---

-> **Note:** This command is Beta, and currently being improved upon; do not
hesitate [opening a new
issue](https://github.com/hashicorp/packer/issues/new/choose) if you find
something wrong.

# `hcl2_upgrade` Command

The `packer hcl2_upgrade` Packer command is used to transpile a JSON
configuration template to it's formatted HCL2 counterpart. The command will
return a zero exit status on success, and a non-zero exit status on failure.

Example usage:

```shell-session
$ packer hcl2_upgrade my-template.json

Successfully created my-template.json.pkr.hcl
```

## User variables using other user variables

Packer JSON recently started allowing using user variables from variables. In
HCL2, input variables cannot use functions nor other variables and are
virtually static, local variables must be used instead to craft more dynamic
variables. For that reason `hcl2_upgrade` cannot decide for you what local
variables to create and the `hcl2_upgrade` command will simply output all seen
variables as an input variable, it is now up to you to create a local variable.

Here is an example of a local variable using a string input variables:

```hcl
variable "foo" {
  default = "Hello,"
}

variable "bar" {
  default = "World!"
}

locals {
  baz = "${var.foo} ${var.bar}"
}
```

## Go template functions

`hcl2_upgrade` will do its best to transform your go _template calls_ to HCL2,
here is the list of calls that should get transformed:
  - ```{{ user `my_var` }}``` becomes ```${var.my_var}```.
  - ```{{ env `my_var` }}``` becomes ```${var.my_var}```. Packer HCL2 supports 
    environment variables through input variables. See
    [docs](http://packer.io/docs/from-1.5/variables#environment-variables)
    for more info.
  - ```{{ timestamp }}``` becomes ```${local.timestamp}```, the local variable
    will be created for all generated files.
  - ```{{ build `ID` }}``` becomes ```${build.ID}```.

The rest of the calls should remain go template calls for now, this will be
improved over time.

-> **Note**: The `hcl2_upgrade` command does its best to transform template
calls to their JSON counterpart, but it might fail. In that case the
`hcl2_upgrade` command will simply output the local HCL2 block without
transformation and with the error message in a comment. We are currently
working on improving this part of the transformer.

## Options

- `-output-file` - File where to put the hcl2 generated config. Defaults to
  JSON_TEMPLATE.pkr.hcl