---
description: |
    Communicators are the mechanism Packer uses to upload files, execute scripts,
    etc. with the machine being created.
layout: docs
page_title: 'Communicators - Templates'
sidebar_current: 'docs-templates-communicators'
---

# Template Communicators

Communicators are the mechanism Packer uses to upload files, execute scripts,
etc. with the machine being created.

Communicators are configured within the
[builder](/docs/templates/builders.html) section. 

All communicators have the following options:

<%= partial "partials/helper/communicator/Config-not-required" %>

## Using a Communicator

By default, the SSH communicator is usually used. Additional configuration may
not even be necessary, since some builders such as Amazon automatically
configure everything.

However, to specify a communicator, you set the `communicator` key within a
build. Multiple builds can have different communicators. Example:

``` json
{
  "builders": [
    {
      "type": "amazon-ebs",
      "communicator": "ssh"
    }
  ]
}
```

After specifying the `communicator`, you can specify a number of other
configuration parameters for that communicator. These are documented below.


## SSH Communicator

The SSH communicator connects to the host via SSH. If you have an SSH agent
configured on the host running Packer, and SSH agent authentication is enabled
in the communicator config, Packer will automatically forward the SSH agent to
the remote host.

The SSH communicator has the following options:

<%= partial "partials/helper/communicator/SSH-not-required" %>

### SSH Communicator Details

Packer will only use one authentication method, either `publickey` or if
`ssh_password` is used packer will offer `password` and `keyboard-interactive`
both sending the password. In other words Packer will not work with *sshd*
configured with more than one configured authentication method using
`AuthenticationMethods`.

Packer supports the following ciphers:

-   aes128-ctr
-   aes192-ctr
-   aes256-ctr
-   arcfour128
-   arcfour256
-   arcfour
-   `es128-gcm@openssh.com`
-   `acha20-poly1305@openssh.com`

And the following MACs:

-   hmac-sha1
-   hmac-sha1-96
-   hmac-sha2-256
-   `hmac-sha2-256-etm@openssh.com`

## WinRM Communicator

<%= partial "partials/helper/communicator/WinRM-not-required" %>