190 lines
11 KiB
Plaintext
190 lines
11 KiB
Plaintext
---
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page_title: Provisioner Connection Settings
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description: >-
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The connection block allows you to manage provisioner connection defaults for
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SSH and WinRM.
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---
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# Provisioner Connection Settings
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Most provisioners require access to the remote resource via SSH or WinRM and
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expect a nested `connection` block with details about how to connect.
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~> **Important:** Use provisioners as a last resort. There are better alternatives for most situations. Refer to
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[Declaring Provisioners](/language/resources/provisioners/syntax) for more details.
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## Connection Block
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You can create one or more `connection` blocks that describe how to access the remote resource. One use case for providing multiple connections is to have an initial provisioner connect as the `root` user to set up user accounts and then have subsequent provisioners connect as a user with more limited permissions.
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Connection blocks don't take a block label and can be nested within either a
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`resource` or a `provisioner`.
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* A `connection` block nested directly within a `resource` affects all of
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that resource's provisioners.
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* A `connection` block nested in a `provisioner` block only affects that
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provisioner and overrides any resource-level connection settings.
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Since the SSH connection type is most often used with
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newly-created remote resources, validation of SSH host keys is disabled by
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default. If this is not acceptable, you can establish a separate mechanism for key distribution and explicitly set the `host_key` argument (details below) to verify against a specific key or signing CA.
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-> **Note:** In Terraform 0.11 and earlier, providers could set default values
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for some connection settings, so that `connection` blocks could sometimes be
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omitted. This feature was removed in 0.12 in order to make Terraform's behavior
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more predictable.
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### Example usage
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```hcl
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# Copies the file as the root user using SSH
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provisioner "file" {
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source = "conf/myapp.conf"
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destination = "/etc/myapp.conf"
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connection {
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type = "ssh"
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user = "root"
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password = "${var.root_password}"
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host = "${var.host}"
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}
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}
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# Copies the file as the Administrator user using WinRM
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provisioner "file" {
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source = "conf/myapp.conf"
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destination = "C:/App/myapp.conf"
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connection {
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type = "winrm"
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user = "Administrator"
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password = "${var.admin_password}"
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host = "${var.host}"
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}
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}
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```
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### The `self` Object
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Expressions in `connection` blocks cannot refer to their parent resource by name. References create dependencies, and referring to a resource by name within its own block would create a dependency cycle. Instead, expressions can use the `self` object, which represents the connection's parent resource and has all of that resource's attributes. For example, use `self.public_ip` to reference an `aws_instance`'s `public_ip` attribute.
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### Argument Reference
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The `connection` block supports the following argments. Some arguments are only supported by either the SSH or the WinRM connection type.
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| Argument | Connection Type | Description | Default |
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|---------------|--------------|-------------|---------|
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| `type` | Both | The connection type. Valid values are `"ssh"` and `"winrm"`. Provisioners typically assume that the remote system runs Microsoft Windows when using WinRM. Behaviors based on the SSH `target_platform` will force Windows-specific behavior for WinRM, unless otherwise specified.| `"ssh"` |
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| `user` | Both | The user to use for the connection. | `root` for type `"ssh"`<br />`Administrator` for type `"winrm"` |
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| `password` | Both | The password to use for the connection. | |
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| `host` | Both | **Required** - The address of the resource to connect to. | |
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| `port` | Both| The port to connect to. | `22` for type `"ssh"`<br />`5985` for type `"winrm"` |
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| `timeout` | Both | The timeout to wait for the connection to become available. Should be provided as a string (e.g., `"30s"` or `"5m"`.) | `"5m"` |
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| `script_path` | Both | The path used to copy scripts meant for remote execution. Refer to [How Provisioners Execute Remote Scripts](#how-provisioners-execute-remote-scripts) below for more details. | (details below) |
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| `private_key` | SSH | The contents of an SSH key to use for the connection. These can be loaded from a file on disk using [the `file` function](/language/functions/file). This takes preference over `password` if provided. | |
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| `certificate` | SSH | The contents of a signed CA Certificate. The certificate argument must be used in conjunction with a `private_key`. These can be loaded from a file on disk using the [the `file` function](/language/functions/file). | |
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| `agent` | SSH | Set to `false` to disable using `ssh-agent` to authenticate. On Windows the only supported SSH authentication agent is [Pageant](http://the.earth.li/\~sgtatham/putty/0.66/htmldoc/Chapter9.html#pageant). | |
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| `agent_identity` | SSH | The preferred identity from the ssh agent for authentication. | |
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| `host_key` | SSH | The public key from the remote host or the signing CA, used to verify the connection. | |
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| `target_platform` | SSH | The target platform to connect to. Valid values are `"windows"` and `"unix"`. If the platform is set to `windows`, the default `script_path` is `c:\windows\temp\terraform_%RAND%.cmd`, assuming [the SSH default shell](https://docs.microsoft.com/en-us/windows-server/administration/openssh/openssh_server_configuration#configuring-the-default-shell-for-openssh-in-windows) is `cmd.exe`. If the SSH default shell is PowerShell, set `script_path` to `"c:/windows/temp/terraform_%RAND%.ps1"` | `"unix"` |
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| `https` | WinRM | Set to `true` to connect using HTTPS instead of HTTP. | |
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| `insecure` | WinRM | Set to `true` to skip validating the HTTPS certificate chain. | |
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| `use_ntlm` | WinRM | Set to `true` to use NTLM authentication rather than default (basic authentication), removing the requirement for basic authentication to be enabled within the target guest. Refer to [Authentication for Remote Connections](https://docs.microsoft.com/en-us/windows/win32/winrm/authentication-for-remote-connections) in the Windows App Development documentation for more details. | |
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| `cacert` | WinRM | The CA certificate to validate against. | |
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<a id="bastion"></a>
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## Connecting through a Bastion Host with SSH
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The `ssh` connection also supports the following arguments to connect
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indirectly with a [bastion host](https://en.wikipedia.org/wiki/Bastion_host).
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| Argument | Description | Default |
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|---------------|-------------|---------|
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| `bastion_host` | Setting this enables the bastion Host connection. The provisioner will connect to `bastion_host` first, and then connect from there to `host`. | |
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| `bastion_host_key` | The public key from the remote host or the signing CA, used to verify the host connection. | |
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| `bastion_port` | The port to use connect to the bastion host. | The value of the `port` field.|
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| `bastion_user`| The user for the connection to the bastion host. | The value of the `user` field. |
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| `bastion_password` | The password to use for the bastion host. | The value of the `password` field. |
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| `bastion_private_key` | The contents of an SSH key file to use for the bastion host. These can be loaded from a file on disk using [the `file` function](/language/functions/file). | The value of the `private_key` field. |
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| `bastion_certificate` | The contents of a signed CA Certificate. The certificate argument must be used in conjunction with a `bastion_private_key`. These can be loaded from a file on disk using the [the `file` function](/language/functions/file). |
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## How Provisioners Execute Remote Scripts
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Provisioners which execute commands on a remote system via a protocol such as
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SSH typically achieve that by uploading a script file to the remote system
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and then asking the default shell to execute it. Provisioners use this strategy
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because it then allows you to use all of the typical scripting techniques
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supported by that shell, including preserving environment variable values
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and other context between script statements.
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However, this approach does have some consequences which can be relevant in
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some unusual situations, even though this is just an implementation detail
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in typical use.
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Most importantly, there must be a suitable location in the remote filesystem
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where the provisioner can create the script file. By default, Terraform
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chooses a path containing a random number using the following patterns
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depending on how `target_platform` is set:
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* `"unix"`: `/tmp/terraform_%RAND%.sh`
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* `"windows"`: `C:/windows/temp/terraform_%RAND%.cmd`
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In both cases above, the provisioner replaces the sequence `%RAND%` with
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some randomly-chosen decimal digits.
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Provisioners cannot react directly to remote environment variables such as
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`TMPDIR` or use functions like `mktemp` because they run on the system where
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Terraform is running, not on the remote system. Therefore if your remote
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system doesn't use the filesystem layout expected by these default paths
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then you can override it using the `script_path` option in your `connection`
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block:
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```hcl
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connection {
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# ...
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script_path = "H:/terraform-temp/script_%RAND%.sh"
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}
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```
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As with the default patterns, provisioners will replace the sequence `%RAND%`
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with randomly-selected decimal digits, to reduce the likelihood of collisions
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between multiple provisioners running concurrently.
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If your target system is running Windows, we recommend using forward slashes
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instead of backslashes, despite the typical convention on Windows, because
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the Terraform language uses backslash as the quoted string escape character.
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### Executing Scripts using SSH/SCP
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When using the SSH protocol, provisioners upload their script files using
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the Secure Copy Protocol (SCP), which requires that the remote system have
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the `scp` service program installed to act as the server for that protocol.
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Provisioners will pass the chosen script path (after `%RAND%`
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expansion) directly to the remote `scp` process, which is responsible for
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interpreting it. With the default configuration of `scp` as distributed with
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OpenSSH, you can place temporary scripts in the home directory of the remote
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user by specifying a relative path:
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```hcl
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connection {
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type = "ssh"
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# ...
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script_path = "terraform_provisioner_%RAND%.sh"
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}
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```
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!> **Warning:** In Terraform v1.0 and earlier, the built-in provisioners
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incorrectly passed the `script_path` value to `scp` through a remote shell and
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thus allowed it to be subject to arbitrary shell expansion, and thus created an
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unintended opportunity for remote code execution. Terraform v1.1 and later
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will now correctly quote and escape the script path to ensure that the
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remote `scp` process can always interpret it literally. For modules that will
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be used with Terraform v1.0 and earlier, avoid using untrusted external
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values as part of the `script_path` argument.
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