Document use of TMPDIR required for remote plugin installation (#13056)

* Document use of TMPDIR required for remote plugin installation

* Update website/content/docs/configure.mdx

Co-authored-by: Lucas Bajolet <105649352+lbajolet-hashicorp@users.noreply.github.com>

---------

Co-authored-by: Lucas Bajolet <105649352+lbajolet-hashicorp@users.noreply.github.com>

website/content/docs/commands/plugins/install.mdx

@@ -18,7 +18,9 @@ HashiCorp only verifies plugins from GitHub under the`hashicorp/*` namespace. We
 
 ### Installation directory
 
-By default, Packer installs plugins into the plugins directory at `$HOME/.config/packer/plugins` on Unix and `%APPDATA%\packer.d\plugins` on Windows, but you can specify a different directory using the `PACKER_PLUGIN_PATH environment variable. Refer to the [Packer configuration reference](/packer/docs/configure) for additional information.
+By default, Packer installs plugins into the plugins directory at `$HOME/.config/packer/plugins` on Unix and `%APPDATA%\packer.d\plugins` on Windows, but you can specify a different directory using the `PACKER_PLUGIN_PATH environment variable. 
+Plugin installation requires access to temporary files under `TMPDIR`. If the system's temp directory is non-writable or non-executable, use TMPDIR to override the location of the temporary file store used by Packer.
+Refer to the [Packer configuration reference](/packer/docs/configure) for additional information.
 
 ## Usage
 

website/content/docs/configure.mdx

@@ -80,8 +80,9 @@ each can be found below:
   [Packer's home directory](#packer-s-home-directory) for more.
 
 - `PACKER_GITHUB_API_TOKEN` - When using Packer init on HCL2 templates, Packer
-  queries the public API from Github which limits the amount of queries on can
-  set the `PACKER_GITHUB_API_TOKEN` with a Github Token to make it higher.
+  queries the public API from GitHub which has rate-limits on its APIs.
+  You can set the `PACKER_GITHUB_API_TOKEN` environment variable
+  with a GitHub Token to make it higher.
 
 - `PACKER_LOG` - Setting this to any value other than "" (empty string) or
   "0" will enable the logger. See the [debugging
@@ -106,18 +107,20 @@ each can be found below:
   using the Packer's config file, see the [config file configuration
   reference](#packer-config-file-configuration-reference) for more.
 
-- `PACKER_PLUGIN_PATH` - a PATH variable for finding packer plugins.
-  This takes precedence over `PACKER_CONFIG_DIR/plugins` for plugin discovery
-  if defined.
+- `PACKER_PLUGIN_PATH` - a PATH variable for finding packer plugins. This takes
+     precedence over `PACKER_CONFIG_DIR/plugins` for plugin discovery if
+     defined. Plugin installation requires access to temporary files under
+     `TMPDIR`. If the system's temp directory is non-writable or non-executable,
+     refer to `TMPDIR` to override the location of the temporary file store used by
+     Packer.
 
 - `CHECKPOINT_DISABLE` - When Packer is invoked it sometimes calls out to
   [checkpoint.hashicorp.com](https://checkpoint.hashicorp.com/) to look for
   new versions of Packer. If you want to disable this for security or privacy
   reasons, you can set this environment variable to `1`.
 
-- `TMPDIR` (Unix) / `TMP` `TEMP` `USERPROFILE` (Windows) - The
-  location of the directory used for temporary files (defaults to `/tmp` on
-  Linux/Unix and `%USERPROFILE%\AppData\Local\Temp` on Windows Vista and above).
-  It might be necessary to customize it when working with large files since
-  `/tmp` is a memory-backed filesystem in some Linux distributions in which case
-  `/var/tmp` might be preferred.
+- TMPDIR (Unix) / TMP, TEMP, USERPROFILE (Windows) - This specifies the
+     directory for temporary files (defaulting to /tmp on Linux/Unix and
+     %USERPROFILE%\AppData\Local\Temp on Windows Vista and later). Customizing
+     this setting might be necessary for systems where the default temporary
+     directory is either non-writable or non-executable.

website/content/docs/plugins/install.mdx

@@ -27,7 +27,9 @@ Note that Packer checks the plugin installation directory against the `required_
 
 ### Installation directory
 
-By default, Packer installs plugins into the plugins directory at `$HOME/.config/packer/plugins` on Unix and  `%APPDATA%\packer.d\plugins` on Windows, but you can specify a different directory using the `PACKER_PLUGIN_PATH environment variable. Refer to the [Packer configuration reference](/packer/docs/configure) for additional information.
+By default, Packer installs plugins into the plugins directory at `$HOME/.config/packer/plugins` on Unix and  `%APPDATA%\packer.d\plugins` on Windows, but you can specify a different directory using the `PACKER_PLUGIN_PATH environment variable. 
+Plugin installation requires access to temporary files under `TMPDIR`. If the system's temp directory is non-writable or non-executable, use TMPDIR to override the location of the temporary file store used by Packer.
+Refer to the [Packer configuration reference](/packer/docs/configure) for additional information.
 
 ## Requirements
 
@@ -194,4 +196,4 @@ generate a new token.
 
     ```shell-session
     $ export PACKER_GITHUB_API_TOKEN=<token>
-    ```
+    ```