Added documentation page for environmental variables. #1130

website/source/docs/other/environmental-variables.html.markdown

+---
+layout: "docs"
+---
+
+# Environmental Variables for Packer
+
+Packer uses a variety of environmental variables. A listing and description of each can be found below:
+
+* 'PACKER_LOG' - Setting this to any value will enable the logger. See the [debugging page](docs/other/debugging.html).
+
+* 'PACKER_LOG_PATH' - The location of the log file. Note: 'PACKER_LOG' must be set for any logging to occur. See the [debugging page](docs/other/debugging.html).
+
+* 'PACKER_CONFIG' - The location of the core configuration file. The format of the configuration file is basic JSON. See the [core configuration page](docs/other/core-configuration.html).
+
+* 'PACKER_CACHE_DIR' - The location of the packer cache. 
+
+* 'PACKER_PLUGIN_MIN_PORT' - The minimum port that Packer uses for communication with plugins, since plugin communication happens over TCP connections on your local host. The default is 10,000. See the [core configuration page](docs/other/core-configuration.html).
+
+* 'PACKER_PLUGIN_MAX_PORT' - The maximum port that Packer uses for communication with plugins, since plugin communication happens over TCP connections on your local host. The default is 25,000. See the [core configuration page](docs/other/core-configuration.html).
+
+* 'PACKER_NO_COLOR' - Setting this to any value will disable color in the terminal.